Overheating

["David Sims" <gcj72@domain.elided>]

I received the following query via email and would like to invoke the
collective wisdom:

TIA


My stag has always behaved itself when it came to the cooling system NEVER
moving passed the Normal position.
One day My RAD leaked, the car almost overheated but didn't !

I go the RAD rebuilt,,

Now ever since then the temp always goes very high and indeed eventually My
Head warped !!!

I have just skimmed the head and rebuilt the engine ...

BUT it is still running hot ,,,

The Odd thing about it all is , if I have the Heater on HOT the temp is
perfect !!!!!!

When I put the heater on Cold it starts to run Hot, and will eventually
overheat ...

For some reason I don't think water is circulated properly around the
radiator, But when I put the heater on hot, the heater seems
to be taking the prominent role in cooling the car down ...

Do you think this could be the Radiator being faulty or the Water Pump being
inefficient ?

Any ideas,