love this little car but have been plagued with heater and water problems, finally had mobile mechanic to put a new ford hcv on the car but on testing, the coolant blew from the expantion tank, so new tank, and cap, we thought cylinder head had gone, but no messy stuff, and he did a sniff test and that was ok, soooo any ideas,hubby wants to get rid but I love the car, but is there some thing we are missing, I have trailed all the sites looking for advise, but I think we need a bit  by bit walk through of what to do, if you know what I mean , oh and if the sniff test said the cylinder head is ok can we believe it, sorry if this post is a bit mixed up .

Unclear what the problem is . You say HCV replaced along with tank and cap and that head gasket test OK. Are you say it is still blowing water through the cap?  Is this only when it gets very hot?  is radiator fan kicking in?  what is temp guage saying (I don't actually know if it has guage or not).  

A friend had a car which was overheating and breakdown service said head gasket gone but it was in fact the radiator fan not kicking in because the fuse had blown. Luckily not lasting damage once fan sorted out

Hi Thanks for the reply, the fan is kicking in,it does blow the cap when it is really hot,the only thing we have not changed is the water pump, but the water is circulating radiator is getting hot so are all the pipes and as my hubby says thats it he cant think of any thing else 

Could be the thermostat stuck shut.

in addition to the above, I have known radiators to get silted up and restrict water flow.  Years ago (eg. a Cortina radiator which had a hose connection at the top and the bottom - the tank parts were at top and bottom, not on left and right like modern ones) I think  you would take it out of the car turn it upside down and use a hosepipe to reverse flow water through it to wash the silt out.  I don't know if this happens on modern cars