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I recently performed a cylinder leakdown test searching for a cause for oil loss. On 5/6 cylinders, I pumped it up to 90 psi on the left gauge and the right gauge was between 75-80. Only 1/6 wouldn't go past 65. I put my hand on the intake for that cylinder on the plenum and didn't notice and leaks, then put my hand on the exhaust pipe and there was maybe a very low flow. The air may have been going past the cylinder rings and into the crankcase but I'm not sure how to check that.

How bad is a 30% leak, especially if it's on the exhaust side ?

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    You check airflow into the crankcase by pulling the oil filler cap.
    – Ben
    Commented May 7, 2016 at 17:07
  • and you're sure the exhaust valves were closed?
    – Ben
    Commented May 7, 2016 at 17:15
  • If they weren't closed, I'd be getting 0. I did the test on that one multiple times
    – amphibient
    Commented May 7, 2016 at 17:21
  • 30% indicates a problem. how is compression and engine vacuum?
    – Ben
    Commented May 7, 2016 at 17:25
  • @Moab Put your comment as the answer.
    – DucatiKiller
    Commented May 7, 2016 at 22:34

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"put my hand on the exhaust pipe and there was maybe a very low flow."

You have found your problem, there should be 0 flow.

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  • Additionally this sounds like a possible bent, or burn valve or valve seat. Recommend taking a look inside of the cylinder with a borescope if possible. I'd hazard that there's carbon build up on the valve preventing effective sealing. Anything short of taking the head off would be guessing.
    – Jeep Cherokee Rescue Society
    Commented May 8, 2016 at 10:36

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