Hi everyone I'm new to this forum and looking for some help. I currently own a 06 PT cruiser and having trouble with the coolant flowing back to the overflow after the engine is shut off. I have replaced everything that has anything to do with the coolant. Radiator , fans, thermostat, thermostat housing, coolant sensor and even the water pump. I have vacuumed the system down to 26 inches of vacuum and also pressure tested the system up to 20 psi. all looked great. car does not over heat until several drives and the overflow tank blows coolant out and the system get low. I'm at a complete loss. PLEASE Help

 

Run a compression test to rule out a blown head gasket. Not likely, but possible.

 

You post of everything related to cooling system, and go on to list items. One not posted...how about a new CAP?

 

yeah sounds like coffee perking the cap is faulty