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Old 12-07-2006, 09:45 PM   #1
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Default Compression test results

Hello,

This is my first time posting, I've searched for and read many posts about compression checks on this board, but none of those people'* results seemed as varied as mine.

My engine recently stopped running and now won't start, when I pulled the plugs, #1,3,5 were extremely wet, it looked like antifreeze, leading me to think I am another victim of a bad UIM. I changed the #1,3,5 head gasket a few months ago and I noticed the area on the UIM around the stove pipe was all ashy, but I put it back together anyway.

I am trying to figure out if my short block is trashed, or if a wet test doesn't change these readings that I may get away with just changing the UIM and the heads, or what would happen if all I change is the UIM? My cylinder readings vary by almost 64% from 3&4 to #5, what are the chances #5 has broken rings, or could it be ruined valves? Will the wet test rule out broken rings? I would be fine with replacing the heads, but I would love to not to have to touch the short block.

I ran out of daylight to do a wet test, but here are my dry test results.

#1 - 120
#2 - 140
#3 - 170
#4 - 170
#5 - 110
#6 - 130

Thanks for any advice.
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Old 12-08-2006, 12:11 AM   #2
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You really shouldn't have much more than about 10% variation between the readings. Let us know what the wet readings are when you get them.
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Old 12-08-2006, 07:22 AM   #3
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Soon as I saw you name I hardly needed to read further.

http://www.bonnevilleclub.com/forum/...e=article&k=38

Rings are less common in the 3800 than head gaskets. And head gaskets are extremely UNcommon.

My thoughts are you still have some water in cylinders etc that are causing your variation.
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Old 12-08-2006, 11:10 AM   #4
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Compression numbers are likely not reliable under the conditions you used to obtain them. Fix the UIM/LIM as advised in linked article above first.
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Old 12-08-2006, 04:30 PM   #5
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Okay, here are my wet and dry readings

Dry results
#1 - 120
#2 - 140
#3 - 170
#4 - 170
#5 - 110
#6 - 130

Wet results
#1 - 150
#2 - 120
#3 - 190
#4 - 160
#5 - 125
#6 - 170

My battery was going dead on #2 & #4, which I think is why the numbers went down. I pulled off the UIM, and there was a large hole in the wall the stove pipe passes through, probably almost 1/4 inch in diameter, and the lower intake looked like a lake of antifreeze. Luckily I had already changed the lower gaskets when I did my head gasket change a few months ago, I just wish I would have known about the UIM problem last time I had it apart, this is my first 3800.
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Old 12-08-2006, 05:52 PM   #6
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Based upon your symptoms and descriptions.. I feel the advice given is extremely sound.

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Originally Posted by bill buttermore
Compression numbers are likely not reliable under the conditions you used to obtain them. Fix the UIM/LIM as advised in linked article above first.
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