i have been have a problem with the cooling system on my car this weekend (civic eg D16Z6)

When i drive the car hard so that it starts to get hot, then the seperate header tank next to the radiator fills right up leaving not much left in the rad. This problem does not occur if i drive the car carefully.

I have bleed the system, but with the car running and the rad cap off i can see little bubbles every so offten not sure if this is part of the problem.

I think it may be a slight leak of the head gasket only when the engine gets hot, but im not sure. I have taken the oil cap off and then is no water in the oil.

Could it have some thing to do with the thermosat, as i have not replaced that in over 30,000 miles ( have been meaning to). this is my second engine in my civic and this one has always ran hotter than the than the other one.

What do you guys think the problem is????

 

has anyone got any ideas.

 

Sounds like a headgasket. Get a block tester or have a shop do a block test to see if the headgasket is blown. Go from there.