Quote Originally Posted by GazC
It sort of worked but only luke warm air but the water pump was basically goosed so thought replacing that and a system flush would do the trick. Didn't change the Thermostat as thought it would be ok...would it be stuck open?

Edit:it's an M44 engine and I didn't physically remove the thermo to test it no. Could that be the fault. Checked the coolant levels again this morning and it barely moved so don't think there is any more air trapped.

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It sounds like either an airlock or the stat is stuck open. If you can take out the housing with the stat, you could try drop it in boiling water to see if the bi-metal strip causes it to move, if it's broken it will stick open as that's the design, they fail open. If it were to fail closed as in stuck shut, the engine would overheat fairly quick and blow the head-gasket. It fails open to allow the coolant to circulate. However the engine will eventually overheat this way too.

If there is an airlock, one side of the hosing at the rad would be hard; as in pressure in it, and the hose on the other side of rad, you will be able to squeeze the hose together; as there is nothing passing through so no pressure.