1.9 tdi 130bhp pressurisng

[Achie130]

Hi
Ive a 2002 130bhp avf passat

I bought it needing a headgasket

I stripped engine down head got checked new head gasked new head bolts. New oil cooler the water system got flushed a few times and oil and filter got changed.

The car is running perfect no powerloss great heater no over heating no mixing in the oil or coolant bottle but the car is pressurising any one any ideas???