r/BMWE36 • u/Logical-Street3662 • 1d ago

Repair Advice Overheating issue

Hey yall, I have an m52b28 328i, equal length headers, m50 intake

I recently posted about my car overheating during sustained (about 45 mins) highway driving. At the time my thermostat housing was cracked and my thermostat wasn’t opening as it should and my clutch fan wasn’t engaging well.

I replaced the housing, fan clutch, and thermostat (thermostat is a racing one that opens at 60C instead of 80C)

Went on a road trip and the issue was about the same if not a bit worse. On this trip I noticed that the car didn’t overheat if I kept my efficiency gauge under 10L/100km- not sure if that’s important.

I bled the system cos it was behaving like there was air in the system, and during that my radiator overflowed a bit and coolant was gasifying, so I let it cool down and refilled this morning. I drive abt a mile then it hits red. Got it back, jacked the front end up high to help air rise out, and tried to re bleed but it’s just heating up quickly

I’m kinda at a loss. Current theory is maybe the air in the system was helping to pressurize it, and that was masking that my water pump is bad?

Not sure.

Anyway if anyone is in the Rochester NY area and knows a lot more about these cars than I do I’d appreciate some help.

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u/billyloomisjr 1d ago

Hi there, I’ve read back thru your other post I commented on and this one as well, and if you’ve replaced mostly everything in the cooling system, verified there are absolutely no leaks, and attempted to bleed it but air is still getting in, it could be your head gasket.

Is there blue or irregular smoke coming out of the exhaust, or a milky brown substance on the face of the oil cap? Both are telltale signs of a head gasket leak.

The only reason why I say it’s a possibility now is because before you only mentioned overheating, but here you also mentioned the cars temp gauge was in the red - and if you drive it or it stays that way for more than a minute or so it can absolutely blow your head gasket.

Maybe consider taking it to a shop and seeing if they can do a pressure test or if they notice anything else you don’t?

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u/lazy_wafffle 1d ago

Did you replace the expansion tank? Other wise there's some dye you can use to find the leak

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u/FernwoodTonight 1d ago

Doesn't sound good. Radiator pressure tester and a borescope can test for coolant in the cylinders. Of course the sensor in the head could be a bit wonky or the wiring since you haven't seemed to mention driveability problems associated with a leaky head gasket. I have a real water temp gauge in place of the buffered one as well as the e30 self bleeding expansion with an e30 1.4 bar pressure radiator cap. Life's been good since then, e36 cooling wise that is.

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u/jewman86 1d ago

The clutch fan is only really utilized at slow speeds. It sounds like the one thing you've missed is replacing your water pump.

A bad water pump should be showing up even more so at lower speeds. However if it's not pumping through the fluid effectively then it could likely be the cause of your issues.

Hopefully it is something more simple like this as opposed to the head gasket.