water pipe expansion

[tank_wrx]

hey all im hoping this is not what i think it is but ive bought my 1994 classic impreza a few day ago its had a new water pump this month and rad this month ive removed the thermostat today just to check if it was the problem or not

the problem or may be isnt is that the car warms up and when up to running temp the top house is hard not really solid but still a little hard and expands slightly the fan kicks in and back out again and gets no hotter my question is how hard should the pipe get and should it expand or is my head gasket on the way out ?

is any one about brighton burgess hill worthing area tonight i could compare with ??