Overheating The red flashing coolant light suddenly began to flash and we found a very low coolant level. We filled to coolant resevoir and drove 20 mins. The coolant was boiling and the car overheating. The mechanic has checked the head gaskets whicha are OK. He replaced the sensors and the thermostat, but it continues to overheat. He checked the fans, all OK. No leakage indicating the water pump is gone. Help!!!

Hi,
If the car is overheating it could be due to a thermostat which is stuck in the closed position, a failed water pump or just a slack belt driving it. I think there will be a "little" tube carrying coolant from the engine to the coolant expansion tank, and if you run the engine with the filler cap removed you should see water coming through that pipe IF the rump is running. A failed water pump will not necessarily leak, it just won't pump the water round the engine.

Always take care when dealing with a pressurised cooling system on an overheating engine - the water may well be above boiling point.

If you run the engine without coolant the cylinder head may well warp and repair bill will be huge.

Hope this helps you a bit. D