a friend of mine has bought a 96 range rover 2.5td that keeps over heating. After about 50 miles the temp gauge shoots up as far as it will go. Although there are no signs of boiling when it has coolede down most of the water has gone. He has replaced the thermostat, heater matrix, radiator and water pump but has not cured it. Otherwise it drives fine so he is reluctant to go down the road of head trouble s there is no missing and plenty of power. Any got any ideas? Any advice or tips would be well apreciated.