Takeuchi TL 230 bubbling overflow tank

[jatspic05]

I have a takeuchi TL-230 with a kubota V3307 turbo engine. The coolant overflow tank is bubbling and flowing out the overflow tube. This happens on cold start and after running a while, so it is not boiling over. I have tested the radiator at the cap and pressure builds instantly to 30 psi. I have done a compression check and compression seems to be within spec 500,490,500,510 psi, I know there is a slight variance between compression readings, but not too extreme. The radiator cap has been replaced also. I am looking for some other possibilities before I remove the head and check the head gasket. I was considering the EGR cooler, but I believe the pressure builds too fast at the radiator inlet for the cooler to be the issue. Anyone have any ideas or could the head gasket be the problem?
Thanks

 

[mikebramel]

Easier to test the cooler than than the cylinder head.

 

[jatspic05]

Hi,
Tested the cooler and it was good. Sent the head out and had the surface checked and it failed. Also the piston bore was scored pretty bad, must have overheated and made contact with the bore. It was strange that the gasket didn't have any signs of failure. Oh well, just thought I would give an update.