Thermostat Madness

E-Twelve · Post by **E-Twelve** » Thu Jan 08, 2015 8:10 am

Hi.

I'm completely confused and hoping someone has an idea to help me. Currently my car never really gets to normal operating temp. The needle hovers around the first mark. It does this in the summer and winter. So I reckoned I need a new thermostat. I bought one from FCP, popped it in and take a test drive and it starts to overheat. I get back home, check for air in the system, yadda yadda, everything is fine. try again, still overheats. So I swapped the original t-stat back in so I can continue driving it. I figure that I got a bad new t-stat. So I ordered another one, this time a Behr. I get it, install it, and I have the same issue - overheating. So I swap back again. Being the idiot that I am, I bought one more new one - this time a Wahler (same brand as the original). It does the same thing.

SO I took all 4 of the thermostats to the kitchen, put them in water on the stove. They all, open, seemingly the same amount at pretty much the same temp, 80C. When I had them all side by side, I noticed that the original one, (the one that leaves the car running on the cool side) is shaped a little different. It is kind of "deep-dish" Where the 3 new ones I bought are kind of flat, the original has a lip that allows it to fit farther back into the engine.

What is the correct thermostat P/N? REALOEM has 11531251041 which is what I've been buying, but every one I get causes an overheat situation. I'm positive that I'm getting it bled correctly. Do I need a new housing too? What's going on here?

Thanks.

onovakind67 · Post by **onovakind67** » Thu Jan 08, 2015 8:42 am

What is your actual engine temperature?

E-Twelve · Post by **E-Twelve** » Thu Jan 08, 2015 8:46 am

onovakind67 wrote:What is your actual engine temperature?

I'm not sure. I don't have a thermometer. I can tell you that the cabin heat is poor - not nearly as warm as my other vehicles. So I believe the gauge is fairly accurate.

Doing more research, it appears that there are different versions of thermostat housings. I assume the thermostats I'm getting must be for the newest version. I need to verify which version I have I guess.

http://www.firstfives.org/bboard/viewtopic.php?t=2310

E-Twelve · Post by **E-Twelve** » Thu Jan 08, 2015 9:13 am

This thread seems to point out the issue. http://www.firstfives.org/wwwboard/messages/52302.html

I have 5 holes on my housing, so I have a new housing. If I look up pics of thermostats for the 1988 635CSI, then I see the type of thermostat that I have.

So I guess I'll give it one more try and buy one of those thermostats and see what happens.

Thanks.

Falkenberg · Post by **Falkenberg** » Thu Jan 08, 2015 9:34 am

I once had the old type thermostat in a newer M30, and it overheated.

wkohler · Post by **wkohler** » Sat Jan 10, 2015 9:13 pm

That should solve your problem. I put one that is too cold into my 530i, so if you want to divest yourself of one of those new older style t-stats, I'm your guy.