as the topic sugests i got an air block in my cooling system, ive tryed bleeding the air out, runing it with the cap open. ive already put 3 different thermostats in it and it seems to have the same problem. you can feel air in the top radiator hose when hot. when the car is driven for a while and stopped you can hear a thumping noise coming from the thermostat lasting 4-5 seconds and then bubbeling inside the top hose. apart from that the car dosent overheat and reaches normal opperating temp fairly well never gets past 95 degrees. any sugestions how to get rid of air from the system or what the noise is??

sorry about the long post.
thanks guys

You say you've bled the system so there shouldn't be any air in there.

What happens after a reasonable drive, the engine reaches operating temp and is close to boiling point. You then switch off the engine, and say that the ambiant temp is quite warm. The engine will heat soak, due to no longer having coolant flow (water pump not turning) and no longer having any airflow through the radiator (cooling fans switched off).The under bonnet temp will then rise (some times upto 20 degrees) This may allow the coolant temp to rise to a point where it may boil and cause that thumping noise in your top hose.

I've noticed my EL ghia has done this once or twice usually pulling upto a servo after at least an hours drive on a warm day.

After you turn off the engine, turn on the ignition, you'll prob be able to watch the temp gauge rising.

when filling the system do you remove the small hose from the thermostat housing to release the air?

That hose leads back to the top of the reservoir and its job is to return all air to the reservoir tank. So as long as the cap is off when warming engine to remove any air, all the air should return to the tank.
I have heard a small hole in the body of the thermostat will help any air in system move passed the thermostat and back to the reservoir

Most thermostats these days already have that hole in them to bleed the system.

It could be your radiator cap is stuffed and not keeping the system properly pressurised.

yep i did undo the small hose and made sure coolant flowed out of the outlet. i got a new thermostst and drilled a 5mm hole in it and made a little brass bleeder to fit it and bled the system again it seems to have stopped but for how long?? i'll just have to wait and see.
thanks for the replys.