I've found conflicting information on a few things regarding oil filter housings and what will bolt onto an M50. I believe the euro oil filter housing is a *definately fits*, but I've heard of others potentially having fittings on the back for coolers that are not the euro one. S54 housings are supposed to be the same as the euro housing? or is it just the early S54 housings? any others?

On the euro/S54 oil filter housing, is the oil cooler output regulated via a thermostat? Or just a full flow in/out?

Most seem to run plain coolers. Why not the use of heat exchangers using the coolant system?

Or just a full flow in/out?

Yup. If you use the Euro housing, be sure to get an adapter that changes it to accept AN fittings. At least that's my preference over the stock hardlines.

Most seem to run plain coolers. Why not the use of heat exchangers using the coolant system?

Because it's easier this way?

I've found conflicting information on a few things regarding oil filter housings and what will bolt onto an M50. I believe the euro oil filter housing is a *definately fits*, but I've heard of others potentially having fittings on the back for coolers that are not the euro one. S54 housings are supposed to be the same as the euro housing? or is it just the early S54 housings? any others?

Early S54 filter housing has the same part number as the S50B32 housing.
ETKA can verify.


On the euro/S54 oil filter housing, is the oil cooler output regulated via a thermostat? Or just a full flow in/out?

Built in t-stat, opens ~180* F, IIRC.

Built in t-stat, opens ~180* F, IIRC.

Strange. I could have sworn that ours was open all the time. Perhaps it's modified and I don't know about it. Where is the T-stat located in the housing?

RealOEM.com shows a temperature switch, but I was under the impression that it was just a sensor and not a thermostat:
http://www.realoem.com/bmw/showparts.do?model=BG91&mospid=47433&btnr=11_1302&hg=11&fg=30

Most seem to run plain coolers. Why not the use of heat exchangers using the coolant system?

Used them before and it caused the car to overheat during long on track sessions. Oil temp and water temp was welll above 200 degrees and would not come down.

Used them before and it caused the car to overheat during long on track sessions. Oil temp and water temp was welll above 200 degrees and would not come down.

Just wondering...so when you guys race, do you usually aim for less than 200 for oil and water?

Just wondering...so when you guys race, do you usually aim for less than 200 for oil and water?

Pretty hard to kee water below 200. On my 95 M3, it idles at 210, and get to about 215-220 on all out sessions. Not sure if the s54 is different.

Pretty hard to kee water below 200. On my 95 M3, it idles at 210, and get to about 215-220 on all out sessions. Not sure if the s54 is different.

Thanks for the insight.

I posted this elsewhere and didn't get an answer. So does "overheating" refers to the needle starting to move from its transient position but never touches the red zone, or the needle getting in the red zone? I have spoken to some folks and they refer to the latter.

Just wondering...so when you guys race, do you usually aim for less than 200 for oil and water?

I dont see how oil could stay below 200. I saw 280 at Summit in August (90+ heat) for the 60min enduro and around 230 water temp when we were under full yellow. My temp sensor is tapped into the pan so the readings are always higher.

Thanks for the insight.

I posted this elsewhere and didn't get an answer. So does "overheating" refers to the needle starting to move from its transient position but never touches the red zone, or the needle getting in the red zone? I have spoken to some folks and they refer to the latter.

I have no idea on a stock gauge. Use a good aftermarket one. The OE is basically an on/off light (stolen from another thread). To me, overheating is when the water is all over your windshield :)

Used them before and it caused the car to overheat during long on track sessions. Oil temp and water temp was welll above 200 degrees and would not come down.
Not enough radiator to compensate for the added thermal energy being dumped into the water based cooling system?

Which radiator was used and was it changed when the heat exchanger was added?

How large of an oil cooler is used now?

I've asked before, but I'll check again to see if I'm remembering correctly. What are the usual target water and oil temps for "stock" to "stock-ish" M50 based motors? ~200 for water and ~230 for oil? Measured where?

thanks :)

I dont see how oil could stay below 200. I saw 280 at Summit in August (90+ heat) for the 60min enduro and around 230 water temp when we were under full yellow. My temp sensor is tapped into the pan so the readings are always higher.

My point exactly...

which is why I asked Seth why he implied temps to be below 200.

I have no idea on a stock gauge. Use a good aftermarket one. The OE is basically an on/off light (stolen from another thread). To me, overheating is when the water is all over your windshield :)

Now that is definitely overheating! :D

One thing the Radiator based cooling is good for is the car warms up faster....not that it's a huge advantage. Just thought I would interject that.

I've always heard you want hot oil and cool water temps for race motors (IIRC).

Everyone should be using straight race oil, not multi-vis, in their track cars. Red Line 40WT Race Oil seems to be well suited for higher oil temps, and 50WT can be used in very hot climates (basically any track in the summer).

Michael is right, the cooling system capacity must be increased when using a water/oil heat exchanger. I know PTG used (still uses?) them, I'm sure at least in part to prevent rock damage from taking out their oil coolers during endurance races. Their radiators for the S50s were huge, too.

Oil temps tend to climb when water temps inch up even slightly, so making sure you have enough radiator for your outside temp and power output is important. Additionally, many racers don't see the need to keep the proper ducting to the radiator, which allows the air to spill around the exchanger rather than run through it.

The S50B30/B32 Euro housings are in fact the same as the S54 (M Roadster and 2-door included), part number 11 42 1 404 206. There is a wax thermostat inside that controls the temp, and it can be removed for you to use an aftermarket thermostat. There are large plugs on the back of all the other M50 housings, but those may be there for machining purposes, then sealed off. I've never torn one down to check, but I have a couple lying around.

Our 330i Grand Am Cup car will routinely run 160-180 F water temps & 230-260 F oil temps at full-race pace in 90 F weather, with an external oil cooler. No problemo.

But also remember that you're not putting out as much power as the heavily modded motors, AND you have an aluminum block which further helps shed heat.

I've used a radiator with built in heat exchanger successfully, but only on the drysumped version of my engine.

As soon as I removed the dry sump system, it did not cool oil sufficiently.

The dry sump system was based on a thermostat deleted and modified oil filter manifold. The take home lesson is that if you also have about 35 feet of various diameter SS lines of aeroquip line that is exposed and radiating heat, AND the oil is stored in a tank that is not heated by the engine, you may be able to get away with some brands of heat exchangers that are built into the radiator.

However, i can not state with authority that there may not be one that works for non dry sumped engines...it just didn't work for me.

Now I have a super large, bigger than need be radiator with heavy heat exchanger built in, and unused at this point. Back to stock thermostat set up that is built into the oil filter manifold. Great, just what I need, more weight in the front of my car. A simple Earls oil cooler is now parked in front, and works well.

Simply tapping the outputs of the euro housing may require use of adaptors that will decrease the diameter of the oil lines at that point. Watch and be careful. You can have a professional hose shop swedge on fittings to the factory lines, and go to AN 12 nicely, and build whatever hoses you want from that point on.

If you're overhauling your oil system, take the time to put in a 30 or 40 psi idiot light, and a real oil pressure guage. I've posted extensively on this in other locations, and included the rational there.

Alex Lipowich

Our 330i Grand Am Cup car will routinely run 160-180 F water temps & 230-260 F oil temps at full-race pace in 90 F weather, with an external oil cooler. No problemo.

Where is your oil temp sender located? In my wet sump motor, mine was in the pan and we regularly saw 300 degree oil temps on a relatively stock S54. I am dry sumping the motor as we speak and will let you all know the results.

Where is your oil temp sender located? In my wet sump motor, mine was in the pan and we regularly saw 300 degree oil temps on a relatively stock S54. I am dry sumping the motor as we speak and will let you all know the results.


IIRC, it is in or near the filter housing. I can check & verify, if it would help you out. Please let me know.

James, you are correct. However, I am frankly not sure how much heat is actually shed by the block as a total % of heat produced. Instinct says not a lot, given the confines of a stock closed, unvented engine compartment. In addition, I would suspect that even our low powered lump produces equivalent BTU's on a 90 degree day in a 2.5 to 3 hour race!!

Not enough radiator to compensate for the added thermal energy being dumped into the water based cooling system?

Possible but it was a bigger radiator than stock.

Which radiator was used and was it changed when the heat exchanger was added?

C&R racing radiator custom built to fit E46 3series, was built with the heat exchanger, and built with the exchanger being considered in the equation.


How large of an oil cooler is used now?

Not sure


I've asked before, but I'll check again to see if I'm remembering correctly. What are the usual target water and oil temps for "stock" to "stock-ish" M50 based motors? ~200 for water and ~230 for oil? Measured where?

Usually we shoot for around 180 water and 220 oil in the World Challenge cars.

Wonderful info. Thanks Seth, James, and everyone else in this thread. :)

I'm suprised to see target temps so low.

Where is water temp usually measured? In the head itself, or coming out of the thermostat housing (upper radiator hose)?

Are most running the thermostat in the stock location? Post engine? (it's in the same general location on the S54 and euro motors as it is for the M50, correct?)

I was quite comfortable with where my oil and water temps were, but am starting to reconsider my target temps. Peak water temp was just over 210 for me, and peak oil temp was 250. Water temp measured in the upper radiator hose and oil temp measured at the oil filter housing.

I'm still not keen on the thermostat location. I don't know of anyone that has bothered to move it though, so perhaps its not all bad. :dunno

Wonderful info. Thanks Seth, James, and everyone else in this thread. :)

I'm suprised to see target temps so low.

Where is water temp usually measured? In the head itself, or coming out of the thermostat housing (upper radiator hose)?


Likewise ... I have my water temp sender tapped into the thrermo housing, just past where the upper rad hose comes in. I see 220º on occasion. I'm only running the electric fan, though I don't think this is an issue at speed.

Hello Mike.

I thought the water output of the motor was the lower radiator hose. Did someone confirm your thought that it was the top one? My mechanical oil temp sensor is tapped into the sump and I see 260 regularly during the summer. I have seen 270 once or twice during 30 minute sessions on 95 degree days on my former non-vanos M50. Mobil1 15w-50 is what I use. Mobil literature states that their oil is good to over 300 degrees. Not that I would ever run it over 300. My mechanical sensor on the lower hose has gotten as high as 230. It normally runs 215-220 during 25 minute instructor run groups in 90+ degree weather. The only time it runs higher is at VIR south course where there is only one long straight to cool down on. This is with a fan delete and lower temp elec fan switch.

I'm pretty sure of the flow direction. Upper is the outlet from the motor. The lower hose is on the cold side of the radiator, which is why the fan switch is also on that side.

Also, the lower hose is always colder than the upper hose.

Stop trying to confuse me. :stickoutt ;)

I'm pretty sure of the flow direction. Upper is the outlet from the motor. The lower hose is on the cold side of the radiator, which is why the fan switch is also on that side.

Also, the lower hose is always colder than the upper hose.
That is correct. If you're seeing 230F at the exit of the radiator (on M50, it is the right side hose from the lower outlet on the radiator), that's really high.

The coolant system is designed as two loops. The first loop is water pump to block to head to outlet (usually the thermostat housing), back to water pump. The second loop opens up with the thermostat, and it then runs water pump to block to head to thermostat housing to upper radiator hose to lower radiator hose, back to water pump. Even with the thermostat blown wide open, some water from the head (hot) goes directly back into the block.

The preferred place to measure water temp is either in the head near the front (M50 style) or at the exit of the head but before the thermostat (S14, S38, Euro S50, etc). Putting the temp sender in the upper rad hose can give erroneous radings if the thermostat is malfunctioning. Worst case is if the thermostat fails shut and never opens, the upper hose will not get any hot water, and it will read falsely low.

With the thermostat not blocking flow to the upper radiator hose, the upper radiator hose will still see temperatures similar to the outlet side of the thermostat housing as there is no thermostat completely blocking flow there. It won't be pump based flow, but still enough to get a very similar reading in the first 8 inches or so of pipe as compared to in the outlet side of the thermostat housing itself.

With the thermostat open, the readings in those two locations should be the same.

Ideally, the sensor would be in the head near the outlet. (such as where the stock temp sensors for the DME and temp gauge are located). Not being fesible for some, the thermostat housing becomes a common location to be drilled and tapped. I'm not a huge fan of drilling and tapping such thin pieces of cast aluminum. I'm also not a fan of putting a brass NPT fitting in very thin aluminum. With tapered threads and thin cast pieces, it only takes one overzealous monkey to twist it a 1/4 turn too far. ;)

The thermostat being on the inlet side of the motor makes for some interesting temperature variations on different segments of a track. The low load (even at high RPM) segments are a decent bit cooler than the high load sections. Likely a result of stabilizing the inlet temperature instead of regulating based on outlet temperature. I'm actually rather suprised it hasn't become a problem for anyone.

With the thermostat not blocking flow to the upper radiator hose, the upper radiator hose will still see temperatures similar to the outlet side of the thermostat housing as there is no thermostat completely blocking flow there. It won't be pump based flow, but still enough to get a very similar reading in the first 8 inches or so of pipe as compared to in the outlet side of the thermostat housing itself.

With the thermostat open, the readings in those two locations should be the same.
Yep, that's true. It's only if the thermostat fails in the fully closed position should you be worried. Most of the time (from what I've heard) the thermostat fails either partially open or physically breaks and allows coolant to flow unregulated.

...the thermostat housing becomes a common location to be drilled and tapped. I'm not a huge fan of drilling and tapping such thin pieces of cast aluminum. I'm also not a fan of putting a brass NPT fitting in very thin aluminum. With tapered threads and thin cast pieces, it only takes one overzealous monkey to twist it a 1/4 turn too far. ;)
Yep, it is much better to properly weld in a threaded bung. I've seen a couple tapped housings that never sealed properly and were gooped to prevent leaking around the threads.

Thanks for the responses James. :D

Yep, it is much better to properly weld in a threaded bung. I've seen a couple tapped housings that never sealed properly and were gooped to prevent leaking around the threads.
welding in a threaded bung would likely involve things like removing the head. :stickoutt
My 2.5L motor has never been opened. Stock head gasket, stock head bolts, etc... maybe one day it will get the proper treatment though.

welding in a threaded bung would likely involve things like removing the head. :stickoutt
My 2.5L motor has never been opened. Stock head gasket, stock head bolts, etc... maybe one day it will get the proper treatment though.
Oh, no, I meant welding a bung in the thermostat housing. Welding on the head is not really necessary. The M50 head has 3 holes in the coolant jacket under the intake manifold. The blue sensor goes to the DME, the black one goes to the gauge, and the nipple goes to the throttle body heater (for cold weather driving). They are all M12x1.5 thread. If you want to put a sensor in the head, use one of those holes.

The M52 head has 2 holes. The third hole was never drilled and tapped from the factory, but is an easy job once the intake manifold is off.

Where is your oil temp sender located? In my wet sump motor, mine was in the pan and we regularly saw 300 degree oil temps on a relatively stock S54. I am dry sumping the motor as we speak and will let you all know the results.

I have my pan off my m3, and I wanted to drill and tap the thing with it on the bench... I want to know where on the pan the best place to drill for the sending unit is?

I would guess somewhere on the drivers side away from the exhaust manifold somwhere close to the pickup???? just thinking the residual heat may alter readings!?!?!?

'tanks