cupra cooling system pressurising up. help needed

[crack5111]

right. i recently changed the thermostat in my car as it took quite a while to get up to temperature and when it did it wouldnt keep constant.ever since i fitted the new one the cooling system has been pressurising up.so i decided to buy another one from seat as i thought the one i brought might not be opening or opening fully.ive fitted the genuine stat and its still the same. ive got water circulating through the top of the header tank but i dont know if its enough,its not overheating aswell so dont think its the water pump and its not using or loosing water.
what else could it be apart from headgasket?
could the secondary water pump cause any problems?

 

[tarzan]

might be some air in the system?

 

[crack5111]

i changed the radiator a while ago and never had anyproblems with air in the system and i would have thought it would have come out by now

 

[mini_hammy]

a thought pressure in the cooling system was one of two things either trapped air or head gasket failure???

 

[crack5111]

yer thats what i thought. think i'll just do a sniff test when i go into work and go from there

 

[mini_hammy]

ave never really heard of cupras with head gasket failure tho .... in my 7months of owning one haha