Anyone have any experience with the Wahler thermostat? I ordered this thermostat as an "OEM" thermostat, but it seems there are differences between this one and the one that came out of my MINI. Here's the story:

Recently our Cooper S started running hot, especially when coming off the highway or in traffic. I checked the coolant level, and sure enough it was low. Topped it up and all was fine. A week later, same thing. Apparently we had a slow leak. Searching the forum I found that the thermostat housing is a common culprit of leaks. So in addition to the new thermostat, I also ordered a new housing and gasket. I just pulled out the old one today and found that the OEM thermostat is not EXACTLY like the Wahler. So I decided to conduct an experiment.

(As a side note, my other car is an Audi TT, and the Wahler thermostats for the TT are proven to not open at the same rate and temperature as the OEM. Therefore it is recommended to stick with the OEM thermostat as purchased from the dealership when replacing. Hence my suspicion of this one.)

I heated them both up in a pan of water. As the temperture approached 200F, both thermostats started to open (as they should - at 195F). However, I noticed that the Wahler actually opened WIDER than the OEM. In fact, the OEM barely opened at all! I can see this being a big problem with overheating.

Here are a few pics. Wahler on the left, OEM on the right. Note how much wider the Wahler has opened.



Close-up:


Out of the water:



So my question is: Has anyone installed a Wahler thermostat and has it caused any issues? In my situation, it seems like it could only help the engine to run cooler, not the other way around (as I experienced with my Audi). Maybe my overheating was caused more by the OEM thermostat failing to open rather than the low coolant situation. However, after I topped up the coolant, the temp remained normal until the coolant level dropped again.

Furthermore, I have never seen a thermostat fail in the CLOSED position. AFAIK, I thought they were designed to fail in the open position so as to avoid a potentially dangerous overheating situation.

 

looks like the Wahler opens further which seems good.

I thought thermostats failing in the closed position. On every car I owned that had a thermostat failed, it resulted in a dangerous overheating situation.

 

Yeah, standard design uses the melting wax to force the 'stat open against
spring pressure. Spring forces closure as wax resolidifies. Failure=overheating usually. Some failures (piston jamming) will leave 'stat open.

 

Where do you buy non-oem thermo stats? I had a leak that would come and go. I read through these threads and deduced it was probably the thermostat. It gave me an excuse to replace hoses with silicone and replace the overflow tank too. Well I didn't feel like paying the $40 at dealership. I bought one at Napa and the design was different (it is missing the notches around the outside and no gasket) I went to pepboys and autozone and they both had the same style with no gasket. The problem ended up being one of the bolts on the housing was loose. If it comes to me replacing the thermostat/gasket where can I get one besides dealer

 

I got mine from BimmerSpecialist.com.

http://www.bimmerspecialist.com/usa/

Part number 11531485847. About 32 bucks for the thermostat with gasket. The site says "OEM" but clearly it was not the same thermostat that came out of my MINI. I also bought the thermostat housing from the same place, also about 32 bucks.

 

thanks

 

http://www.realoem.com/bmw/showparts.do?model=RF32&mospid=48015&btnr=11_3099& hg=11&fg=35
Mini Used 2 different termostats:
Thermostat with gasket p/n 11531485847
Thermostat with gasket p/n 11537596787

Maybe this is why they are different.
Also probably they changed it to fix issue.