habaneropep2019
Registered User
Dug deeper into my troubled engine (low compression on #4 and #6, 100-150 psi lower than other cylinders). Pulled the valve cover off and was greeted with this lovely sludge mess.
Did a leakage test and determined it is primarily leaking past the intake valves, though there is some small leakage past the exhaust on one cylinder. No pressure in cooling system at TDC on either suspect cylinder.
Then I dropped cylinders to BDC and loosened the rockers so valves would stay shut. Applied shop air, and lo and behold cylinder number #4 pressurized the cooling system.
While I know the valves leaking is definitely the cause of low compression, I’m worried that the cooling system pressurizing on the bottom of the stroke is indicating cavitation on that cylinder. If it was a blown head gasket I would expect it to pressurize at TDC as well, and that did not seem to be the case. The engine was low on coolant when I got it with no external leaks that I could find when warmed up, so I suspect coolant has gone somewhere internally.
Thoughts?
Did a leakage test and determined it is primarily leaking past the intake valves, though there is some small leakage past the exhaust on one cylinder. No pressure in cooling system at TDC on either suspect cylinder.
Then I dropped cylinders to BDC and loosened the rockers so valves would stay shut. Applied shop air, and lo and behold cylinder number #4 pressurized the cooling system.
While I know the valves leaking is definitely the cause of low compression, I’m worried that the cooling system pressurizing on the bottom of the stroke is indicating cavitation on that cylinder. If it was a blown head gasket I would expect it to pressurize at TDC as well, and that did not seem to be the case. The engine was low on coolant when I got it with no external leaks that I could find when warmed up, so I suspect coolant has gone somewhere internally.
Thoughts?
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