Just been for a spin in the car, got 5 mins from the house and the temp was up at 100 degrees. I pulled over to the side of the road as this sort of temp usually takes around 15 mins minimum on a warm day - today is about 12 degrees in London. The water level is fine, and the header tank is cold. The heads and inlet manifold are really hot and the belt on the waterpump/alternator looks fine. Anyway I let it cool off and went straight home. I'm pretty sure its not an airlock as I have a rear bleed off the inlet manifold back to the header tank. I checked the belt was turning the pump pulley - it is. The water level in the header was still fine when I got back and the heads are still really hot. The coolant pipes to the rad are hot in the engine bay but cold at the front of the car and the heater isn't getting warm. It seems like the impellor has come loose inside the pump housing - anybody seen this before or have any advice ???