Another nice day today so made the most of it. First I took her outside and ran the engine up to temperature to check if there were any coolant leaks under pressure. Initially it looked OK, but then I saw a very small drip. Confusingly it was nowhere near any of the cooling pipes, and a quick taste test showed it was petrol. It turned out to be a leak where the fuel line goes into the pressure regulator.
Amazingly the jubilee clip was actually loose and took about 6 turns to
tighten up. I have absolutely no idea how long that leak has been
there, but it could have been months as I very rarely run the engine
with the bonnet off.
So a very useful exercise. and when I checked
later when the engine had cooled down the coolant was at the same level
in the expansion tank. Good news. I will still need to do some
more runs to confirm it, before I go on the 100 mile+ Stilton Cheese run
in April, but there is plenty of time.