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Old 08-18-2016, 01:35 PM   #1
City: Caribbean
Country: St. Thomas
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Having issues with Lehman SP 135

Good afternoon all, My 1990 Lehman SP135 engine has developed a noise while running that sounds like an exhaust leak coming back through my air intake manifold. I noticed this once recently right after start up a month or so ago but it went away within a few minutes and didn't occur again until we were following the Anguilla Championship sailing boats Sunday afternoon while coming back. This time the noise was accompanied by what sounded like tappet noise as well.

My first thought was that I had a valve sticking, or not closing properly, so I followed forklift's valve adjustment guide to a tee actually going through the process twice just to make sure I got everything correct but unfortunately, After valve adjustment, the tappet noise went away, but I still have the issue of what sounds like exhaust noise (popping noise)coming out of the air intake manifold. Does anyone have an idea of what is causing this?

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Old 08-18-2016, 03:15 PM   #2
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Burnt valve? A leak down test where you pressurize with compressed air each cylinder through the injection hole can identify it.


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Old 08-18-2016, 05:04 PM   #3
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I agree
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Old 08-18-2016, 06:20 PM   #4
City: Caribbean
Country: St. Thomas
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Good advice, and I won't have to pull off anything. I Googled "diesel engine popping through the exhaust" and read that the cause is the exhaust valve not opening properly and the compressed gasses are exiting the intake valve when it opens, so I turned the engine over with the stop valve closed and saw that the rockers were all going up and down normally which I believe would take a bent push rod or faulty lifter out of the equation and also noticed that the popping comes when valve #3 opens which I believe is the #2 cylinder intake valve. Now I'm really stuck trying to figure this out and your advice seems like a good next step. Thanks.
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engine issues, engine problems, ford lehman, lehman 135

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