I have a 2002 A4 1.8 FWD with 78K. I have read some of the posts about the B6 overheating but would like to run my problem by the forum. I love this car and have had no real problems with it. Suddenly while driving up-hill, coolant light comes on and temp guage climbing to red. I stop and in a few minutes start her up and guage at 12oclock so I limp home stopping each time it starts to rise again. No coolant leaks, full resevoir, clear red coolant. Now when I start her up when cold, temp goes pretty quick to 12oclock and it can idle there without a problem. Top radiator hose, resevoir, gets hot and lower hose to thermostat stays cool. Turn on heater and I get hot air. After about 15min of idleing at this temp, I rev her up and temp begins to climb to 3/4, fan comes on and heater blowing much cooler air. Top radiator hose now really hot as is resevoir. Coolant warning comes on so I let her idle again and slowly the temp gets back to normal at 12oclock and heater blows hot air again. By this time the lower radiator hose and thermostat flange feels appropriately hot. I can repeat this by reving her again. I am afraid its the propeller on the pump slipping under load but just wondering if it could be a temp sensor or the thermostat itself? Much easier fix. Should I bother with the thermostat and is it possible with thermostat out that I can feel the pump blade for cracks? If it is the pump, is there a recommended timing belt kit that i should buy- pump with metal blades? New to this forum, ususlly spend time on Mercedes forum since that old car is much more trouble. Any help would be appreciated. I might just be in denial that its the pump but belt would have to be done anyway pretty soon.

thanks in advance,
Marc.

 

It sounds to me like you not getting sufficient circulation, so water pump could be the problem. But the thermostat could be partially closed, too.

At 78k miles you're due for the timing belt job, anyway. So replace all the goodies in there(water pump, t-stat, rollers, idlers) and make sure that you burp the cooling system properly when you're done.

Blauparts has a good kit, although you'd have to order the t-stat separately since this kit does not include it.