25th Nov 2012, 07:54

Had the same problem; radiator and radiator hoses staying cold no matter how many miles were done. The temperature gauge never went above half way, and didn't think it was over-heating until I was driving around the hilly lanes of Cornwall, obviously getting the engine quite hot. The piston rings started pinking, engine was bubbling and the engine management system cut the engine out (with no loss of coolant) and wouldn't start, until the engine had cooled down a bit, yet the radiator remained cold and the temperature sensor never read above half way.

I realised the thermostat was not opening, so I removed it and tested it to find it was jammed closed (faulty), so I put a new one in and everything is OK now! Water is circulating, and the radiator and hoses are getting warm. The reason the gauge only reading to half way is because the temperature sensor is on the radiator side of the thermostat, and is picking up warmth from the engine by conduction without any coolant flowing.

Mike.