I put my 2wd sapphire back to original 2wd header tank recently - it had a 4wd one when I bought it. Temp was fine before change. Now I am getting temp gauge going up near red when driving. It may drop back for a while and then back up. Cannot understand whats up with it - as its a simple change. I lost very little water from system when changing it over. Any help / advice appreciated.

 

Check you have not got a air lock.

Do your fans cut in?

it won't hurt to pull the stat housing out and check your thermostat.

run it to temp and feel around the radiator to see if it's the same temp all over.

If all is ok then pull the pump out and check to see if it's ok.

 

What is the best method to bleed air from system or avoid an air lock when refilling system?

 

patience.....

anyway, the return from the turbo should be the highest point in the engine, check you have water there, and when the engine is running if the water flows through.
I have seen on a peugeot 106 I once had that the temp was fine, but once i changed the water the thermostat got stuck afterwards

 

Cheers all - new thermostat ordered. See how she goes then.