corsa

[knightrider]

overheating when ticking over

[Agent_Smith]

does your fan not work?

[almcd007]

Usually the thermo swtich on your radiator. By pass it and see if your fan works - if it does it's the switch.

[edd2blue]

might be air locking check see if right amount of water is in radiator!

[woodchopper]

Have had to change the thermostat on several of my Corsa's for the very same reason - you didn't say what year the car was so I assume it is pre 2002 which always had problems with them - the thermostat is located behind the timing belt which will have to be removed - if the car is due a timing belt change, get it done at the same time and if you are going to get the belt changed, make sure you get the Timing Belt Tensioner Pulley changed at the same time.
The cooling fan should kick in at about 96-99 degrees - if it isn't, get the thermoswitch replaced on the offside of the radiator.

Also check if there is water in the expansion bottle - if there isn't top it up and if, after you run it for a few days the water level goes down -barring any obvious leaks from pipes - get someone to check the head gasket hasn't blown - will usually manifest itself by the accumulation of white salts collecting at the point of the leak at the head gasket.

The head gasket was another one of the failngs on the Corsa's/Nova's/Astra's.