p38 overheating

hi there everyone just wondered if any one can shed light on my problem changed the rad water pump and thermostat on my 4.0 p38 runs fine until i put my heater on high then starts to creep up also when i look into the coolant bottle i see bubbles appear i rev the car and the water level goes down then when i release the revs the water rises to normal

Seem to recall you've had this for a while, water pump now changed but its the same? Are you sure it's not down to an air lock? Maybe time to be looking for symptoms of head gasket failure.