daschwa

Hello everyone. Just purchased a 1999 A6 2.8 Avant with 54K on it so I am a newbie around here. I have a feeling that the thermostat or thermostat gasket may not be functioning properly and was hoping for confirmation. When cruising down the highway, the coolant temp. needle sits at the first hash mark to the left of the dead-center 12:00 mark (hope this makes sense). Also, the needle tends to fluctuate: if in stop and go traffic, the needle will move to the 12:00 position but then when back on the highway it falls back to the hash mark left of the 12:00 mark. On my Passat, the coolant temp. needle sits directly on 12:00 once warmed up and does not budge so I am guessing the A6 should behave similarly. Also, assuming accuracy of the Oil temp guage, the Oil temp hovers around 175-180. I have searched the forums in hopes of an answer to my question but nothing concrete yet. So before I start throwing parts and G12 at the car does anyone have any suggestions? Thanks in advance.

charley_'99_A6Avant

175-180 is OK on the oil temp. The coolant temp should sit at the center position, left hash mark is a little cool. You may have a bad thermostat or a bad temp sensor. I would try the sensor first, its not an expensive item ($35-40). The problem here is getting the correct one. The parts dept may be able to get the correct one based on your vin number, but you may have to remove it and take it in to get the correct one.
Good luck. Charley

rrubya6

I have this same problem on my 98 2.8Q. I am sure it is the main thermostat (A6's have two) stuck open. Mine is due to go in to have it fixed in a couple of weeks. I'll let you know if my guess is right. I think if it was the sensor it would always read wrong and not go to the correct centre point wben the engine is running under heavy load or stationary.

Good luck

absolutcq20v

If it drops to a little left of center when cruising on the highway, I'd say thats normal. If it takes forever to warm up on the road (not sitting still), then you might have a t-stat stuck open. On the other end of the gauge, as long as it doesn't climb much past 12 noon (fan should kick on) you're also cool (ha, I crack me up!).

But, being only human and sorta green to the C5s, I could be wrong. :P