Thermostat OEM BMW or OEM Volkswagen

My 535i with the 740d thermostat sits at 90-95 during normal use, even sat stable at 95c during 40c weather in traffic. When beating on it in the mountains got it up to 99 at like 28c ambient.

I have this exact engine and installed a diesel thermostat. Previously, with the standard thermostat, the plastic timing chain guides would start to disintegrate after three years, but now I have no problem with that. The engine temperature is around 96°C.

It has been two weeks since the repair without issues, so I am going to call this one solved. If I was paying for this out of pocket in the future, I would only replace the thermostat and not the pump as that is what was closing and causing the issue.

Thermostat is an bmw part so its fine

I did the timing belt water pump thing on my MK4 last year, and shortly after the test drive with fresh genuine VW antifreeze and while patting myself on the back for a job well done it occurred to me that I hadn't changed the thermostat. Sure enough a month or so ago when the first of the really cold whether started around here the temp gauge would only get to about halfway to normal during a trip to town and back. I tried the ol' cardboard in the grill routine for a couple of days until I got a chance to change the thermostat and that brought things back to normal.

Parts 03F-010-501-B Sensor 04E-121-113-G

I have owned my B6 since new and had the thermostat replaced under Warranty around 36,000 miles, at that point the slow warm up was causing the MIL to illuminate with a error that basically said warm up outside specification.

Original was stuck open, replaced with new VW which now appears to be stuck closed. ????. Fortunately I have recently acquired a new OE thermostat on clearance for jollies.

After getting mine back together, and filling it back up with coolant, i found the new thermostat from the dealership was stuck wide open and the car wouldn’t get over 110*F.

I replaced the t-stat with a genuine part and again no luck.