I am goint to post the full picture just incase there is any relevance. Last December I needed to have the altenator replaced in the car for obvious reasons, now the car has hardly been run but developed overheating problems three months ago. I took it to the same garage that I have been a customer with for at least 7 years and do trust them. So it was advised that it was the water pump and that the viscos fan had completley died, so these were replaced I was advised that the thermostat was ok. Two weeks later the same thing happened just in time for its MOT, the system was re bleed and passed its MOT with a few advisories. Now the story unfolds since then on cold start up the machine rattles like a Harley Davidson from the drivers side of the engine and there is a tapping noise also, this usually settles down once the engine is up to temp, however over fifteen miles the machine overheats to the first part of the needle just before the red. Usually putting on the blower at full brings it back down, however not latley. Now there is ocassions that the car does not have any of these symptoms and drives as it should do which is quite unreal.
Another factor is that when removing the cap from the expansion tank it takes at least 10 to 15 mins whilst it releases a lot of preasure and gurgling hissing noises like back preasure. I have checked the oil for evidence of water in it as I have been advised suspect overhead gasket I see just normal oil and the coolent seems to be clean as well, I am scratching my head as much as the mechanic, I do hope that somebody on here can throw some light on this. The machine has done around 70 thousand miles, and I myself only do around 6 thousand a year always serviced and looked after help please