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Next step on loss of compression

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Old Aug 6, 2010 | 08:31 PM
  #1  
always89's Avatar
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Model: Cherokee
Default Next step on loss of compression

Ok, No 1 cylinder is at 30 PSI. Did a wet test. No change, Leakdown drains FAST. So, I pulled the head. No signs of a gasket break, and it looks like the valves are seating. (I did a light test. Dark room, put a flashlight on and around the valves and looked into the chamber. no light getting through)

So, I start looking at the cylinders. I can actuallymove #1 side to side about a 16th of an inch. But, I can see the ring is intact (at least the top one)

Any suggestions as to what I can do to further trouble shoot this thing?
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Old Aug 7, 2010 | 06:32 AM
  #2  
Pa XJ's Avatar
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From: Barnesville, PA
Year: 90
Model: Cherokee
Engine: 4.0
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on the leak down test, if it drained fast your should have been able to hear where the air was going to, either out intake exhaust or crankcase, if u did not and already took it apart well thats a problem as now you have no clue
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Old Aug 7, 2010 | 07:56 AM
  #3  
CAEMI's Avatar
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From: Detroit, MI
Year: 1994
Model: Cherokee
Engine: 4.0
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Pa XJ is right. The point of the leakdown is to pinpoint the leak. Too late for that.

You could pull the oil pan and remove the con rod big end cap and pull that #1 piston out. Probably has a broken compression ring and it's an easy fix. Hone the cylinder and refresh the rings on that cylinder. You'll have one lung slightly stronger than they others...which can cause problems MAYBE but is unlikely. Button it up and drive. Be careful to gap the rings correctly...it is easy to do with feeler guages. Just take a minute to learn what the feeler guages "feels" like in a known gap (like a dial caliper).

TTFN
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Old Aug 7, 2010 | 09:21 AM
  #4  
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From: Keesler AFB, MS
Year: 1998 XJ
Model: Cherokee
Engine: 4.0L
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Get the head magnafluxed and pressure tested. I had lox compression in my number one and it turned out i had a crack in number one and in number two. after he said that i told him to stop looking bc i needed a new head anyways. the bad crack was in between the two valve seats in the number one cylinder. Couldn't see the crack in cylinder 2 with the naked eye

And X2 on the leak down test
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