Originally Posted by mikemass1221

If I blast air into the small hole (red arrow on my drawing), coolant splashes out all over the place from the large hole (green arrow).

If I place the air blaster in the main opening with a rag over it to seal it in and then let go after a few seconds, then the coolant just rushes back out. Expansion tank too low to get a good sense of what's going on in there.

I really only think we are dealing with a coolant breach, not combustion gas.

Originally Posted by funola

Have you listened at the valve cover oil fill hole while blasting compressed air into the 1/2" hole? Do this with the coolant expansion cap on.