overheating

my 4.0 p38 keeps overheating i have had a new water pump which was leaking and thermastat fitted which has not solved the problem. i have had a head test done which was ok has anyone got any ideas.
thanks

A few questions. Have you had the car long or just bought it? How well kept is the service book? What colour is the oil - black, grey or golden brown? The 4.0 is often notorious for the engine bore internal liners giving up the ghost. They can become porous or drop which consumes copious amounts of water. This wont show up on a compression test. Sometimes it sounds like a knocking camshaft. Could be a warped cylinder head too. In any event its not a cheap fix if its either of these probs.