tried a new bleeding this afternoon .
bottle level expanses until overflow (it takes approx 15 miles drive)
but what surprises me is that when cold , the level doesnt decrease .
Does it mean that air is not allowed to enter trhrough the bottle cap when temperature (and so pressure) decrease ?
If the level in the expansion tank rises but doesn't get drawn back into the system as the engine cools then air is getting in from elsewhere. A full cooling system pressure test is needed to find it.