Is my WJ doomed? No compression in Cylinder #1 - JeepForum.com
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post #1 of 21 Old 02-21-2020, 06:49 PM Thread Starter
v1rok
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Is my WJ doomed? No compression in Cylinder #1

Hi,

I previously reported about misfiring in #1 cylinder. (With P0301 error code.) I checked/swapped plugs, checked/swapped coils, checked wiring. Still misfiring

Today I did compression test. Did it on first five cylinders and then stopped when the patterns was clear:

#1: 0
#2: 160
#3: 155
#4: 160
#5: 160

So the issue was no compression in Cylinder 1

Am I doomed? Is it the dreaded dropped valve seat issue?


(The truck is 2003 Overland v8 4.7L HO with 137K on the clock)


2003 v8 Overland; 2013 v6 Trailhawk
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post #2 of 21 Old 02-21-2020, 07:46 PM
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Is my WJ doomed? No compression in Cylinder #1

Well, thatís not good. Pull the valve cover and see if the rocker fell off and the valve is jammed lower from a lost seat. Couldnít ask for an easier cylinder to investigate!
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post #3 of 21 Old 02-21-2020, 08:38 PM Thread Starter
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Thanks for the suggestion!

How easy is it to pull the cover? Is it like 2 hr job or 2 day job or 2 week job? (For a DIY garage mechanic)

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post #4 of 21 Old 02-21-2020, 11:14 PM
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2 hrs should get it off, and back on after a look. Like was mentioned above, thats the easy side.

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post #5 of 21 Old 02-21-2020, 11:36 PM
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Yeah.

No compression at all is likely valves or a hole in your piston. A bad head gasket wouldnít come back at zero.
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post #6 of 21 Old 02-22-2020, 12:03 AM
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Quote:
Originally Posted by sdg3205 View Post
Yeah.

No compression at all is likely valves or a hole in your piston. A bad head gasket wouldn’t come back at zero.
One more thing to check before valve cover removal, squirt a tablespoon of clean motor oil into the suspect cylinder, conduct compression test again. If there’s still no compression, it’s indeed the valves; if there’s compression, it’s the rings.
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post #7 of 21 Old 02-22-2020, 12:11 AM
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I’ve rebuilt the 4.7’s once fully, and once partially. First full rebuild was due to a fallen #8 valve ring seal. The second partial rebuild was due to a failed secondary cam chain tensioner. Luckily it somehow locked the engine, preventing valve crush. I’m nearly done with the reassembly now, just the air intake assembly and oil pan. Yep, cam chain pieces fell into the sump. The lockup was so abrupt, the crank sprocket sheared the woodruff pin.

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post #8 of 21 Old 02-22-2020, 01:39 PM Thread Starter
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Thanks, Oregon! I did the test you suggested. Squirted some oil in cylinder #1 and did the compression test again.

The results:
1st time: 165
2nd time: 90
3rd time: 15
4th time: 0

In other cylinders the compression held steady at around 160 no matter how many times I did the test.

So, what does it mean? The rings are toast?

In terms severity and cost of repairs (say, on the scale from 1 to 10), how bad is it? How much would a mechanic/garage charge for this type of work?

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post #9 of 21 Old 02-22-2020, 02:09 PM
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Even if the rings were toast, they'd have to be REALLY bad to return 0 psi. Do you have a borescope?
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post #10 of 21 Old 02-22-2020, 02:40 PM
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Good call Oregon, the oil trick helps narrow things down. I agree with sdg3205 as well though. To have a big enough hole to lose ALL compression down to zero would have to be pretty significant. Maybe a broken ring? But seems like it would take more than just worn rings to do that. And all the other cylinders seem really good. That doesn't really say the motor is just wore out. Definately need to see whats going on inside there. The borescope would be nice, but Ive got a feeling that head is gonna have to come up either way. And maybe the piston as well. Not good news for sure. Sorry v1rok!

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post #11 of 21 Old 02-22-2020, 03:01 PM Thread Starter
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No, don't have borescope at the moment. By the way, I did pull the valve cover and I saw that all rocket arms were in place. So, this eliminates that, too.

Something must be bad inside that #1 cylinder.

I got this truck ~4 years ago for just under $4k. Between my daughter and I we put about 20k miles, mostly worry-free miles. Only did the regular maintenance: oil, brakes, rotor. Plus the rear windshield wiper motor. It was mostly a weekend driver in the mountains.

So, at this point I will have a tough decision t o make.

Do I spend money (how much?) to rebuild the motor? Or do I let it go? How much can it be worth in this condition (with dead cylinder)?

2003 v8 Overland; 2013 v6 Trailhawk
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post #12 of 21 Old 02-22-2020, 03:25 PM
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Quote:
Originally Posted by v1rok View Post
No, don't have borescope at the moment. By the way, I did pull the valve cover and I saw that all rocket arms were in place. So, this eliminates that, too.

Something must be bad inside that #1 cylinder.

I got this truck ~4 years ago for just under $4k. Between my daughter and I we put about 20k miles, mostly worry-free miles. Only did the regular maintenance: oil, brakes, rotor. Plus the rear windshield wiper motor. It was mostly a weekend driver in the mountains.

So, at this point I will have a tough decision t o make.

Do I spend money (how much?) to rebuild the motor? Or do I let it go? How much can it be worth in this condition (with dead cylinder)?
Well you can always run a leak down test to confirm, but it does sound like an issue with the piston. I vote inspect, then decide. If the piston is toast but the cylinder cross hatching is still good, just replace the piston and rings. New head gasket and done. You can always have more things done, but that's certainly the cheapest option.
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post #13 of 21 Old 02-22-2020, 03:53 PM
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Or just swap out the complete engine assembly. More than likely the old one has to come out either way. Some of the more reputable wrecking yards offer a six month warranty.



More than likely, you wont get much money out of it without a good running engine, they go for just a couple hundred bucks around here with engine/trans problems. Thats kinda how i got mine, PO thought it had PCM problems, but it didn't. I picked it up for 500 bucks.

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post #14 of 21 Old 02-22-2020, 05:18 PM Thread Starter
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Originally Posted by sdg3205 View Post
Well you can always run a leak down test to confirm, but it does sound like an issue with the piston. I vote inspect, then decide. If the piston is toast but the cylinder cross hatching is still good, just replace the piston and rings. New head gasket and done. You can always have more things done, but that's certainly the cheapest option.
Sdg, can you describe how to do leak down test?

I read somewhere here that even to replace head gasket would cost more than $2K (at a shop). I donít think I will have time to do it myself. (Maybe if I were retired, I would consider such project. But not anytime soon.)

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post #15 of 21 Old 02-22-2020, 11:25 PM
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Going in that deep is never cheap unless you do it yourself. 2000 to do both heads and all the misc pieces and parts along the way is not unreasonable. If you swap the entire engine, it may save some labor time, but the price of the engine included might not save you alot. Either way, this one is gonna hurt. If the rest of the Jeep is in good shape, and you think you can get a couple more years out of it at least, then it may be worth the repair. If the Jeep is barely hanging on in other ways along with this issue, it may be time to sell for parts.

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,3"BBfront,2"BBrear,JK'sW/32's
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