2004 Alero Coolant Leaks
 

Dear OF users,
As seen from my name, this is research for my sweet old grannies 2004 Alero. (when we asked why she loves her Alero she replied that she is not a fast driver but she likes her car to MOVE when she presses the gas) And she is really not that old ~68 or so.

Either way, her Alero 3400 with 198,000 miles is over pressurizing the overflow coolant tank and sending antifreeze out the overflow hose.
In pursuit of the problem I have replaced the stat, replaced the over flow tank (it was mildly cracked) replaced the overflow tank cap, and performed a compression check (lowest 149-highest 163)
I cannot find the source of this tank over pressurization. The compression readings are sound for the engine's age, the tank and connections are solid, and I can see antifreeze running out the over flow tube.
Any help would be appreciated!
-Mahoney