pghs4

Hello all,

My '00 S4 has been overheating the past two weeks. The coolant gauge needle jumps past the middle after the car warms up. Sometimes it will move beyond one tick past the middle after highway driving. All fans seem to be functioning normally. I replaced the green temp sensor, but nothing has changed. The only way I can keep the car from overheating more is by running the heater on high. The timing belt/water pump/thermostat were changed 30k miles ago.

After looking at the radiator, it seems the left side (drivers side) is very hot but the right side is only warm. That tells me it is either the thermostat or the radiator is clogged. How can I determine if the radiator is obstructed? Would the heater still work if the thermostst is stuck closed? It throws pleanty of heat. Any help would be greatly appreciated. I would like to avoid having to do another timing belt right now if at all possible. Thanks.

Tom B.
'00 S4

Peter Badore

Yes the heater works with the thermostat closed as during warmup or if the thermostat is malfunctioning heater works. Are you sure the fan clutch
hasn't worn out? The clutch should not spin freely by hand? Is the coolant G12?
I have repaired two Audis recently with clogged radiators and sludged cooling systems when the incorrect coolant was used in them.

pghs4

Just to follow up, I performed a timing belt job and replaced the thermostat a couple of weeks ago. The car no longer overheats! Just as a test, I put the old thermostat in a pot of boiling water, it did not open. It seems the plate that is to open and close is seized on the shaft. How does this happen? The thermostat has only 30k miles on it and is only about 3 years old. The coolant was very clean. No visible corrosion on the thermostat. Just my luck, I guess. Thanks for the help!

Tom