Help.. my 2010 Vauxhall Mariva is over heating every other day

Hi all...

please please help, my 2010 Mariva keeps over heating every other day..i have changed the Temperature gage, the thermostat, and the water pump.
It still happens. I have turned the engine on and let run with the heater of full, and left the expansion tack cap of, once at 90% I squeezed the pipes to get any air out.

There is no white muck around the oil cap so the head gasket is fine.

However, it only happens now and again, I can drive it for an hour down the motorway and its fine, then I can drive it for half hour and it goes up to about 110% when I slow down or stop. Once I start driving again, it starts to go back down. The only thing I haven’t changed it the expansion tank cap, however this looks fine and the rubber washer is in tacked.

 

Only if it's not leaking on the oil side. Get a block tester see if any exhaust gases present in the cooling system that would let you know if head gasket is ok or not