I have a 1998 Renault Megane 1.4 with an unusual overheating problem. It boiled over ecently during 1st and 2nd gear work on the Hardknott Pass in
the Lake District. It's just been to the garage as the electric fan wasn't kicking in, and had a new radiator thermocouple switch, thermostat and refilled with antifreeze and the system bled.
The problem now is that from cold or when the engine has been allowed to cool down for 40 minutes or more on running it the temperature goes well into the danger zone and coolant boils over from the expansion tank. Immedately that happens the temp drops to usual running temp and runs as
normal with no overheating, but if I let the engine cool down and top up again the problem occurs again. The elctric fan is working and keeps cutting
in to allow it to run at normal temperature. Sometimes just before it boils over threough the expansion tank I hear a whining type noise. It's not the fan operating but could it be the water pump?
Initially I thought the head gasket might be blown but the car runs as normal (not misfiring) and there is no water in the oil. Like I say, the problem seems to be from a cold engine and once it's boiled over the
temperature stabilises and the heater is normally warm although I wouldn't say it's hot.
It's been back to the garage a couple of times and they are unable to determine what's happening.
Any suggestions please?