Land Rover Repair: 1994 Discovery 3.8L V8, USA, discovery 3, expansion tank

Question
I have an overheating problem. At idle the disco stays around normal temp, but once I get on the highway the temperature starts to creep up until it boils out of the expansion tank. What do you suggest I do?

Answer
90% it will be cylinder head broken, or gasket burnt problem. So, try to go for a few minutes from till when the engine is preheated to normal, and then stop the engine and check the water tube at the top of the cooler. If that is very hard than you should remove cylinder heads.