discovery overheating

hi new to this site and just bought myself a new discovery (1995 300 tdi) and it drives fine on long or short journeys if the heater knobs are on hot with fans off..... but if i turn them to cold still with fans off the tempreture rise's very slowly until almost in the red but if i turn heater knobs to hot again it will go back slowly to halfway and stay there until you move heater knobs to cold again does anyone know of this problem and any known fixes thanks chris.

Hi m8 my 200tdi only goes to 1 1/4 of the guage could be the head gasket is on way out wots it pull like

It sounds like you have a coolant issue with the radiator, the fact that putting the heater on hot allows it to run at an OK temp sounds like the heater matrix is compensating just enough for a blockage etc in the radiator.

Does it have enough coolant? is it using any coolant?

If its not using coolant, then I would; for the sake of an hour and 5quid worth of antifreeze drain the system and flush it out, stick a hose through the rad until it runs clear and the engine and heater matrix - you will need to undo a few pipes throughout the system to flush it.

Make sure the radiator runs freely, if not fill it from the bottom hose and see if you can lift out any gunge.

True it could be a head gasket issue, BUT you say it does run fine with the heater in the hot position (this opens the water flow up to the matrix) so it sounds more like a cooling system issue.

hi as for power she pulls fine without any effort and as for coolant no signs of water loss anywhere and the level is spot on so going to try flushing the cooloing system as you mention and see how she go's thanks chris.

Check the thermostat also. Same thing happens when it doesn't fully open.

cipx2 said:

Check the thermostat also. Same thing happens when it doesn't fully open.

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YES indeed, I managed to neglect to mention that one!

flushed cooling system and changed thermostat and it seems to of cured it no overheating!! so thanks to all who helped