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Old 02-04-2011, 02:59 PM
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Angry 0 compression in cylinders 5 and 6!!!!

ANY HELP OR INFO.
Compression test revealed no compression in cylinders five and six...
maybe broken gasket or something. I am not a mechanic so I dont know what would cause this... Any thoughts? cost etc.? Im always up to date with my oil changes and I have fairly new spark plugs as well.
The jeep is in the shop now. I cant wait to get my baby back.
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Old 02-04-2011, 03:04 PM
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Re: 0 compression in cylinders 5 and 6!!!!

OH and BTW, I have put 156,000 miles in this baby...
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Old 02-04-2011, 03:53 PM
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Re: 0 compression in cylinders 5 and 6!!!!

its pretty clear you need a motor.

plenty 3.7 for cheep on ebay with way less miles.
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Old 02-04-2011, 05:06 PM
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Re: 0 compression in cylinders 5 and 6!!!!

Im afraid that your right... but im trying to figure out what would be more cost efficient also... I know that is a major job... Its going to eat into my pocket book either way but do you think an engine swap will be necessary???
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Old 02-04-2011, 05:57 PM
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Re: 0 compression in cylinders 5 and 6!!!!

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Originally Posted by jeeprs86 View Post
Im afraid that your right... but im trying to figure out what would be more cost efficient also... I know that is a major job... Its going to eat into my pocket book either way but do you think an engine swap will be necessary???
if you are mechanically inclined...pull the head off to see what your pistons and the walls look like. could be valves that are bad. if it were my call, either get a rebuilt engine or engine from a junk yard. did you have a problem with the engine leading up to this?
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Old 02-04-2011, 07:28 PM
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Re: 0 compression in cylinders 5 and 6!!!!

Do the 3.7's have 2 spark plugs per cylinder? Perhaps 2 of them are loose or broken?

Is it making any ticking noises? As long as the crankshaft and connecting rods are working it may just be a gasket. I say pull the heads, i dont think it could make things any worse at this point
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Old 02-05-2011, 02:16 AM
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Re: 0 compression in cylinders 5 and 6!!!!

I know when lifters get tired on the 4.7l they drop the rockers off the lifter... dependant on what rockers dropped it could act like no compression (for example, intake valve not opening would not allow air to be drawn in which would prevent compression from building).

If a rocker is off, you need new lifters and rockers.

could also have dropped a valve seat in which case it is just dependant on the severity of the damage. Dropping valve seats is another cause for rockers falling off as the valve doesnt come all the way back up allowing the rocker to fall off (at least that is what ive seen).
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Old 02-05-2011, 03:10 AM
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Re: 0 compression in cylinders 5 and 6!!!!

Quote:
Originally Posted by ny450es View Post
if you are mechanically inclined...pull the head off to see what your pistons and the walls look like. could be valves that are bad. if it were my call, either get a rebuilt engine or engine from a junk yard. did you have a problem with the engine leading up to this?
No problems with the jeep thus far, this is a first.
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Old 02-05-2011, 03:11 AM
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Re: 0 compression in cylinders 5 and 6!!!!

...And the rocker arms checked out fine.
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Old 02-05-2011, 08:29 AM
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Re: 0 compression in cylinders 5 and 6!!!!

check if the pistons (5 and 6) are moving. use a wrench or socket on the harmonic balancer pulley nut to rotate the pistons. you can also check the oil for debris or change of color.
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Old 02-07-2011, 07:27 PM
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Re: 0 compression in cylinders 5 and 6!!!!

so... Im getting a new engine, with 29,000 miles for $4,000 installed. I had a quote from another shop for $4,650 for a 60,000 mile engine installed-But that seemed like too much for the amount of mileage. So I think Im getting the best deal with the shop where I have the jeep now. I had 156,xxx miles on the old engine and I pushed that thing to 120mph too many times to count. Im anxious to see my baby with a new engine.
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Old 02-07-2011, 07:49 PM
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Re: 0 compression in cylinders 5 and 6!!!!

Did they tell you findings? or did they just suggest a motor? compression tests, or leakdown results? did they pull the heads off (or one head for that matter)?

I fully respect just cutting your losses and throwing a motor in, sometimes you get a vehicle in such as yours with alot of miles, an owner that pushes it hard, sometimes its eaiser to say "we can spend 6 hrs pulling the heads and front cover only to find there is enough damage to warrant a motor replacement only to add on the 6hrs ontop of the engine or just assume that its had enough and just do it with no additional diagnosis costs". Maybe thats what they did but I am just curious as to no compression on the back cylinders on 2 different banks.

btw 4k is great, Last engine I did was a 4.7l, given it was a mopar reman engine with 0 miles on it, but it was 9.5k out the door
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