Reviews of OEM Volkswagen thermostat

I had a bad thermostat and it's only indication was the temp rising when going up hills under sustained load.

I had this year ago, thermostat was stuck closed, so coolant couldnt go to big circle and into cooler, it went up after 10 minutes of highway driving up to 115° (obd temps) on dash it wasnt that much

I used the genuine part as there is no desire to redo it again too soon.

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.

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.

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.

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've got a 13 sport with 135k miles on it. Only ever done oil changes, spark plugs, 12v battery and a thermostat. Other than that it’s been stupid reliable.

Sounds like your water pump is working, but maybe your thermostat is stuck closed? Have you tested the thermostat?

mine is also a problem an my car is 1.5 yrs old. Sometimes the temp gauge acts as if it is -40C outside even if it is a couple degrees above freezing. Often the car will take 4-5minutes to get near base idle when it is cool outside, but when it's really cold, sometimes it takes 30seconds and there is no way it's warmed up. Can also smell coolant anytime I open the hood. Sad.