hgf maybe

[T-Cut]

Originally Posted by Steve42

- - - holding a lot of pressure in the coolant system.

Holding it for how long? Even when stone cold?

With air locking, the system pressure will rise faster than without and may well eject some coolant from the cap. However the pressure will drop back to 'zero' when the system cools back to ambient. If the coolant level is checked, then you establish ambient pressure in the system. After running the engine under driving conditions, the pressure will again rise, but should drop back to ambient ('zero') when it fully cools down. Any significant pressure remaining at that point is not good.

You could try the cold pressurisation test for exhaust gas by running the stone cold engine at high revs for a minute or so, then stop the engine and open the cap. No significant pressure should be released since the system hasn't warmed up.

TC