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Jeep Liberty KJ and KK (2002 - 2012) Technical forum for all Jeep Liberty (also known as Cherokee in non-US markets) vehicles.

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  #16  
Old May 6th, 2017, 10:33
cushdaddy cushdaddy is offline
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Re: KJ question sorry.

Well, I figured it out. The key on the crank that drives the timing gear failed. There was about 10 degrees of rotation on the gear. That key design is stupid. There is just one little tab that engages the gear and it broke. It looks like the key is hardened. Case hardened possibly. I'm going to check it at work Monday. Nobody local has the key so the dealership won't have them till Tuesday. This makes more sense to me than 4 bad sensors. I'll update this when I get it back together. Only question is should I replace the gear?
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  #17  
Old May 7th, 2017, 08:16
trippled trippled is offline
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Re: KJ question sorry.

If the gear shows any damage or is questionable in any way then yes.
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  #18  
Old June 6th, 2017, 10:00
burntkat burntkat is online now
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Re: KJ question sorry.

Quote:
Originally Posted by cushdaddy View Post
Well, I figured it out. The key on the crank that drives the timing gear failed. There was about 10 degrees of rotation on the gear. That key design is stupid. There is just one little tab that engages the gear and it broke. It looks like the key is hardened. Case hardened possibly. I'm going to check it at work Monday. Nobody local has the key so the dealership won't have them till Tuesday. This makes more sense to me than 4 bad sensors. I'll update this when I get it back together. Only question is should I replace the gear?
I have no experience with that engine-0 but it sounds like a woodruff key. This has been used to hold crank pulleys on engines with no problems for years such as the SBC crank pulley. Works just fine.
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  #19  
Old November 17th, 2017, 11:18
WB9YZU WB9YZU is offline
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Re: KJ question sorry.

Old thread, but, I think he meant Timing Gear.

The most common time you see this failure is a failure of the cam bearings.
With the advent of using aluminum heads and cams running in the head, oil starvation can cause the aluminum in the head to seize to the cam; which breaks the key.

The Damper is also held by a key, and a huge bolt. I've not worked on an engine that wasn't this way.
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  #20  
Old January 13th, 2018, 13:42
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Ecomike Ecomike is offline
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Re: KJ question sorry.

Seems to be a few liberty folks who might be able to reply to this:

Any one know anything about the 2010 Jeep Liberty V-6 engines?

Trying to figure what the rest of the story is. What started out as a head gasket job (coolant leak), a week after it was done by an engine shop, ended up with 2 bent valves and wiped lobes on the Cam shaft with no other possible cause or casualty than the timing chain adjusters being weak (or not adjusted well enough/properly, when the head was pulled?) and later replaced with the 2 new valves and a used good Cam shaft.

<100,000 miles on the rig. They claim there was no piston damage.

Still has a random misfire, but no CEL light now, and a miss at idle once it warmed up (Runs fine on a cold start) and misses at 4000 rpm.

None of this makes any sense at all!!!! Pretty I am not getting the truth, or the whole story.
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  #21  
Old January 13th, 2018, 13:58
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Green Mesa XJ Green Mesa XJ is online now
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KJ question sorry.

Something is off. Those 3.7 are do not like getting too hot so head gaskets can be common (like every aluminum head engine). Iíve heard about those engines dropping a valves but Iím not sure how common or what the cause is. I think it was more common 2002-2004 but donít know for sure.

My guess is the head the put back on was not from that under 100k motor, they probably either farmed the job out locally for a rebuild and that local machine swapped it for one already the shelf or got a national rebuild companyís garbage head off a very abused motor. Other than that the damage to that head makes no sense unless the rebuild was out of spec and the damages followed.

Injectors can cause misses with no CEL, upto a outright fail the computer ignores it if itís more mechanical and the injector is electronically responding correctly. Coil packs can cause issues I believe that design is three coil packs with a spark plug wire going to the other sides cylinder. Anything but mopar coil packs are prone to early failure.

Iíd pull compression on that motor just to see what the hells going on. BTW that motor likes to be high compression.


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  #22  
Old January 13th, 2018, 14:19
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Ecomike Ecomike is offline
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Re: KJ question sorry.

All the work was done by a very old established motor rebuilder (with a not so good reputation in the old days). They replaced the Cam with a used one. They did NOT swap heads, they just cleaned/serviced the valves only on the heads (My guess is that means they cleaned it and replaced the valve stem seals). They said nothing about resurfacing the heads or block, but in answer to my questions he said the heads themselves were fine, no cracks. My son had the jeep all over the country last year, 10 months many miles with only one part replaced, the oil pressure sender went bad, and one coil pack replaced to solve a specific cyl miss fire code, that was done about 2-3 months before the head gasket failed. It was leaking/loosing coolant very slowly about 8 weeks before the head gasket job. Lost maybe 2 gallons of 50/50 blend in weeks, about 2000 miles. He also replaced 5 spark plugs when he replaced the coil pack. Could not access the 6th spark plug.

The motor shop guy told me all 6 cylinders have 155 psig compression.

I did not realize the Liberty engine was over head Cam. Until last night when I went to the shop with my son to pick up, I had been told they were replacing the crank shaft, LOLOL. So at least I now have that part of the story straight from the horses mouth LOL.

But now I am wondering how you bend a steel valve stem, in an aluminum head, with out damaging the head???? And the piston???



Quote:
Originally Posted by Green Mesa XJ View Post
Something is off. Those 3.7 are do not like getting too hot so head gaskets can be common (like every aluminum head engine). Iíve heard about those engines dropping a valves but Iím not sure how common or what the cause is. I think it was more common 2002-2004 but donít know for sure.

My guess is the head they put back on was not from that under 100k motor, they probably either farmed the job out locally for a rebuild and that local machine swapped it for one already the shelf or got a national rebuild companyís garbage head off a very abused motor. Other than that the damage to that head makes no sense unless the rebuild was out of spec and the damages followed.

Injectors can cause misses with no CEL, upto a outright fail the computer ignores it if itís more mechanical and the injector is electronically responding correctly. Coil packs can cause issues I believe that design is three coil packs with a spark plug wire going to the other sides cylinder. Anything but mopar coil packs are prone to early failure.

Iíd pull compression on that motor just to see what the hells going on. BTW that motor likes to be high compression.


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  #23  
Old January 13th, 2018, 14:59
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KJ question sorry.

Thatís fairly low compression, for a 3.7 Spec is 170-225. my 2006 3.7 gunked to death by the previous owner had cold compression of 165-175 with like 150k miles on it. Actually that engine was ok except for the gunk, it got to the pan and pickup tube. Swaped it out anyway with a low milage 2012, to get the pan off in the vehicle was half the job of removing it, figured we were better off grabbing a low milage JY engine.

3.7 is not a bad motor over all, but because it has aluminum heads itís prone to failures the 4.0 never had.

How did the headgasket fail and not warp the aluminum? Iíve done jobs on cars where I know they never reached operating temperature let alone overheating and the head was not warped, that was because the material Toyota use for headgasket was the weak link, as I recall the 3.7 is a metal gasket. Iím curious how the gasket went bad if it didnít overheat. If it did overheat Iíd think there should be warping.
The timing chain shouldnít have much stretching at that milage and tensioner shouldnít have failed either.
Dunno something seems off about the repairs being done.

The miss could be whatever brand coil pack was used, the cheap Chinese packs tend to fail. Or spark plugs/ old spark plug, itís another jeep that doesnít like anything but oem plugs. I think they are 35-45k replacement schedule. Getting to the spark plugs on the Commander isnít tough, but we have 6 coils, maybe they had more room to get the coil pack out.


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  #24  
Old January 14th, 2018, 21:18
WB9YZU WB9YZU is offline
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Re: KJ question sorry.

I've had head gaskets fail and not cause issues with the head/block.
The issue was over pressuring of the cooling system, quite common on early 70's Renaults due to a sticking release valve.

In the locally remaned head dept, I've had valve jobs done by supposedly experienced machinists that came back with the valve stems looking like crooked teeth with their acceptable tolerance being +/- 1/8" at the stem.
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