The car is 1993 100cs quattro, 2.8 v6 auto air. The temperature gauge does not rise up to the same position as it used to. In fact it barely moves at all. There is moderate heat coming from the defroster. Its actually just warm air than anything else. Also the oil temperature gauge barely rises. With the engine running this cool it does not burn the fuel properly and then my check engine light comes on. I suspect the thermostat but from what I've read in this forum it sound like its just blocked with dirt. The rad was flushed about three years ago and then filled with the blue audi coolant. From what I understand the thermostat is behind the timing cover. Do I need to flush the cooling system again or replace the whole thermostat? P.S. Keep watching this space as this car may come up for sale for parts.

 

i think i would be inclined to change the thermostat (as it is a 17 year old car anyway) as well as try a coolant flush. more than anything, this sounds like a t-stat issue to me.