Hey, I recently had a head gasket done on my s2 escort rust turbo. It was boiling up previously as the gasket was blown into the cylinder/water jacket and a test determined that gasses were escaping into the coolant system. However I have had the gasket changed and the water is still bubbling furiously in the expansion tank. I have noticed the expansion tank has cracked on the rim half way around the cap. Is this likely to be why the water is going crazy? It doesnt do it immediately, has to be driven around for a bit. I have a new expansion tank arriving tomorrow, but if anyone can answer my question it would be great. Would running too little boost be a cause of this as I turned it down on the actuator to 9psi due to the gasket being fooked. Usually its around 11-13 psi. ta.