Right , I've got a RR workshop manual for b series engines and it says that overheating could be caused by:-
loss of coolant
faulty thermosatat
faulty coolant pump
weak mixture
faulty lubrication
faulty ignition timing
incorrect tappet clearances
fouled coolant system.
Today I had the b80 idling for around 5 minutes or so after topping up the coolant levels. The pipe to the top of the rad became very hot quite quickly, too hot to rest your hand on for very long so I recon the thermosat and water pump must be working reasonably effectively. The pipe returning from the bottom of the rad became warm so the rad must be cooling the water and again water pump must be circulating water. Are these fair assumptions? Seems to be ticking off numbers 1, 2, 3 and 8 in the list.
I tried to get the thermostat out but couldn't get the housing apart, didn't want to damage it by prying it too hard.
How do you tell if there is a weak mixture? The altitude control is in the correct position.
Thanks for any ideas
Paul