Tim - I am starting to think this is it!! Just been out and had the car up to temp, reved it etc and coolant stayed where it was suppose to - watched the catch tank - lots of venting (is that normal?) with a little condensation. No leaks, coolant did not reach the cap, rad hot on one side and warm on the other, coolant flowing to the bleed t What pressure should the cap be? the new one says 16psi - no idea on the original. Temp got to mid 80s on tick over then up to 88ish, with a bit of revs came back to mid 80s and the fan came on at 81 as normal and stayed on. So got 5ltr of coolant coming and will take this with me to the fish and chip run, take it easy and top up as I go