Monkeynuts321

Hello I have an old mk2 p38 2.5 dse diesel its doing my head in it overheats I have put a new head gasket and head on and expansion tank and radiator waterpump thermostat and clutch on the main fan it starts and ticks over great but when I drive it it stays normal the temp gauge but as soon as I stop it overheats I'm baffled can anyone give me advice please