Originally posted by JEDsContour:
Do you have a V6? The 2.5L's are notorious for water pump deterioration. Relatively cheap and easy fix ââ?¬â?? if nothing else damaged.
Another more ominous possibility is cylinder leakage (exhaust) into the water jacket. This would be very bad news as it would indicate a bad head gasket (at best). Similar result to what you describe: coolant forced out of block under exhaust pressure into the radiator and overflow tank.
A compression test might reveal it.
Try replacing the waterpump first 
Ouch, don't scare me! 
You think water pump eh? Hmm... Coolant is getting forced back into the tank.
Hmm, I may try that. But there are no signs of water pump failure. Is this common?
Sal
SHOCal Advisor / Midwest Duratec Co-Owner
[img]http://www.supermotors.org/getfile/260278/original/CrackerBarrel.jpg[/img]
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