Hi. Hoping for a heads up on a prob with 200tdi (disco engine), now in my Rangey. Coolant is pressurising on start up, no heating, runs fine, bit lumpy to begin with but settles and revs freely with no mis-fire. Oil clear of any milky signs, both at cap and on dip stick. Immediate thoughts were head gasket, but clear oil and no mis-fire?? If run with cap off expansion tank there is a fountain of water pushed out, immediately on start up. Temp gauge showing norm now, but when this all kicked off coming back from Wales did get proper hot. After stopping , cooling and refilling, the pressure was there, although managed to nurse it home with no further overheating on gauge, no heating though. Got me by the short and curlies this one!!!! Any help much appreciated. Ta, Peter

Air lock or more likely head gasket has gone right next to a waterway and is pressurising the coolant.

Forget emulsion in oil or oil in water. that will only happen if it blows near an oilway.

got to say it dose sound very much like head gasket

i second that mine did that a few months ago was gone between piston no2 and the waterway and was forcing the air into the water

could it be the water pump?