p38 problems

Hi guys have a 95 4.0 v8 just done the head gaskets still have a problem with when the car runs for about 30 mins it pushes coolant up in the header tank top pipe does not seem to be pressurising and i have a powerful flow up through the throttle housing which returns to header tank like a fountain any ideas much appreciatted as is starting to fry my head.:doh::doh::doh::doh:,by the way when i had engine apart know sign of steam cleaned pistons etc , isuspect a coolant flow problem but where.

when you bleed them you need the heater full and on hot, you could still have a air lock..

only one side of heater will work and if i change to the other side it will blow warm and the other will go cold