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Unread 02-08-2011, 04:54 PM   #1
350zmarty
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When to Change out Timing Chain

Hi Folks, what is the recommended mileage to replace the timing chain and tensioner? I just bought my 96 Classic 4.0 automatic, with 153,000 miles. It runs perfect, and these engines are well known to last, but I want to keep it running great as well.

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Unread 02-08-2011, 05:03 PM   #2
Paradise XJ
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Don't know the recommendation but:

My 90 XJ just passed 230K, the chain has never been replaced. I'm replacing the failing harmonic balancer on the 88 MJ and will be assessing the look of that one at 170K. I should probably do the same to the XJ but...no symptoms...so, if it ain't broke...etc.

Just be happy it's a chain and not a belt. Just keep it well lubricated.
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Unread 02-08-2011, 05:04 PM   #3
tjwalker
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No need to replace it unless you have symptoms pointing to them.

They are VERY hardy.
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Unread 02-09-2011, 01:40 AM   #4
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I've seen them slap the block at 70k and seen them tight at 200k. Its a crap shoot, but don't rear into them unless you have another reason to be in there or your have symptoms.
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Unread 02-09-2011, 02:27 AM   #5
1990JEEPXJ
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i say that if your engine begins to feel a little under powered but runs fine then why not do it as preventative maintenance? if any of you with higher mileage engines take your oil pan off, you can check the slack in the chain and ill bet youre surprised. about 30k ago i probably had at least 1/2" of slop. i plan on changing mine at 200k just for good measure. i would rather it not break while im driving, or to have it become stretched enough to make my engine run noticeably poorer.

http://www.jeepforum.com/forum/f11/timing-chain-179k-pics-460596/
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Unread 02-09-2011, 04:50 AM   #6
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I was considering doing this, because I've replaced alot of stuff on the motor tune up wise, and the entire suspension ect.

However as a mechanic and an avid car buyer, when I see new timing chain, I normally think it must have snapped, because its not something most people do. Timing belts are common to be changed on hondas, thats about it.

IDK how I feel about this, just weird that everytime I start thinking about something to do to the jeep, a thread pops up about it within 24 hrs.
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Unread 02-09-2011, 06:46 AM   #7
ratmonkey
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Even ig the timing chain breaks you won't have catastrophic engine failure like most imports.
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Unread 02-09-2011, 06:55 AM   #8
Azzy
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Thats because of the low tolerances. if the valve clearance was like that on some of the newer 4's and 6's... bam! Toast!
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Unread 02-09-2011, 10:25 AM   #9
cbr900
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your engine will let you know, its just one of those things that will break when it breaks.
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Unread 02-09-2011, 02:34 PM   #10
350zmarty
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Well, I think I will go with the ole', " If it aint Broke, dont fix it" mentality. It runs great. I took it through emissions today, and with 153,000, it passed with flying colors
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Unread 02-09-2011, 05:59 PM   #11
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by 350zmarty View Post
Well, I think I will go with the ole', " If it aint Broke, dont fix it" mentality. It runs great.
Unless you are a trust fund child, that strategy is really the best.

I am a huge proponent of preventive maintenance with things like tuneup hardware, all fluids, cooling system components, belts, cleaning throttle body, etc.

But for the rest of the stuff, let her ride..............you'll generally get a bit of advance notice when things go south.

Gotta keep a keep eye and ear on all parts of your XJ.

And everyone should know where those gauge numbers should sit! Keep an eye on them!
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Unread 02-09-2011, 09:59 PM   #12
ratmonkey
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Quote:
Originally Posted by Azzy View Post
Thats because of the low tolerances. if the valve clearance was like that on some of the newer 4's and 6's... bam! Toast!
Its not close tolerance it is out right interference. The i6 won't contact a valve even at full lift I'd your break the chain. You have to break a valve spring or retainer for contact to happen.
An interference motor doesn't have that kind of open combustion chamber.
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Unread 02-09-2011, 11:48 PM   #13
diskman_1
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If you DO feel like replacing the timing set, make sure you call around first and verify that local stores have it. I was in the middle of my balancer/front cover problem a few weeks ago and NOBODY in town had a timing set for the 4.0. Out of at least 10 parts stores, it was a "special order" item.


I have 250K on my 92 and the chain is extremely loose. I just said screw it and put it together without a new set. Still runs fine.


Bonus video of my chain play.. lol



I also learned that a harmonic balancer puller WILL hose up the threads on your crankshaft so you get to purchase a tap and new bolt. I lucked out. Only lost the first 1/8 of my threads on the crank..
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Unread 02-10-2011, 11:35 AM   #14
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So, while I am replacing my PS system, radiator, water pump, and just about everything else on the front... might as well do this on a motor with 269K?
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