My heater exit is high on the scuttle which means that the return into the expansion tank is slightly lower than the top heater matrix pipe. Is this going to cause me a problem?

Dave B

Header tank or expansion tank? if it's the header tank ie the ONE fluid reservoir in the system with a pressure cap then as long as the level of fluid in the tank is above the pipe you'll be fine - if it's an expansion tank then it makes no difference as long as the outlet pipe from the header tank is at the bottom of the expansion tank.

Bored of explaining this but in simple terms an EXPANSION tank just is an unpressurised container that collects water that has been forced out of the cooling system past the pressure cap if it gets too hot so it can be sucked back in as the engine cools. A HEADER tank is the important one as it has the pressure cap that ensures the cooling system is pressurised so it has a higher boiling point than it otherwise would. It can be part of the radiator (if the radiator has a pressure cap on the top) or remote btw. Anyone who tells you otherwise tbh doesn't know what they are talking about or is trying to be unnessisarily confusing

Thanks for the information...
Dave B