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Jeep Cherokee 4.0 engine question

Discussion in 'Uncategorized Threads' started by mark mckeehan, Mar 26, 2008.

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  1. mark mckeehan

    mark mckeehan TS Member

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    I have a 2004 Jeep Grand Cherokee with the 4.0 liter 6 cylinder engine. The vehicle has 80,000 miles. Oil has been changed every 3,000 to 3,500 miles. I went a little past 4,000 once or twice. Vehicle has been well maintained and never abused. The problem is, when it is first started in the morning, it has a loud knocking sound in the engine. It will do this for around 5 to 6 minutes until it warms up, and then the sound stops. I have noticed some noise since it was new, but it seems to have gotten worse in just the last few months. According to the gauge, it is holding excellent oil pressure at idle and during driving. I have always used 10w-30 Pennzoil and for the last year have used the High mileage Pennzoil. Is this anything to worry about or should I not be concerned. Thanks for any info and suggestions. Mark McKeehan
     
  2. hoggy

    hoggy TS Member

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    The knocking sound you are hearing is probably the lifters. The oil will drain out of them at night and they will produce a knocking sound until they pump back up with oil. It should not take 5 or 6 mins to do so. I doubt it would hurt any thing unless you are racing the engine before it goes away. Try revving your engine just a little to get them to pump up a bit sooner. You might try another brand of oil that adheres better.
     
  3. halfmile

    halfmile Well-Known Member

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    An experienced mechanic will be able to tell the difference.

    Lifters rattle.

    Serious parts knock.

    Have someone who works on these engines listen and give an opinion.

    Once you hear a connecting rod knocking, you never forget the sound. That's because4 of what happens next.

    HM
     
  4. miketmx

    miketmx Well-Known Member

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    I have owned Cherokees since 1987. I use synthetic oil in our 99. Our first one had an ignition miss that turned out to be the distributor was inserted one tooth in the gear out of alignment and the built in computer couldn't cope. That was an easy fix but it took a sharp service manager to read the tech bulletins on the problem.
     
  5. hoggy

    hoggy TS Member

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    Rod knocks don't disappear when warmed up. You are right that lifters do sound much different than rod knock and it's impossible to tell what the knock he's hearing really is without hearing for ones self. I never meant to imply NOT to have it checked out by an experianced mechanic. From how he descibed it I'm still betting/guessing lifters. Let us know Mark, I'm taking bets.
     
  6. Texas Ton

    Texas Ton TS Member

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    Probably a tight wristpin/piston pin. But you may also be hearing two different knocks, or this is different from the sound you heard when new.

    I'd say this new sound is probably carbon on top of the piston, try an upper cylinder cleaner, I would try to describe how to do this with water but it isn't for the squeamish or inexperienced.

    You DON'T need a high mileage oil, none do.
     
  7. geneleroy

    geneleroy TS Member

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    My 1999 Grand Cherokee Larado 4.0L purchased new, now has 170,000 miles, has always been dealer serviced at 3000 mile intervals using Mopar parts as recommended by Chrysler. My mechanic, working for Jeep for 29 years, says the 4.0L is the best overall engine he has seen. The only maintenance done to my engine was replacing the accessory drive belt. It didn't break, just replaced it as a precaution!

    Your noise sounds like a lifter problem, I'd leave it with your mechanic overnight so he can hear it first hand!
     
  8. birdtracker

    birdtracker Active Member

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    Mark: go to your local auto parts store such as NAPA, Advanced Auto Parts or Auto Zone. Ask for a bottle of "Lucas engine oil additive". Lucas makes additives for transmissons, power steering and fuel injectors also. It costs $10 here in Ohio. Add it to your oil at an oil change. Run for 5,000 miles. See if it helps. Usually 2 things create the noise you are talking about. The oil runs out of the lifters or the oil pump looses its prime. I am betting lifters. email me or pm here. Don
     
  9. chessney

    chessney TS Member

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    Mark, I have the same Jeep. I understand exactly what you are talking about. When you first start it, it sounds like a steel bar banging on in the block. When it warms up it is just a ticking noise. To put your mind at ease, Mine has been doing this for two years! At first I went out and got prices for used motors and figured I would just drive it till it blew. That was over two years ago and 20,000 miles later. Mine has 110,000 miles on it...Ziggy
     
  10. Quack Shot

    Quack Shot Active Member

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    Just picking nits, but if you are using 10W30 and the specs call for 5W30, you may have contributed to the problem if it's lifters or a similar issue. We had a fleet here that used 10W40 in everything and had lifter and cam problems in many of their vehicles. Changing to the specified weight did the trick for them. Use the oil that is recommended by the factory. Heavier oil can cause issues with teh newer, tighter clearanced engines.
     
  11. John Browning

    John Browning TS Member

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    Mark, the sound you hear is probaly a loose wrist pin , when the motor warms up it gets tighter, sound goes down. I do not think it will fail any time soon. I have a 96' with 220,000 or so on it, still runs good always used Castrol 10-30, and usally change when oil looks dark, about 6 to 7,000 miles. John
     
  12. code5coupe

    code5coupe Member

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    Loose wrist pins don't tighten up when the engine gets warm...if they are loose in the rod they stay the same, but it they are loose in the piston they get looser.

    I'm with halfmile: ticks (lifters, piston "slap") are minor ailments. Knocks (bearings) are to be considered serious.
    The Jeep 4.0L engine is generally thought to be pretty robust. Like chessney, you may be able to drive it for a long time before it goes blam. As long as the oil pressure is good, drive on.
     
  13. CalvinMD

    CalvinMD Well-Known Member

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    Some of the cheap oil filters have cheesey backflow check valves too...try a good name brand oil filter at the next change
     
  14. maclellan1911

    maclellan1911 TS Member

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    does this noise change pitch or frequency with engine speed? NUMBER: 25-001-03
    Check on this service TSB with your dealer. may maynot help?
     
  15. Big Jack

    Big Jack Well-Known Member

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    If you have an opportunity, check the oil pump pick-up in the pan. Pennzoil is a parafin base oil and I had one engine clog up the screen so tight, the oil pressure dropped. And that oil was changed every 3500 without fail.

    Big Jack
     
  16. chessney

    chessney TS Member

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    Mac: I dont know about Mark's but mine does not change pitch, but it knock faster with excelaration....Ziggy
     
  17. Salitorn

    Salitorn TS Member

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    I have a similar issue, start the jeep in the morning and I get the knocking sound but once the oil pressure gets up it goes away to a very low sound. I have to get out to hear it. I plan to take it into the shop soon to get it checked out, hopefully its what has been discussed here and doesn't take to much to get it taken care of.
     
  18. miketmx

    miketmx Well-Known Member

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    As others have stated my Jeep Cherokees with the 4.0 engine seem to run smoother and quieter with lighter weight oil. I had one with a gazillion miles on it but rather than use heavy oil I just added a can of STP Oil Treatment and it kept on trucking. I had a mechanic re-seal a leaking valve cover and that worked out OK where the Jeep dealers usually want to replace the valve cover but again this was an engine with a lot of miles.
     
  19. wm rike

    wm rike Member

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    It could be doom and gloom per all the previous postings, but being a positive kind of guy..

    My daughter had a Honda Civic with a bunch of miles, probably about a '90 model, that a chronic knock. It was horrible cold, and just bad once the engine was warmed up. The guy across the street does development work for Honda, so I asked him. He listend to it for about 5 seconds and said it was piston slap in the #2 and #3 cylinders. Honda tried to engineer it out, couldn't, and ultimately found out that it didn't have any demonstrable effect on engine life. He said to drive it and not worry about it.

    But that's a Honda. See what the Jeep guys say. They'll have the real skinny.
     
  20. The Jeep God

    The Jeep God TS Member

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    I have read alot on Jeeps and have extensive knowledge and experience with them and the cause of your noise could be a few different things. If it is a very loud knocking sound and then slowly subsides after a few minutes, it could be piston slap and as your engine warms the metals expand to fill the void...i.e. to much room for the piston. This is common among low and high mileage vehicles that Jeep made with the 4.0l engine except with high mileage vehicles it is usually do to carbon build up. If you think it is carbon buid up, then try putting in seafoam additive to your gas tank every other tank full and it will subside after a month or two. It is nothing to immediately worry about. The next thing is if it sound like a ticking/rattling noise, it could be the lifters. Jeeps are notorious for the lifters to tick when they are cold and when it warms up they subside except on higher mileage vehicles, this is do to hard driving and poor maintenance. If this is your case then try adding seafoam to your engine oil by following the directions on the can. The next problem could be the valve train. If adding seafoam to your gas tank and your engine oil does not fix this, then the only thing to make the sound go away is to rebuild the head or engine, BUT Jeeps are know for these problems and usually still run for many more miles like that. To me if it is a really loud knocking sound it is probably engine slap. Any questions feel free to e-mail me.
     
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