bernes1982

Please HELP
I just got a 2002 Audi A4 3.0 and the person who owned it before me recently had the timing belt, water pump and thermostat replaced. The shop that replaced the timing belt didn't do it correctly and the car was misfiring. I finally got that resolved. I just noticed that the car is overheating. When the car is moving everything is fine, but if I'm standing at a light the gauge starts to go up. As soon as the temperature gauge starts to go up I would take the cap off the overflow tank to remove some of the pressure, the temperature would go back to normal. Any suggestions??????????

lyleswk

Assuming you really do have a new pump and thermostat and the belt is spinning the water properly (based on the history I would be a little vervous here), then it is probably the fans. Are the fans coming on when it is overheating? If not, you probably have a bad fan control module or it is disconnected.

bernes1982

Yes, the fans do come on. When the car runs for about 5 min you can hear the fans turn on. After about 15min the tempereture gauge starts to go up. As soon as I remove the cap from the overflow tank and release the pressure the gauge goes back to normal. I've also noticed that when I release the pressure it feels like the coolant is boiling the the overflow tank.

ezveedub

You need to stop opening the coolant cap. You never open the cap on a hot engine, more so on an overheating engine. You're making the engine coolant boil over by releasing the pressure in the system and it will blow a head gasket or warp the heads eventually if you keep doing that. What you're probably seeing when you open the cap is the coolant vaporizing within the system and the temperature seems to go down, because the coolant sensor no longer has coolant around it when the cap is opened, so now if reads lower. But its actually hotter internally now because there's no coolant in the coolant jacket to cool the engine off properly as your releasing the pressure and letting coolant escape from the hot engine. You need to get the car to a qualified repair shop if you don't know how to diagnose this properly, as you're doing more harm than good.

lyleswk

I am with the comment on the cap; this is very dangerous. The reason is appears to work is a simple p=density*R*T thing, i.e., when you pop the cap, pressure goes down and then temp...at least temporarily.

My 2 cents: If the fans are coming on, you have a heat exchange problem which means the pump is not flowing properly, the thermostat is not operating, or the radiator is not exchanging heat. Since you say the pump and thermostat are presumeably new, then that leaves the radiator.