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Unread 08-07-2010, 12:53 AM   #1
97DCZJ
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Bad piston rings?

99 WJ 4.7L, 149xxx miles.

I burned almost about 5 quarts in 3,000 miles, obviously keeping it up to level throughout time, just all added up to that. I don't overheat, and I just changed the oil and it wasn't milky, and replaced the radiator and coolant seemed pretty good so that throws bad head gasket out of the question. It puffs blueish smoke sometimes at start, but puffs from stopsigns/stop lights almost everytime. Just replaced the PCV valve, and old one seemed to be fine anyway.
I almost have this down to almost bad rings or valve guides. How much of a PITA would it be to pull the motor and fix these?

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Unread 08-07-2010, 12:59 AM   #2
ratmonkey
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A big pita actually.
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Unread 08-07-2010, 08:49 AM   #3
comptiger5000
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Do a compression test, see what it comes back as. Then, add about a teaspoon of oil to each cylinder and retest. If the compression goes up, it's bad rings. If it doesn't, it's valve guides. If that test shows it's rings, they may just be stuck, not bad.

To try to free up stuck rings, buy a quart of Marvel Mystery Oil (MMO). It's about $5. Pour an ounce or 2 into each cylinder through the spark plug hole (leave the plugs out). Let it sit overnight. In the morning, place some rags in front of the spark plug holes, and crank it for a few seconds to push any remaining oil (that didn't seep down past the rings) out. Use the rest of the quart as your top-off oil until you finish the quart. Run the oil/MMO mix for about 1000 miles, then change the oil and filter. If the rings were gummed up and sticking, this should clean them up a good bit and reduce your oil consumption.
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Unread 08-07-2010, 09:03 AM   #4
Howiedooit
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on a daily driver stuck rings are unlikely, worn rings are also unlikely with only 147k, if the problem began out of the blue then I'd lean more towards a cracked ring. If you do have a cracked ring then fixing it becomes a little more complicated depending on weather it dislodged from it's groove and had a fight with your cylinder wall on it's way out. X2 on the comp test tho
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Unread 08-11-2010, 04:09 PM   #5
99_WJ_Laredo
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Quote:
Originally Posted by comptiger5000 View Post
Do a compression test, see what it comes back as. Then, add about a teaspoon of oil to each cylinder and retest. If the compression goes up, it's bad rings. If it doesn't, it's valve guides. If that test shows it's rings, they may just be stuck, not bad...
What are the compression numbers supposed to be for an engine in good condition?
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Unread 08-11-2010, 04:33 PM   #6
Bama_WJ
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Quote:
Originally Posted by 99_WJ_Laredo View Post
What are the compression numbers supposed to be for an engine in good condition?
Good info here...

compression check - Dakota Durango Message Board
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