Stuck thermostat causing pressure build up?

My car had recently had a pressure cap issue and I replaced it several time and had the water pump and timing belt done and any time I replace the cap it still just builds up pressure like the thermostat is stuck could this be something happening??

Other answer:

If you get heat at the center vents with in 5 minutes of driving I doubt you have a thermostat problem. How much pressure build up do you have? 16 lbs. of pressure is correct. If you are blowing out coolant like a geyser with the radiator cap off while parked you either have a coolant leak and air in the cooling system or a bad head gasket. If your temperature gauge fluctuates you have an air pocket in the motor.
David B:
Head gasket or cracked head.
Caps are suppose to build up pressure. That's why they have PSI ratings on them. The thermostat has nothing to do with it. Even if a thermostat was stuck closed, which hardly ever happens, the cap would keep the pressure at the right level.
Pilsner Man:
Head gasket. Have a pressure test done on the system. The aluminum cylinder head is the scourge of the earth. To save 20lbs, they went to an aluminum head on a cast iron block. Can you say dissimilar metals? Just WRONG!
thermostat can cause that, could also be an airlock stopping the thermostat from opening
Steve S:
head gasket leaking if its bubbling in the radiator consantly get the cooling system pressure tested will prove its leaking or not otherwise do a compression test

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