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2 4 0 T U R B O . C O M D A V E ' S V O L V O P A G E
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2 4 0 T U R B O . C O M D A V E ' S V O L V O P A G E
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page is being developed to explore and preserve some valuable
information related to high performance engine and cylinder head cooling for our Volvo B21, B23 and B230 engines. If you can help or if you have a comment or question, please email. CONTACT |
| Increased Radiator Capacity or Not? Seems like a good place to start. Skip to next section. The factory 240 cooling system was assumed to have been designed by smart Volvo engineers. The 240 chassis supported 4 cylinder (B21, B23, B230) and 6 cylinder engines (B27, B28 V6 petrol and D24 inline 6 cyl. diesel). All 4 cylinder models got the standard radiator below. All 6 cylinder models got substantially larger radiators. 6 cylinder cars got larger radiators, because more powerful engines create more HEAT.  The 240 4 cylinder standard radiator never changed from 1976 through 1993. The ultimate reason I'm highlighting this is to illustrate why I feel the Volvo did not do the right thing when they supplied this standard radiator in a more powerful Turbo Volvo. I feel that it was undersized for the expectations of this car, especially as it evolved over the years. And for many of you modified 240 owners, I feel this radiator is undersized for almost any modified Volvo which produces significantly more power than a stock B21, especially if you also have air conditioning. Maybe you don't agree with my opinion, because you're one of these people: "I've never had overheating issues with a stock radiator," or, "Volvo knew what they were doing." For these people I guess their cars were magical or they lived in a much cooler climate. I have always lived in a much warmer climate, so my turbo 240s were not nearly as magical. I'm more of a cynic and my thoughts go something like, "Volvo saved a LOT of money NOT having to change radiators for 20 plus years." The 240 standard 4 cylinder radiator used in the 1976 to 1993 240. Standard core size: 450 x 418 x 32 mm (17.7 x 16.5 x 1.25 inches)  Volvo Part Numbers: Radiator for manual trans PN 1266050, 1336169. For auto trans PN 1266051, 1336170. A tropical version was available (changes not known). Tropical with manual trans PN 1266052, 1346994. Tropical with auto trans PN1266053, 1346839. Cooling fan 400 mm diameter PN 1317465. Thermostatic Fan clutch PN 1306259 (1266574, 1266669). HD Tropical fan clutch PN 1357433. I don't know for an absolute certainty what size cooling tubes were used in these original radiators. The standard core thickness seems to have always been listed as 32 mm (1.25 inches). This correlates to two rows of tubes, each up to a max of about 14 mm wide (0.55 inch).  NISSENS used to offer an upgraded brass 3-row radiator for 240 or 740. Same overall dimensions, except thicker (about 2 inches thick). 3-row radiators almost always use smaller cooling tubes than a 2-row. There can be an improvement if the tubes are large enough. I think the Nissens tubes were about 12 mm wide (0.5 inch), which is depicted in the below image (not a Nissens photo). I have more about the Nissens 3-row below CLICK HERE.  Size really matters when COOLING TUBES are considered. Keep in mind there will always be companies offering 3-row, 4-row, etc., radiators. I think MOST people assume more rows are always better. I disagree. One claim is that more rows are always better because more tubes can equal more surface area for cooling. That idea does have some truth, but also more rows makes it harder for air to be efficient as it passes through. It can slow down the air and the air gets heated faster. The first row will get cooled pretty well, but the next rows not so much. It can be a delicate balance to promote good airflow AND good heat transfer. So study any radiator design closely before you buy and try to judge the good and the not-so-good. If they don't clearly cooling tube sizes, I suggest you insist on knowing that info before committing. The cooling tube size can make so much difference. Not so much the number of rows. . 240 with 3 row Nissens radiator below.  The 260 with B27 or B28 6 cylinder radiator BELOW was much wider. Overall size of about 17.5 inches tall x 29.75 inches wide x 2 inches deep. The core was about 16.5 inches tall x 23.25 inches wide.  Part Numbers: 260 radiator PN 464025, 464924. Tropical version (unknown changes) PN 1274053, 1274055. The 260 radiator was not interchangeable to a 240. So judging from these measurements, Volvo chose to INCREASE RADIATOR CORE AREA for 6 cylinder cars from about 292 square inches to about 384 square inches, a 32% increase. Did the smart engineers at Volvo calculate that the larger engine needed this because it developed 32% more output? More output = more heat, remember? Well let's see . . . Volvo rated the 1981 B28 6 cylinder at 153 ft.lbs torque, which comes to a 34% increase over the same year B21F with 114 ft.lbs torque (I'm using torque instead of HP because I think it's a better representation of output). In 1981 Volvo introduced the 240 Turbo Skip to next section. It came with the new B21ET (in Europe) and B21FT (in North America). In Volvo Manual TP30309, 1981 240 New Car Features, the B21F was listed with 107 HP and 114 ft.lbs. torque. The 1981 B21FT (without intercooler) was listed with 126 hp and 150 ft.lbs. torque (at 6 psi boost). The non-intercooled Turbo engine had a 32% increase in torque. (Again I'm using torque instead of HP because I think it's a better representation of output). So did Volvo make any cooling system capacity changes for the more powerful 240 Turbo? Sadly, NO. Volvo made no improvement to radiator capacity. To their credit Volvo did add an OIL COOLER to help offset higher oil temperatures from the oil cooled turbocharger. Do you think this was an engineering decision or a cost decision? I think part of the decision was undoubtedly because Volvo anticipated the new 700 models would quickly take over as lead sellers so the 240 could be retired ASAP. So I think they didn't want to spend more development money on a car that was going away. The 240, however, did not go away so soon. More info on oil coolers can be found in my OIL COOLER PAGE. Non-intercooled 240 Turbo below.  In my modest opinion, Volvo should 100% have increased radiator size for turbo cars. A larger radiator similar to the B28 would have helped immensely. If not right away in 1981, certainly this should have happened when the INTERCOOLER was conceived, which pushed B21FT output to 181 ft.lbs torque, a 59% increase over the B21F. Is my argument convincing anyone? Intercooled 240 Turbo below.  And now, by adding the intercooler, a NEW RESTRICTION had been placed in front of the radiator. More on this below.
 So why did Volvo spend money on adding INTERCOOLERS for cars that were soon to be discontinued? Skip to next section. The 1981-1983 and early 1984 240 Turbo was not equipped with an intercooler from the factory. By 1983 Volvo had high expectations that the new 700 models would take over as the primary seller, so the 240 could be retired as soon as practible. Intercoolers were becoming more known and more popular, especially since the new 1984 760 Turbo (B23FT), which was to become available in mid-1984, came with an intercooler(MSRP: $22,000). The 240 Turbo was already a lot more expensive than the non-turbo 240, so they didn't sell as many. The 1984 retail price for a 240 DL 2-door with manual transmission was $11,330. The 1984 240 Turbo 2-door manual was $16,540. In September 1983, when the 1984 240 models were in production, Volvo made a marketing decision to add FACTORY INTERCOOLERS to later production 1984 cars (beginning in December 1983). This was great news for 240 Turbo customers and for dealers, except it would place a burden on sales of non-intercooled 240 Turbos already built or still in dealer inventory. So Volvo authorized a campaign to provide intercooler kits to Volvo dealers so the remaining cars could be retrofitted. The intercooler kit was priced at $595.00 plus three hours labor at the dealer rate. I believe this was a deeply discounted price, considering the many components that came with the kit.  The intercooler was a great addition for performance, but WHAT did this do to the small radiator? Did the new intercooler add a restriction? I think the restrictive effect of an intercooler was more than nothing, but probably minimal. These intercoolers were more open and free-flowing than a radiator. THERE'S A DIFFERENT PROBLEM. According to Volvo public relations info from late 1983, which promoted the newly introduced intercooler, the turbo boost in an intercooled 240 at 10 PSI would push compressed air to as high as 300°F. Volvo was proud to announce that their intercooler was capable of reducing that temperature by 100°F. That sounds great, but it also means there's a very hot 200°F heat-exchanger in front of the radiator. Does that make it harder for the radiator to stay cool? Of course it does. I suppose their wasn't much concern about this back then, because most turbo cars weren't being driven at high boost for long periods. But I know from experience that going up a long grade in these cars while in boost definitely made the temp gauge steadily increase. This was before Volvo added the temperature compensation board to the gauge cluster to fool drivers. Is my argument convincing anyone yet? After Volvo added the intercooler, which WRAPPED around the sides of the radiator, a wider radiator would no longer be possible anyway. So they were definitely stuck with the small radiator. And by 1984-85, there was also a campaign underway to offer upgrades to replace oil cooled turbos for water cooled versions, because many oil cooled versions were failing prematurely. The addition of a water cooled turbo certainly helped with turbo longevity, but it also placed more stress on the cooling system. Was this added stress significant? I think so. It would NOT have been such a big deal if bigger radiators had been a thing. More details found below in the Water Cooled Turbo Coolant Hose section. My own gradual Cooling System Evolution. Skip to next section. Back in 1997 I bought my first 240 Turbo (with AC). Living in a hot summer climate, it struggled to run cool in warm months. Of course I made some gradual modifications to increase power, which didn't help. I was new to these cars and I clearly had a LOT to learn. I did a LOT of experimenting to see if cooling could be improved while using the stock radiator. I was told to try things like Water Wetter, which did absolutely nothing. I tried a "better" brass Nissens 3 row radiator. Overall size: 22.8 x 17.5 x 2 inches. Same size as factory except fatter.  Everything depends on the size of the cooling tubes. I believe this 3-row radiator had about 12 mm (0.5 inch) cooling tubes, which is depicted in the below example image. The Nissens was a nice looking radiator. It seemed to cool a little better, but it eventually proved to NOT be enough under hard conditions. And I know lots of you who bought Nissens units may have a different memory. I remember a lot of people back then who claimed to NEVER have overheating issues, even with a stock radiator. For a lot of these claims if you dug further you found out they meant "under normal driving conditions." Nissens sold HUGE numbers of these 3-rows, so there were obviously some people dissatisfied with the stock radiator. Here's a useful article comparing 2-row radiators to 3-row or 4-row. https://www.speedwaymotors.com/the-toolbox/mythbusting-1-row-vs-2-row-vs-3-row-radiator-cores-explained/145787 Here's a pretty basic radiator size calculator that might help for comparing different sizes side by side or by adding variables. Mostly for entertainment use. But I thought I'd share it. https://onlinetoolkit.co/car-radiator-sizing-calculator/ At some point I also replaced the fan clutch with a higher viscosity Tropical Fan Clutch. That did help some also, but it was still not enough under hard use in hot weather. Maybe you're wondering if my hopes and expectations were unreasonable. I didn't care. I wasn't going to give up. Why couldn't I have a car that could drive up a long steep grade in the hot desert with my AC on, and with a temp gauge that stayed where it should? The overwhelming consensus of every Volvo owner around was that was never going to be reality. My first all aluminum performance radiator. Skip to next section. In 2000 I built a 2.6 liter stroked engine based on a B23FT. It produced 326 ft.lbs. of torque. It needed more cooling. And through all this, I was still hearing from Volvo owners all over who were saying, "I don't have any cooling issues with MY stock radiator." Then someone suggested a better all aluminum radiator from Ron Davis Radiators in Arizona.  Ron Davis was offering high performance radiators with LARGER 1 inch wide cooling tubes (two rows). That sounded a LOT better than a small tube 3 row Nissens. So I bought one of their UNIVERSAL radiators in a similar height and width as a factory 240 radiator. This is a depiction of how two 1 inch cooling tubes look in a radiator like this.  I will say that Ron Davis made really great aluminum radiators, but they were not cheap. And they would be super expensive if a custom one was made. I saved money by buying a Chevy style radiator from their Stock Car page. These were considered UNIVERSAL radiators. It was about $350 back in 2000. Pretty reasonable I think. You'll see below when I later bought a WIDER aluminum radiator in 2012, I didn't go with Ron Davis. Why not? I did call them first. They used to list prices in their site, but all prices were missing in 2012. So I called to ask about buying a wider 26 x 16 inch universal Stock Car Chevy style. I was told the new price was $750. This was twice as much as a universal type from any other manufacturer. I asked what had changed. I was told Ron was very busy selling a lot of very high-end custom radiators for a lot of big-dollar hot rod projects and he felt he was worth a lot more than anyone else. Anyway, the 2000 Ron Davis radiator was a really good improvement over the Nissens and it did end overheating during most driving conditions. But looking back, there were still things that bothered me, like going up grades and still nervously watching the temp gauge rise. Everyone said that was normal for a 240 and I should learn to live with it. I did that for years. At one point, I thought the intercooler covering the entire front of the radiator was reducing airflow too much and making it work too hard, so I had a section on the bottom of the intercooler cut off so more air could go under it. I don't think that helped. It certainly didn't fix things. This photo below is from 2000.  During my years of cooling system trials I experimented with a number of electric primary fans (these are all shown in my Electric Cooling Fan Page). Some fans seemed to help if they were big enough, but it was never satisfying until I eventually got to a very large Ford Thunderbird Turbo electric fan and shroud I found at a salvage yard. That was another really good improvement, but after years of trying, I eventually realized I was just trying to force an enormous amount of air through a small radiator and that was not a correct way to do things. I needed to move up to a larger, WIDER radiator. I had learned an UNDER-SIZED radiator with a bigger fan was not the answer. If there was room for more radiator (and there was) then that's what I was going to do. It's time for a video. This will show how a custom aluminum radiator is built. https://www.youtube.com/watch?v=c8kq0-3PCJY Finally Graduating to a WIDER Radiator. Skip to next section. The Volvo Group A racing teams knew what was needed. They could NEVER have gotten away with the little radiator Volvo supplied? They fitted an oversized (wider) radiator, period. A little of it can be seen BELOW. How do we know how big this wider radiator was? I don't have precise size info, but we do know what the size of this big Group A intercooler (Volvo PN 1352717) and that can be used to compare. This photo is the R.A.S. Sport Volvo 240 driven by Thomas Lindström in the ETCC. This car resided at the Volvo museum in Gothenburg, Sweden.  This photo BELOW came from Björn Ohlson's 240 Grupp-A page https://240grupp-a.se/kylning/. According to Björn Ohlson's page, this larger radiator was adopted by racing teams in 1984 after they found the Volvo radiator to be useless.  This intercooler BELOW, offered by do88 in Sweden, has been created in the same dimensions as the original Group A intercooler. It has a core size of 600 x 451 x 52 mm (23.6 x 17.75 x 2 inches). So we can be pretty sure the oversized radiator they used had a similar core size. https://www.do88.co.uk/shop/volvo/performance-intercoolers/volvo-240-turbo-group-a-replica-do88-intercooler/   In 2012 I started shopping for a WIDER radiator for my 240. Skip to next section. I wanted a wider radiator, hopefully without having to get something custom made (and super expensive). After a long search, I bought this one below from Griffin Radiator in South Carolina. PN 1-55221-X, which was in their UNIVERSAL radiator section. The cost was under $300, not including some end tank fittings I had added locally. If you're wondering why I didn't return to Ron Davis, that's in the Ron Davis section above. And my cooling issues suddenly vanished under all conditions!  
With this Griffin being a UNIVERSAL radiator, it was not a perfect fit. but it saved some money. The overall size was 26 x 15.5 inches x 3 inches thick (660 x 394 x 76 mm). Core size was 21 x 15.50 x 2.68 inches (533 x 394 x 68). This radiator was about 3.5 inches wider than a stock radiator). It had two rows of 1.25 inch (32 mm) cooling tubes (which are bigger than the Ron Davis 1 inch tubes). And Griffin offers 1.5 inch tubes if more extreme was needed. 26 inches wide was a good width. It was a little shorter in height than I would have preferred. 17 or 17.5 inches tall would have been a better fit in a 240, but I was happy with it.  Here below you can see how the 2012 wider Griffin UNIVERSAL I bought looked in the car. This fan and shroud below is a Lincoln Mark VIII 18 inch brushed fan. It did a great job of pulling air, but it used a lot of amperage. A big fan is OK, but it should be controlled so it's not running hard when the engine only needs a little bit of air, which is most of the time with a nice big radiator. I eventually solved the fan control with a PWM variable speed controller CLICK HERE.  In 2022 I had Griffin build a NEW CUSTOM RADIATOR to my specifications. Slightly larger than the last one. My old one from 2012 got accidentally damaged and was leaking, so I needed a new one anyway. New size: 26.5 x 17 x 3 inches (673 x 432 x 76 mm). Core size: 22 x 17 x 2.68 inches (559 x 432 x 68 mm). The core has two 1.25 inch (32 mm) wide cooling tubes, same as the last Griffin. They offer cooling tubes up to 1.5 inches wide if more extreme cooling is needed.  This radiator is working exceptionally well. The new fan BELOW installed in 2022 is an 18 inch brushless fan with shroud, which is controlled by a standalone programmable PWM controller, which reads directly from my coolant temperature sender in the head. It only runs as fast as needed for the temperature, so it's always perfectly stable, even under very heavy use. More on all this at https://www.240turbo.com/BrushlessFans.html#JKfan 
So if you're going to ask my opinion of what to prioritize if your modifying a 240 Turbo for more power, I will tell you before you start on engine development, work on fitting a BIG RADIATOR. Don't wait to do this kind of improvement after all your other work. And don't listen to others who tell you it's OK to live with a marginal cooling system under hard use. And also try to improve the air ducting in front of the radiator. More on that below. MORE RADIATOR RESOURCES I'll add more here eventually as I find more potential choices. During my research I came across some videos about Cold Case Radiators. It seems they're also offering 2 row radiators with 1.25 inch tubes. I haven't investigated them deeply, but this company may be an alternative if you can find a radiator in a size you can use. A quick look through their available sizes in their site found very few in the 16 to 17.5 inch tall range. Their line up normally caters to vintage cars that use 19 inch tall radiators, so it's limited. And you might be tempted to look into Champion Radiators, because they advertise 3-row aluminum radiators. But judging by the comparison image below, which I took from the below video, I would not. The Champion 3-row core is smaller in thickness than the Cold Case 2-row (with 1.25 inch tubes). So Champion must be using really small tubes. Hearing "3 rows" can SOUND really tempting until you learn more. This guy found the Cold Case cooled better. Don't get fooled by what sounds nice. Cold Case CHC11 vs Champion 3 row Radiator: https://www.youtube.com/watch?v=5YDu51g9fzY  Improved Cooling Tube Efficiency? Skip to next section. Choosing a radiator with 1 row, 2 rows, 3 rows, 4 rows, etc., or one that's wider or with a larger surface area can be a hard decision, especially because you're spending serious money. I think the best answers can be found if you carefully study different designs and trying to filter out the sales pitches. It's rare that the cheap deal work out well in the end. So in most cases, accept that you won't get off cheap. My journey has taught me that shooting for the minimum cooling capacity that you can survive with or making many small improvements to an undersized system will rarely result in happiness. If you shoot for MORE cooling capacity than you think you need, I think that will work out much better. Which is better? Is THREE rows better than ONE? I used to think the answer was usually YES. But no longer.  Maybe more rows is better in some cases. If your overall size can't be made any wider or taller. But if you CAN go wider or taller, I would put that ahead of more rows. I think the positive theory for more rows is that it offers more surface area in contact with coolant. But there are drawbacks and limitations that come with fatter radiators. 1. The fatter core makes it harder for air to get through. 2. The air that gets through cools the first row well, but that efficiency decreases as the air gets hotter and the next rows don't get cooled as well. In the end, I think the first priority will often be to fit a radiator with the most surface area you can reasonably fit. If that radiator turns out to be big enough to be efficient with only one row, I think that would be great. Are there potentially more advanced radiator designs besides traditional rolled tube and fin? There are. Many of them are in use or have been in use for a long time. There are some high-tech designs used in more expensive radiators or in racing. These tubes below are often called Stuffed Tubes or Strutted Tubes. Similar to a traditional wide rolled tube, but with added metal structure (or struts) inside to potentially increase heat transfer. Many designs like this seem to be recommended only for air cooling, such as for intercoolers.  EXTRUDED TUBES Some manufacturers will use the term extruded tube, Micro-Tube or Micro-Channel. It appears tubes like this can be used for radiators or oil coolers. The examples below are all extruded aluminum tubes. Extruded tubes offer a structurally stronger design (thicker material) with more defense against external damage. Designs like this can also handle much higher internal pressures, which makes them suitable for oil coolers or for more rugged environments. This type of design is common in commercial or industrial equipment. There are design claims that a one row radiator with an extruded tube like some of these could offer the best of both worlds.  Here's an example showing how radiators using extruded tubes like above are offered for high performance cars. A company called ARC in Japan makes high-end radiators with "super-micro-tubes" for a limited number of Japanese cars. These appear to use ONE wide extruded tube, which has dividing walls to created a numner of channels. They claim to have a substantially increased cooling capacity. https://www.nengun.com/arc/super-micro-radiator   As it turns out, there are places in the U.S. who offer EXTRUDED TUBE core radiators. I can't say if this is a better option (HERE'S an opinion below that says it's NOT). If there are any useful tests comparing this to traditional thin-wall rolled tubes, I'd like to know.  C&R Radiator: https://www.crradiator.com/automotive-radiator Here's a video: https://www.youtube.com/watch?v=0-EDcEMBs28 Are there OPINIONS that say EXTRUDED TUBE radiators are NOT better for cooling? Yes. There is this opinion from DeWitt's Radiators. They point out that extruded tubes are considerable thicker than traditional thin-wall rolled tubes: 20 to 40 thousandths thick (0.020 to 0.040 inch) compared to 10 to 15 thousandths (0.010 to 0.015 inch) for rolled tubes. DeWitt's believes the thinner tube walls of traditional rolled tubes will reduce the thermal barrier BETTER, providing more rapid and more efficient heat transfer than a thicker extruded tube. https://www.dewitts.com/blogs/news/are-extruded-cooling-tubes-better If anyone comes across any useful test comparing tubes, please let me know. Perhaps if extruded tube technology allows for THINNER WALLS in the future, this opinion above might change. Formula One and Indy cars are using styles of micro-tube radiators which have many thousands of very small round tubes (as small as 2 mm). These are designed for a lot of free air flow around the tubes for aerodynamic gains. A radiator like this is also made to be extremely light and it's very easy to damage.  Here's a video with more info about F1 and Indycar radiators. https://www.youtube.com/watch?v=9rs5QMk40IQ Radiators using small round tubes is not new. Some early European car manufacturers were using designs like this 1921 Renault radiator a long time ago.  What is Good Radiator Air Ducting? Skip to next section. Your radiator needs as much air directed through it as you can get. Lots of older Volvos don't have a very good air ducting in front of the radiator and it may be worse after some modifications. When traveling at highway speeds and that 70 mph air is going through your grill, how much of it is FORCED to go through your radiator and how much is able to escape and go around it? If you remove your grill and can see openings in there where incoming air can go to the left or right or under, those places can be closed off with a little effort.  This radiator ducting photo BELOW came from Björn Ohlson's 240 Grupp-A page https://240grupp-a.se/kylning/.  This kind of thing doesn't have to look fancy like on the 240 race car above or this 740 race car below. It doesn't have to be aluminum either.  When I've done this type of thing, I've started by cutting some sheets of cardboard first to find some shapes that will fit in there. You might need multiple overlapping sheets for some places, depending on how much room there is and what obstacles are interfering. Once I have some cardboard shapes that will work, I then transfer those onto thin ABS plastic sheets. You can buy ABS plastic sheets at Home Depot or other suppliers in sizes like 24 x 48 inches (1/16 inch thick) for about $25. ABS is strong and can be cut with tin snips or strong scissors if only 1/16 inch thick. ABS can also be bent or formed with some help from a heat gun or warming in a oven to about 300° F (Hot, Use gloves). Your pieces can finally be secured with zip-ties, so they can be removed easily when working on your car. An important word about Fan Shrouds. Sometimes modifications get done and important things get left out by mistake or because of ignorance. Primary cooling fan shrouds can get damaged and sometimes don't get replaced. And so often I see images like this below with a simple puller fan and no shroud. Don't do this for a street car that needs to stay cool in traffic, etc. If this fan below is 16 inches across, you can expect to only cool a 16 inch circle on this radiator. Every cooling fan becomes MUCH LESS EFFICIENT when no shroud is present. Plan ahead to always find a way to include a proper shroud for your primary cooling fan project.  Cooling System Flow Maps B21, B23, B230. Skip to next section. This basic cooling system diagram comes from TP31311 Design, Function B204, B234 Engines 1988- , page 236.  The below unmodified cooling system maps will help you follow along with a better understanding of coolant flow. I made these coolant maps to help you understand this better. In the below unmodified map, LOCATION #1 shows the first entry of coolant from the lower radiator hose into the water pump inlet. Location #5 shows coolant exiting the rear of the cylinder head and going to the firewall. In a 240 or 740 the coolant flowing through the firewall will be interrupted by the heater valve, which is controlled by a cable in a 240 or vacuum in a 740. When the factory heater valve is set to COLD, the valve will always be closed. This closed position means no coolant will circulate there, so then no coolant can flow out of the back of the cylinder head unless the valve is open. Unmodified Factory Maps  If you have questions about the flow direction at Location #4 into the water pump, CLICK HERE.  More relevant Cooling Info Links CLICK HERE. Modification: Adding a COOLANT BYPASS VALVE. Skip to next section. CONTEXT: This discusses adding a bypass valve to bypass a normally closed heater valve in the dash. This will discuss adding a 4-port coolant bypass valve to the existing heater hose circuit to allow full-time circulation of coolant from the back of the head. There's more than one way to do this and this has been done by some Volvo owners. A bypass valve can be on either side of the firewall, depending where you find it fits best. I'll offer some ideas and share what has been discussed or used by others before. I own a 240, so please forgive me if most of my info tilts toward that car. Lots of info here is also relevant for 700-900 models. If you're curious about some example bypass valves, you can review that BELOW.  Typical 4-port bypass valve flow diagram.  Why would you want to do this? Skip to next section. There are plenty of people who think Volvo engineers were at the pinnacle of knowledge and there's no real need for improvement in an old Volvo. Those people drive completely stock non-turbo cars without AC and have no need for this page. I really believe the Volvo 240 cooling system was designed to a MINIMUM for a NON-TURBO engine without air conditioning. Should Volvo have considered increasing the capacity when they got to the TURBO cars or when air conditioning became more common? YES, but they didn't. The only increase in capacity for a turbo car was adding an oil cooler for the oil-cooled turbo (more in my Oil Cooler Page). Plus later (for some 1984 models) they added an electric condenser fan for AC cars. When turbos would later change or get upgraded to water cooled versions, would that have been a good time to increase cooling capacity? What about when INTERCOOLERS were in the planning stages? Maybe Volvo engineers wanted to, but if they did they were told "NO." After all, the cooling system was probably just fine for northern Europe. The general reasoning for doing this bypass mod is that by allowing the hot coolant to circulate out of the back of head, we can potentially improve head cooling, particularly in the rear cylinder head region where it can be known for running hotter. Turbobricks discussions have reported real world improvements using a bypass valve to accomplish this. You can read in this TB thread below about user stealthfti's success with a bypass. https://turbobricks.com/index.php?threads/8v-b230-cooling-system-modification.121189/ Specifically, steathfti went further with a more advanced modification. He also bypassed the coolant return pipe by sending hot coolant to a "Y" or "T" fitting in the top radiator hose, instead of to the rear port on the water pump. Here's a general illustration showing coolant being returned to the top radiator hose.  An invaluable excerpt from stealthfti's comments: The SOHC cooling system works well until the RPMs exceed 3200....steady state. Above 3200, the internal flow paths of the coolant inside the head . . . BCP or SCP . . . becomes too turbulent [as in too many cross-currents] to actually prevent dead zones and steam pockets. I tried LARGE radiators. I tried different thermostats. Even different brands of water pumps. The ONE thing that KEPT the coolant temp stable at 4200 RPM, regardless of ambient temps from 0°F to 100°F, was using the heater hose head outlet to bypass coolant from the back of the head to the upper radiator hose. https://turbobricks.com/index.php?threads/8v-b230-cooling-system-modification.121189/ [NOTE: Thomas Fritz, AKA: stealthfti, passed away in 2018] WATER PUMP REAR PORT. Skip to next section. This more advanced step above is NOT required if you're just adding a valve to bypass the heater valve, however if the modifications involves deleting the heater return pipe, then you may find it necessary to block off the rear port on the water pump. A blocking plug like this below can be sourced or created. This plug below was a 2-piece part made by Volvo to fit early or later water pumps. It's a tapered rubber plug with a steel retainer to hold it in. The rubber plug insert is PN 418571. The cover plate is PN 1219915. If Volvo parts are not available, a plug could be made by using the end of an old water pump pipe and then sealing it off. Or there are tapered/conical rubber plugs available in many different sizes online if you want to look into creating your own.  This plug was commonly used for marine engines, as shown on this Volvo Penta pump PN 1378809 below for AQ131 (same as a B230 pump).  Did racers block off this rear port in Group A racing 240 Turbos? NO, they did not. Because they added one of these. GO HERE FOR MORE. 
These photos came from Björn Ohlson's 240 Grupp-A page https://240grupp-a.se/kylning/. If you need dimensions of this back port, here are some photos below. Dimensions are the same for all pumps.    Selecting a BYPASS VALVE. Skip to next section. This first 4-port bypass valve below has a VACUUM DIAPHRAGM to cycle it OPEN or CLOSED. If vacuum is present the valve will be closed. This valve is ONLY either OPEN or CLOSED. It does not appear to have a partial open function. This type of valve is discussed further in this Turbobricks discussion below for use in a 700 model. A vacuum controlled valve may or may not be appropriate for a 240. You'll have to make that decision if you feel that a such a valve is right for your car. https://turbobricks.com/index.php?threads/7-9-updated-heater-control-valve.246617/.  AFTERMARKET PART QUALITY NOTE: Having a quality, leak free valve is super important. A leaky one will not be worth the trouble if it saved you a few dollars. The above TB discussion discovered some cheap valves that people found would begin leaking eventually.  Other 4-port bypass valves. You can also find manual cable actuated bypass valves. This one is made by Thermotion PN 25-1018 and is offered by Old Air Products. Any cable valve and many electric ones can be made to open partially if that's useful.  This electric valve is from CJ Pony Parts. This can be opened or closed (or partially opened) using a variable adjusting knob.  This one above is available at https://www.cjponyparts.com/heater-bypass-valve-kit-servo-controlled-bronco/p/BHV4/ Restomod Air has a similar 4-port valve: https://restomodair.com/shopproducts/4-way-electronic-bypass-water-valve-kit/ Questions about the Water Pump TOP PORT. Skip to next section. Before I began studying this closely, I had assumed the water pump TOP PORT (#4 below) flowed out of the pump and up into the cylinder head. Apparently lots of other people had this assumption. This is incorrect. The water pump top port is a suction port and it flows down from the cylinder head. Volvo refers to this #4 port as a BYPASS in manuals. It's called a bypass because it bypasses the thermostat when the thermostat is closed, so water entering the head during warm up can still leave the head. If you want to see more about this see THERMOSTAT FUNCTION.   Here are some images of a genuine Volvo B230 water pump (PN 3547559). You can see there is a wall separating the impeller chamber from the top port, rear port and the main inlet. This means the top port, rear port and the main inlet are all suction ports. The only outflow or pressure port on this pump is the area immediately surrounding the impeller, which directs coolant into the hole on the front of the engine block.   Comparing a B21/B23 pump to a B230 pump. Skip to next section. B21, B23: PN 270681. B230: PN 271975, 271830, 271275, 270559, 1326342 Other than the bolt pattern being different, the easiest way to quickly identify which is which is the location of the bolt hole for the heater return pipe. The hole on an early pump is up high. The hole on a later pump is down low.  Here's the hole in front of the block. This hole leads to the water jacket and up to the coolant passages between the block and cylinder head. There's also a second smaller hole up and to the right. I think that may be an air bleed for the pump impeller chamber.  How big is that block coolant passage above? I've seen some reference to about 33 mm (about 1.25 inches). I think that may be WRONG. The below measurement I took from a B21 water pump suggests 27.5 mm.  Comparing different IMPELLERS: GMB versus Hepu Pump. Art Benstein wrote a comparison page at https://cleanflametrap.com/wasserpumpen.html. The more solid Hepu impeller is considered to be the closest to what came on a factory Volvo pump. Over the years the general opinion has been that the Hepu was better than an open blade impeller. Is it better? I don't know. GMB is a Japanese company and pumps are made in Japan, South Korea and Thailand. Hepu pumps are made in Germany.  Understanding how a Volvo water pump works was important in my curious mind. It's a centrifugal pump, which is very unlike a positive displacement pump. A positive displacement pump can use sprockets or pistons to draw fluid in and then push it out. These work well if high pressure is needed. A good example of a positive displacement pump is the oil pump in your engine, which has sprockets to pressurize oil. A centrifugal pump uses an impeller to spin the fluid outward against the outer walls of the impeller chamber. The impeller does not push fluid as you would imagine a propeller can. The impeller can push fluid at various speeds with less risk of over-pressurizing, but it becomes very important to make sure any and all air pockets are eliminated from an impeller system. An impeller cannot create a vacuum or suction in absence of liquid. It must be "primed". This type of pump will not move or suck coolant if the impeller is dry. Watch the video. Centrifugal Pump Basics https://www.youtube.com/watch?v=Vhc-hEjh12I Understanding Thermostat Function. Skip to next section. This image comes from TP30163, Engines 240 1975-85, page 82.  Volvo thermostat part numbers: 71° C (160° F): (non-Volvo, 273460/71); 82° C (180° F) PN 273460; 87° C (189° F) PN 273459; 92° C (197° F) PN 273307. Here are some images below showing the B21/B23 or B230 thermostat and the thermostat port where it gets mounted on the head. Once coolant enters the engine block from the pump, it travels up into the cylinder head through the coolant passages between the block and head. Once in the head, it circulates and eventually exits through the thermostat and out to the top radiator hose. NOTE the bleed valve near my thumb below should be positioned to about 12 o'clock to promote venting of trapped air in the head.  Below we can see the thermostat port is divided inside. There are two separate channels, a center channel and a right channel. The RIGHT CHANNEL leads to the head main cooling jacket. The CENTER CHANNEL goes down to the port on the bottom front of the head. This is the port which seals the head against the top of the water pump.  To satisfy my curiosity, I injected water though this center channel, which confirmed what I thought. And in the photo below I also shined a flashlight up into that bottom port, which can be seen shining through from the top.
Volvo refers to this bottom front head port as a BYPASS. It's called a bypass because it bypasses the thermostat when the thermostat is closed (only when it's closed). I took a few measurements of the thermostat port. The center channel port has a flat surface which is about 19 mm below the head surface. That'll be explained next.  Let's go back to the thermostat. That plunger in the center is what closes off coolant until the thermostat heats up and opens. These photos below show it upside-down. On the part that points toward the head there's a flat round disc, which is somewhat spring-mounted. When installed, this disc points directly at the center channel port mentioned previously. When the thermostat is COLD, that disc sits about 10 mm below the head surface and about 9-10 mm away from closing off the center channel port. At this cold temperature the CLOSED thermostat will allow coolant to flow through the center channel and down into the water pump to be recirculated. This recirculation continues during initial warm-up.  For these images I dropped the thermostat into hot water. As it becomes hot, the plunger opens and also that spring-mounted disc extends out to a new position. As it extends out, it will eventually close off the center channel.   Here's an image BELOW of the plunger as it becomes HOT and OPEN, which allows coolant to flow out of the head into the top radiator hose.  In summary, when the engine is COLD and the thermostat is CLOSED, coolant freely flows through the #4 PORT and into the pump, where it can be recirculated. Volvo refers to this port as a BYPASS in service manuals. When the engine is WARM and the thermostat is OPEN, the #4 exit is CLOSED OFF by the thermostat disc sealing the center channel closed. So when warm, all coolant flowing out of the head comes out through the thermostat and only the thermostat, unless of course some flow is also allowed out of the heater hose port at the back of the head.  Relevant Links: https://turbobricks.com/index.php?threads/7-9-updated-heater-control-valve.246617/ https://turbobricks.com/index.php?threads/8v-b230-cooling-system-modification.121189/ https://cleanflametrap.com/wasserpumpen.html https://240grupp-a.se/ Relevant General Cooling System Information Cooling System Basics: https://www.c1pulleys.com/pages/cooling-system-basics The Cooling Bible: http://www.billavista.com/tech/Articles/Cooling_Bible/index.html B21, B23, B230 Water Pump Pulleys Skip to next section.
Early water pump pulleys for 4 cylinder Volvos (1976-1984) seemed to be found as only one part number and one size. These are slightly smaller than the larger B230 pulley. The B21/B23 pulley can be identified by its lack of reinforced metal (as shown below). It's believed the lack of reinforcement might have contributed to some failures, possibly if the fan belts were overly tightened (more failure info HERE). This could be why the B230 pulleys were reinforced when they were introduced in 1985. The B230 pulley below has a 138 mm diameter. It was generally fitted to non-turbo 4-cylinders (the smaller pulley is further below).  Above photo taken from https://turbobricks.com/index.php?threads/differences-in-water-pump-pulleys-b21-b230.323223/, photo modified by me. The below washer (or spacer) was available from Volvo Penta (PN 463301). It may have been available to reinforce early pulleys.  Beginning in 1985 for B230FT turbo engines, Volvo installed a smaller pulley with a 117 mm diameter. This one was reinforced too. It's thought the smaller pulley was intended to improve engine cooling at idle on turbo cars by spinning the pump faster (18% gain). There are some opinions (GO HERE FOR MORE) that the higher pump speed can promote impeller cavitation at elevated RPMs (above 3200 RPM), potentially reducing cooling capacity, also possibly at sustained higher RPM highway cruising. Also there are opinions that the smaller pulley has potentially contributed to coolant over-pressurization at very high RPMS, being blamed for popping freeze plugs or damaging heater cores.  Above photo taken from https://turbobricks.com/index.php?threads/water-pump-pulley-diameters.374577/, photo modified by me. Early and later pulleys are mostly interchangeable, except a SMALL later pulley will not fit on an early B21/B23 water pump, because the early style pump structure interferes with the inside of the small pulley. Relevant Links or Discussion Threads https://240grupp-a.se/ https://turbobricks.com/index.php?threads/water-pump-pulley-diameters.374577/ https://turbobricks.com/index.php?threads/confirming-size-differences.367875/ https://turbobricks.com/index.php?threads/water-pump-pulley-compatibility.363061/ https://turbobricks.com/index.php?threads/differences-in-water-pump-pulleys-b21-b230.323223/ https://turbobricks.com/index.php?threads/cooling-system-changes-for-high-rpm-use.218895/ GROUP A Cylinder Head Cooling Hole Modification Skip to next section. This cylinder head modification has been around for a long time and was reportedly used for ETCC racing Volvo 240s in the 1980s. I don't think this mod is fully understood by us enthusiasts. Most explanations (including the below video) discuss using a head gasket as a template to locate the FIVE NEW HOLES holes to be drilled for better cooling (with three of those holes being along the EXHAUST SIDE).  Above cylinder head image is from https://ozvolvo.org/d/9617-530-531-head-porting-and-polishing/19, photo modified by me. I added the hole size info to this image above. That info was taken from the BELOW VIDEO. The same hole sizes are referenced in Stoni's World head work page: https://www.stonis-world.com/headwork.html NOTE that there is ONE EXTRA HOLE marked on this head above. It's on the INTAKE side of cylinder #1. It's hard to see at first. Coincidentally this hole is also present on a head gasket. Most modifications like this seem to add only 5 holes. This extra hole suggests some people have been drilling 6 holes. Further down you see that Peter Linssen added this 6th hole to his racing head too. A compelling question that came up in my mind concerning the three holes along one side. Some of the old 240 Turbo Group A images clearly show these three holes are drilled on the INTAKE side, not the EXHAUST side as seen above. So far no explanation has been found for a preference for either side. At the same time virtually all other images I have seen, including the ABOVE image, show these holes drilled on the EXHAUST side. Putting holes along the INTAKE side might be slightly more difficult, because it doesn't appear any head gaskets have all those holes on the intake side to use as a template. For example, this image BELOW was posted in the 240 Grupp-A page https://240grupp-a.se/kylning/ and it shows holes drilled on the INTAKE side. Can anyone offer an explanation?  If I was to offer an uneducated opinion, I think maybe I would choose to make these holes on the HOTTER EXHAUST side. But maybe someone thought because of the engine tilt, the holes might be better in the higher elevation INTAKE side? I welcome your comments. This short VIDEO below offers an explanation of how these holes can be added. Skip to next section. Group A 240T Head Cooling Mod. https://www.youtube.com/shorts/qqn_xvRclG0
Relevant Links or Discussion threads: https://turbobricks.com/index.php?threads/8v-b230-cooling-system-modification.121189/ https://ozvolvo.org/d/9617-530-531-head-porting-and-polishing/19 https://www.stonis-world.com/headwork.html https://turbobricks.com/index.php?threads/are-people-still-doing-the-grpa-cooling-mod.382897/ https://240grupp-a.se/kylning/ This image below has been around for a long time. It's from Bilsport Magazine Nr 10, 2001, page 27 (in Swedish). It very lightly discusses adding the Group A cooling holes (on the exhaust in this image). I added an English interpretation below, however it offers very little help.
This is Page 14 from the Volvo 240T Group-A Owner's Manual, by Richard Prince. Skip to next section. Note that the image in this page, originally from Björn Ohlson's 240 Grupp-A page, shows the three holes drilled along the INTAKE side. A link to the entire Group A Manuel is a bit further below CLICK HERE.  The above Cylinder Head page mentions that Group A heads were also modified by blocking off the water pump port by inserting a "welch" plug in the head (same thing as a freeze plug). Also it speculates that this reverses the flow through the head. NO! It does NOT reverse the flow. Blocking this port simply stops coolant from flowing from the head down to the water pump top port. This flow was a factory function during warm-up, used when the thermostat was cold and closed. Installing a "welch" plug as mentioned is a logical modification for a race car that no longer needs the factory warm-up function or a traditional thermostat. This port in the head was also detailed in a previous section. In a factory engine, coolant flows from this port down into the water pump when the engine is cold. Then this flow becomes closed off by the thermostat when it gets warm (more detailed thermostat explanation HERE).  These comparison photos BELOW (also found in Björn Ohlson's 240 Grupp-A page https://240grupp-a.se/kylning/) show that some serious porting was done to open or blend the thermostat channels.  U-Bend Pipe for the Water Pump. Skip to next section These images BELOW were found in Björn Ohlson's 240 Grupp-A technology page at https://240grupp-a.se/kylning/. They show a custom U-bend pipe made for a Group A 240 Turbo. It's purpose was to be inserted into the water pump REAR port where the heater/coolant return pipe would normally be on a factory engine.   As seen in the next photo BELOW, this U-bend pipe was made to bring water into the water pump rear port from the expansion tank mounted above. When I first saw this, I have to say I was puzzled. I could see that bringing in some extra water from the expansion tank, which holds water from the cold side of the radiator, would not be a bad thing. The Grupp A page only described it's purpose as "for increased water flow." This pipe looks to be quite an effort to create. In my limited understanding, it appeared to me that a far easier alternative would have been to add a TEE FITTING into the lower radiator hose next to the pump. The water would flow into the same place. I don't know if adding the U-bend pipe makes that extra water flow any better than a TEE fitting would. This TEE below is made to fit the lower radiator hose, Volvo PN 1378548.  If this was done and the rear water pump port had no use, the back of the pump can be simply blocked off LIKE SHOWN in THIS SECTION. This special U-bend pipe has been found in photos of virtually every Group A 240 I've been able to find photos of, so it was obviously universally well-regarded as a worthwhile modification across all teams. So this makes me think someone developed technical information about it and all of the Group A 240 teams had access to it. Otherwise I don't know how this pipe came to be. I have NOT found this pipe mentioned in any FISA 240 homologation documents, in Volvo R-Sport Competition catalogs, or in the 240T Group A Owner's manual. The origin of this pipe is a mystery to me so far. Who designed it and does any documentation exist? This pipe has also been added to replica Group A 240s, such as up to eight of them created by Peggen Andersson and GDM Motors in Belgium around 1999 to 2022 (https://www.hagerty.co.uk/articles/news-articles/volvo-240-flying-brick-replicas-to-storm-the-track/). Image BELOW from Björn Ohlson's 240 Grupp-A page at https://240grupp-a.se/kylning/.  While no info exists for this pipe other than it's there for "for increased water flow," an added THEORY has occurred to me. Perhaps it's further purpose was to REDUCE potential PUMP CAVITATION at high speeds: When the engine runs at high speeds, the water pump spins really fast. If it's too fast, the high speed of the impeller can create a severe drop in pressure which begins at the eye of the impeller. Vapor bubbles begin forming in the impeller chamber and this effect will displace the water (this is CAVITATION). Because vapor bubbles transfer heat well at all and it's hard for water to get pushed through it's circulation, coolant flow drops off severely and the the engine cooling suffers. Race cars typically use ONLY WATER for cooling, because a spill on the track is much less of a problem. Water has a higher vapor pressure than a 50/50 mix of antifreeze, so this effect is worse with pure water. Since the Volvo water pump has a centrifugal impeller, the the impeller must always be absolutely fully submerged and well fed to remain efficient. Perhaps high speed impeller cavitation was a recognized problem by the the Volvo racing teams. Perhaps this U-bend pipe was a way to improve water supply to the impeller; To ensure the pump is always well fed from an ADDITIONAL SOURCE ABOVE THE PUMP, rather than relying on only the SUCTION OF WATER up through the lower radiator hose. This photo BELOW shows another U-bend pipe arrangement with the expansion tank much further away near the intake manifold. This is a Sportpromotion "LUNA" Group A 240 built by Magnum Racing.  This car BELOW is one of FOUR Group A 240's contracted by Volvo to be built for the 1985-86 ETCC season. Only two of them still exist. One, built by Magnum Racing, resided in the Volvo Museum in Sweden. This one below, built by Volvo Motorsport was driven by Ulf Granberg and Anders Olofsson and in the late 1986 season by Mauro Baldi and Peggen Andersson. The Nordica cars were managed for Volvo by RAS Sport in Belgium. The U-bend pipe can be seen if you look closely. This car was owned by Peggen Andersson up to 2017. The current owner is not known.  Here's another image BELOW. Again the expansion tank pipe is flowing down to the pump rear port. This photo below shows the R.A.S. Sport (Nordica) 240, which was driven by Thomas Lindström.  Plus an interesting separate note in this photo: If you notice the small radiator over-flow hose, it's mounted up through the radiator support. I don't know for certain, but it looks like it might have a cap on a valve. With the way this expansion tank is plumbed, filling that tank would not fill the radiator. There is no radiator cap on the radiator or any other fill access without opening the top radiator hose. So perhaps this overflow hose fitting is for topping off the radiator quickly in the pitts.  The complete 32 page GROUP-A MANUAL (pdf) can be found at https://1drv.ms/b/s%21AtjXfjFx5NHNjakt9r9kaL2_GeVI9Q  More Related Performance Cooling Mods Skip to next section. Peter Linssen (co-founder of MVP and later owner of The V-Shop in Portland Oregon) owned a 1985 740 Turbo (manual transmission), which was first modded as a powerful daily driver and then years later into a very powerful race car. The second pic below was taken in 2004 at Thunderhill Raceway in Willows, California following the 2004 Davis Volvo Meet.   Here it is below during the 2007 Davis Volvo Meet.   Then these pics below were taken at the 2012 iPd Garage Sale.  Peter eventually retired years later and sold the car. More photos and some great commentary can be seen in the Bring a Trailer sale in 2025: https://bringatrailer.com/listing/1985-volvo-740-6/  Peter did a lot of experimentation and development with this car so it could stay cool during high speed endurance racing in warm weather while producing 500 hp. One such experiment was described in the below linked 2007 TB discussion thread where the below cylinder head images were shared. The success of this bypass mod is not known to me, but the reason for showing it and for referencing the below TB thread is to share ideas for those who might want to know about experiments like this. We should not be afraid to try new things to see what works for your car. Ignore the internet trolls.   In this thread below, TB member stealthfti mentioned that he had done something similar, except that he had terminated the hose into a "T" or "Y" fitting in the top radiator hose. Stealthfti reported he had tested his modification extensively and he felt STRONGLY that it was a success and he offered compelling comments. NOTE: There are a lot of photos missing in this thread, so reading it will require using your imagination in some places. https://turbobricks.com/index.php?threads/8v-b230-cooling-system-modification.121189/ Perhaps stealthfti's idea of using a "T" or "Y" into the radiator top hose offered a better solution to promote positive flow in the direction it was intended. If you consider how Volvo originally intended that back heater port on the head to be plumbed, it normally returns coolant to a SUCTION port on the back of the water pump. So we need to consider how mods like this will affect coolant flow. This bypass hose mod Peter did above has not appeared in any later photos of his car. Perhaps Peter abandoned this idea and did something different. Did you spot the Group A holes? You can spot the Group-A cooling holes which were added to this head. TWO holes at the back, THREE holes added along the EXHAUST side), PLUS there's a SIXTH HOLE drilled on the INTAKE side near cylinder #1 intake valve. This extra 6th hole is also found on a head gasket.  Comparison of a BCP versus SCP head Skip to next section. Here you can see the difference between a BIG COOLANT PASSAGE (BCP) head and the more desirable SMALL COOLANT PASSAGE (SCP) head.  The BCP head at top is a 160 head. The SCP head is a 530. Why is the Small Coolant Passage head considered better? It's considered to be a stronger design, sealing better at the head gasket when under high stress or high boost, and it's potentially less prone to cracking. When did this coolant passage change occur? One Turbobricks member wrote: "I have a 398 BCP head dated 3/3/84... and a 398 SCP head dated 4/12/84." I also have a 398 SCP head I pulled from a Pick-A-Part that is dated 4/4/84. Apparently this change occurred between March 3 and April 4, 1984 (at least for 398 head). Where can you find the date code? It's molded into the head on the exhaust side very close to the back as shown below. The numbers are vertical (Day - Month - Year), i.e.: for a 12 April 1984 head the numbers appear as 12 then 4 then 84 at the bottom. This date code example below is a BCP 160 head with a date of 23/4/83 (23 April 1983).  Oil Cooled or Water Cooled Turbocharger? Skip to next section. Here are some example turbochargers. The left turbo is oil cooled. The right turbo is water cooled. On this water cooled turbo the water fitting is a banjo type.   Here are some fairly typical banjo fittings for a water cooled turbo.  Beginning in 1981, when the Volvo 240 Turbo was introduced, it originally came with an OIL COOLED turbocharger. If a turbo is not water cooled, then it relies on oil circulation to cool it. The truth is all turbos rely on oil circulation for lubrication and oil has cooling properties, so even a water cooled turbo is oil cooled too. Volvo upgraded all 240 Turbos with an oil cooler mounted next to the radiator, which helped cool the oil for the turbo. It was fairly common for an oil cooled turbo to fail prematurely in a 240 Turbo in the 1980s. When turbos were replaced, many of them were upgraded to water cooled types. Most of these retrofits were done at Volvo dealerships. Coolant fittings (pipes) and coolant hoses were added (these are discussed BELOW). These failures don't necessarily mean that an oil cooled turbo is less durable. A turbo can fail for a number of reasons, but there are some potential failure causes that can be attributed to high heat, infrequent oil changes, and oil coking. Oil coking occurs in the hot oil passages when super-heated oil cooks and and then slowly forms hard deposits as it cools off. The problem was made much worse when Volvo owners didn't allow the turbo to cool down before shutting off the engine. Eventually these deposits can build up and choke off oil feed passages and damage bearings inside the turbo. Volvo recommended that drivers never quickly shut off a hot turbocharged engine. Instead they recommended that a turbo engine should be allowed to idle for a while to cool down first. This is the best way to keep coking from happening. Also more frequent oil changes helps. For the 240 Turbo, Volvo recommended oil and filter changes at 3,750 mile intervals, instead of 7,500 for non-turbos.  Above image is from Volvo manual TP30309, 1981 240 New Car Features, pg 45. Here are the hose TEES Volvo used for a 240 to upgrade to a water cooled turbo. PN 1378548 is the larger one for the lower radiator hose. PN 1378420 is the smaller TEE placed below the expansion tank.  Is a Water Cooled Turbo Bad for your Cooling System? There are opinions that say a water cooled turbo is a detriment to your cooling system because it sends hot coolant directly back into the engine. This is a valid point. The extra heat in your coolant makes it harder to cool your engine. So in my humble opinion, Volvo really should have increased the cooling system capacity to compensate for turbo cars (more than just adding an oil cooler). More power always makes more heat, but Volvo didn't give the 240 Turbo anything extra for coolant. They left a cooling system in there made for a basic non-turbo, originally designed for a non-AC car. This under-developed system might not be enough if you're car is modified. This of course depends on the environment and if air conditioning is also pushing the system. A Discussion of Turbo Coolant Lines. Skip to next section. I've seen pretty much zero informative in Volvo service manuals discussing coolant hose or pipe routing for a Volvo water cooled turbo. The 240 Turbo originally came with an oil cooled turbo, but I know upgrades to water cooled turbos were done by Volvo dealerships after a plaque of failed turbos. And water cooled turbos later became standard in 740 Turbos. I suspect the 240 information came out in service bulletins, but I haven't seen it. With very little information, figuring this out can be confusing for Volvo turbo owners, so I made this diagram below from my own observations. The coolant circulation is passive and we can hope negative pressure from the lower radiator hose suction effect will help keep circulation moving in the direction needed. Original Coolant Pipe Routing.  A note of interest: It really doesn't matter which fitting on the turbo goes IN from the expansion tank hose and which goes OUT to the lower radiator hose. Coolant can flow either direction through a turbo. As already mentioned, there are NEGATIVE aspects to having water cooling hoses on a turbo. It's good for the turbo, but not so good for the engine. The good part is the turbo will always get cooler coolant from the cold side of the radiator, but allowing hot coolant from the turbo to enter the water pump and go back through the engine is not so good. If your cooling system is large enough to handle the extra load or if you're confident your engine won't suffer from hot coolant injection, then it might be OK. If you're not so OK with it, it is possible to improve this. See the next diagram below. Bringing an Electric Booster Pump into the discussion. Skip to next section. If you do any online research into Volvos using Electric Water Pumps or Booster Pumps in places like TB, you'll find very little. The reason for this is NOT because it hasn't been asked or discussed. It has. The reason is that over the years when someone did ask, almost all of the responses were from short-sided people (I'm trying to be extra nice) who didn't actually know sh*t; "That's for drag racing only," or, "That's not reliable and there's NO reason ever to not use the factory pump." Those were real comments. Maybe those people should do more research before spouting off with BS. The hyperbolic hostility almost always resulted it the discussion being shut down. Maybe you can use this to GUESS why I almost always choose to post my research in my own pages instead of in discussion threads. Please keep in mind that BMW has been using Electric Water Pumps and Electric Booster Pumps since 2006. Mercedes almost as long. Lot's of other cars have them too. In this section I'm proposing adding a small electric booster pump (EBP) near the expansion tank with the purpose of creating positive coolant flow through the turbo. I think it would be difficult to get satisfactory flow as shown below without a small pump to boost flow. Here I've changed the final exit of coolant from the turbo to a TEE in the TOP RADIATOR HOSE. That seems like a proper place for hot coolant to go. Going further, this offers a nice opportunity to add a temperature sensor in a location that would allow a pump controller to regulate pump speed or frequency. And it would certainly be a nice benefit if such a controller ALSO allows the pump to continue running for a few minutes AFTER ENGINE SHUTDOWN. Would that make things better? Yes, I think it would. If you prefer, this can be considered experimental until someone shows it being done. I have not actually done this, but I'm 100% convinced it would assure your turbo is happier and your engine would get ONLY nice, cool coolant from the cold side of the radiator. Modified Pipe Routing.  Intro to the EBP. Skip to next section. Here I'll show you some info I've gathered on small Electric Booster Pumps (EBP). Electric booster pumps are sometimes also referred to as electric water pumps. Sometimes they can be the same thing, but for this discussion I'll insert a distinction. For this, a 12 volt DC booster pump will be considered something that's smaller and more compact that a typical electric water pump (EWP). The fluid demand and capabilities will also be quite different. Sometimes you'll come across intercooler booster pumps for water to air intercoolers. These can usually be considered the same as an EWP and they can widely vary in flow capabilities. Example size comparison: BOOSTER versus WATER PUMP.  Larger electric water pumps are often rated for flow output in liters per minute (l/min), but sometimes also in liters per hour, gallons per minute, etc. A dedicated EWP installed to replace an existing mechanical water pump might have a flow in the range of 100 to 160 liters per minute. A small booster pump might be rated for only 1000 liters per hour (l/hr). This would equal 16 l/min, quite a bit less compared to 100 l/min. So a small BOOSTER would not be appropriate to keep your whole engine cool, but it certainly can be used to circulate coolant in turbo hoses. A large EWP would be overkill for a small booster job. Most larger EWPs will have IN and OUT ports that are around 32 to 51 mm diameter (1.25 to 2 inches). A small booster pump might have IN and OUT ports that are only 19 to 22 mm (3/4 to 7/8 inch). A booster pump usually needs to fit in a smaller space, so we should talk about size and weight. Many EWPs can weigh from 2 to 3 lbs. and often a larger brushless EWP (below) can be heavier, sometimes 4 to 5 lbs. Many booster pumps can weigh between 0.7 lb. to 1.3 lb. For these example images below I've included some pumps from Davies Craig to show size comparisons. Below a Davies Craig EBP23 booster is shown next to an EWP150 water pump. Davies Craig is not the only source for these things, but they can be a pretty good place to start looking and use for comparison.  And below we have a larger Davies Craig EWP180 Brushless Water Pump.  Has an Electric Booster Pump been used in an older Volvo? Skip to next section. Yes. I'm aware of one. It was not used for cooling a turbo though. In 2012 Nathan (TB user nathaninwa) shared in the below discussion threads a very small bit of info on the addition of an electric water pump and an electric booster pump for his B230 16 valve turbo engine. The booster pump info from his thread will be shared here. The EWP info will be shared later. https://turbobricks.com/index.php?threads/941g-16v-turbo-build.199503 https://turbobricks.com/index.php?threads/electric-water-pump-on-b230.272309/ Nathan used this booster pump to boost the coolant flow coming out of the back of the cylinder head, through the heater core and then back to a port mounted in a custom freeze plug in the block. Sorry, that's all he provided. The reason the coolant in this example did not return to the water pump pipe and to the back of the mechanical water pump as it would normally was because his mechanical water pump had been eliminated.  It took some searching, but I eventually identified this booster pump. It's a Bosch PN 204-835-03-64 auxiliary pump used in a number of Mercedes Benz cars from 2008 to 2025. Another part number is Bosch 2115060000. The only on-line listing from Bosch I've found is here. Not much info other than photos.: https://www.boschautoparts.com/p/water-pumps-0392023004- Here's what I've managed to find. This 12 volt Bosch pump has a brushless motor (with a 2-pin wire connector). It weighs about 0.7 lbs. It draws 0.7 Amps. Operating Pressure (PSI) 1.45. Flow: 4 GPM (15L/Minute). The mating 2-wire connector will be TE 967412: https://www.te.com/en/product-1-967412-2.html  This spec sheet suggests this pump was available from Davies Craig at one time. https://dalhems.com/f/d/eb99b31725204494a06e9b9200f9beb9/EBP_Installation_Instructions.pdf And in the Davies Craig 2016 catalog it was listed as EBP15. https://outlawspeed.com.au/shop/media/wysiwyg/files/brand_catalogues/DaviesCraig_EWP_2016_Catalogue.pdf It's still available and can be been found at a number of places. https://www.fcpeuro.com/products/mercedes-engine-auxiliary-water-pump-2118350264-2118350265 https://www.germanautoparts.com/bosch/auxiliary-water-pump/204-835-03-64 So a booster pump like the above Bosch might be an option. Your decision will also depend on how it'll be controlled. Just wiring a pump to run all the time is not the way. It'll should have some sort of device to control it, based on when it should come on and for how long. One option is a DC Relay Controller as shown below. Since this pump has a 2-wire connector, it should be clear (even though it has a brushless motor), that this pump can only be run ON or OFF. A brushless motor with two wires is activated the same way as a normal brushed DC motor using a relay or relay based controller. It does not run as a variable speed pump the way a more modern PWM controlled brushless pump can. That doesn't make this pump a bad choice. This pump draws very, very little current (not like a big pump does). If a controller is set up to turn this pump on/off at intervals using a coolant temperature sensor, you'll probably never notice it running. If you need a suggestion for a temperature based 12v DC relay controller that can run a pump like this, this one can do the job very inexpensively. It comes from the same place (https://gkgoodcheapparts.com) as the PWM brushless fan controller I installed for my 240 (details of that in my Brushless Fan Page HERE). https://gkgoodcheapparts.com/products/widget-man-fdm2-self-learning-dc-fan-relay-controller   If a true variable speed pump using PWM signals for speed control is more like something you need, I'll cover that next. Variable Speed Brushless Booster Pumps Controlled using Pulse Width Modulation (PWM). There are a number of choices out there. Sometimes models come and go. I'm going to highlight a couple for now to help explain. This EBP is Bosch PN 039202453G. It's a brushless pump with a 3-pole connector. The S-pin in the connector controls the pump speed using a PWM signal, pretty much exactly the same way as a brushless cooling fan. The advantage of a pump controlled this way is that it can be commanded to begin at a low speed or a fast speed, ON or OFF, etc., based on your custom programming and using a simple coolant temp sender (even a universal one) to maintain a certain coolant temperature. It can use a stand-alone controller or it can be connected to a programmable engine management system if that's what you have. This one is slightly larger than the first one above. About 4.6 x 3.2 inches and it weighs about 1 lb.. It's rated at 1000 liters per hour.  Bosch has a page for this: https://www.bosch-ibusiness.com/products/product-categories/auxiliary-pumps-and-valves/pce-039202453g/ Or they have a page listing several others: https://www.bosch-ibusiness.com/products/product-categories/auxiliary-pumps-and-valves/ If you're looking for pumps like this, you can search for Bosch electric cooling pumps (and be sure to choose 12 volts, because some are 24v). Or search non-Bosch and see what's out there. Sometimes these are listed as booster pumps or auxiliary pumps. This EBP is Bosch PN 039202343G. It's also brushless with a 3-pole connector. This one is smaller and lighter. About 3.5 x 3.5 inches and it weighs about 0.7 lb. It's rated at 500 liters per hour.  Bosch has a page for this at: https://www.bosch-ibusiness.com/products/product-categories/auxiliary-pumps-and-valves/pad2-039202343g/ More soon . . . |
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