I did about 6-8 revolutions per cylinder. The car has about 150,000 on it which isn't a lot and I have changed the oil regularly since I took ownership. I am really not sure about the HF gauge but I suspect it could only open at a higher psi. It sounds like either way I am looking at removIng the head. The coolant sounds like it would make sense as there was a noticeable difference in the appearance of the injectors on the cylinders with no cOmpression.