jyges

On the other. Audi board there are multiple posts of thermostat failures .Is it a real problem & what is cost to replace out of warranty.also do overheats due to stuck closed thermostats cause major engine damage as they due on my E39 BMW (1997-2003 ) 6 cylinders.

DrGP

They have been problematic. There was a recall and all the bad T Stats as well as water pumps should have been replaced under warranty. BUT, there still are occasional reports of 2nd T stat failures. The problem is that the Supercharger needs to be removed to get to the T stat. Don't think engine damage is common as long as you don't continue to drive and overheat the engine. The T stats seem to fail in the closed position

Timmay

Doesn't the T stat simply monitor the temps? I can't imagine it actually being the root cause of engine failure. As far as I know it's not regulating anything. I haven't had this issue with my new S4 of course but I did experience it with my '06 A3. Due to the transverse mounted engine it takes a crap load of time and labor just to get at it = $$$

gforaker

An engine thermostat regulates the flow of water through the engine and therefor the engine temperature. You are thinking temperature sensor, not thermostat.

Timmay

Ah you're right, thanks!