Hi

Thanks for the replies...A bit of history
1) All 3 sensors on the engine are new.
2) Thermostat, expansion tank and pressure cap are new
3) Tested everything for the fan circuit - relay, resistor, fuse

I read on the archives that if you have residual pressure in the coolant, it may mean that compression is somehow leaking into the cooling system. I'm thinking that it only happens at extended idle conditions so it may be in the high speed fan circuit. Will try another fan switch to see what happens.

Anymore comments? Anyone?

Thanks

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1992 124 E200 (Euro)