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1998 Jeep Cherokee Question: low compression in one cylinder

 

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Soc, 4.0L 6 Cylinder, Coatesville, PA, December 22, 2009, 12:28
 Rookie

i recently had a compression test peformed and piston 1 was 60psi while the other 5 were 95psi, engine is original with 184k. What could be the problem and roughly how much could it cost.

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  • Answer #1

    December 22, 2009, 14:14
     Technician

    When you find low compression in a cylinder, the next step would be to perform a leak-down test. This test is where they apply compressed air to the effected cylinder and see where the air leaks out. It will either leak from the crankcase (worn piston rings), the exhaust system (leaking exhaust valve) or the intake system (leaking intake valve). Spraying oil into the cylinder will also help to identify poorly dealing piston rings.

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    Soc, December 22, 2009, 15:06
     Rookie

    Thanks for the response, is this type of repair expensive? the Jeep has other costly "issues" that need to be addressed and this was unexpected.

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    TurboSDCharger, December 22, 2009, 15:15
     Technician

    Getting it tested isn't expensive, but worn rings means an engine overhaul or replacement, and the valves leaking is a valve job. Both these repairs will be expensive, $1000 - $3,500 is my guess. Get it checked and then get some quotes for the repair they recommend.
    Why did you have the compression checked in the first place? Is it running rough?

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    Soc, December 22, 2009, 15:30
     Rookie

    yes, i thought it was the o2 senser but when they hooked the computer up there was a list of errors and decided to do the compression test.

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