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Unread 12-04-2009, 06:45 PM   #1
SteveA1992
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2003 WJ 
 
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03 WJ 4.0 Engine Knocking

Over the past few weeks, i have noticed that there seemed to be a knocking sound coming from my engine. It does it pretty loud from a cold start and becomes less loud as the engine warms up. It never seems to completely go away. I have the 4.0 I6 in my 03 Grand Cherokee. I was just wondering if anyone else has experienced this with their engine and if i should worry about it. Also if anyone has any method that fixed this. One thing i was thinking of was using 5-30 in the winter instead of the 10-30 the engine calls for. Thanks. Any help greatly appreciated!!!

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Unread 12-04-2009, 11:55 PM   #2
mrtosh
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5w30 is better in winter conditions for cold starts period. The 4.0 is a notoriously loud motor. I've owned 5 XJ's all 4.0's. They've all had some sort of piston slap. Sounds a bit like a little diesel when cold. Hard to say w/out hearing for sure though. Any loss of power? Idle change? Video perhaps??
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Unread 12-05-2009, 12:00 AM   #3
gatorayde
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Mines had piston slap for at least 12k miles (only owned it since 131k, now has 143k on it). It's a 4.0 thing. Keep up on oil changes and listen to make sure it's not getting louder over time (guessing that your issue is piston slap or a lifter tap).
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Unread 12-05-2009, 12:09 PM   #4
JJAMISON_
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I just posted a response on another guys same sound thing. A friend of mine who is a mechanic said that it seems to be the lifters (i have a '04 WJ). Mine was doing/ is doing the same thing. He recommended Lucas oil treatment with every oil change. It really helps. I missed it during one of my routine changes and noticed the lifter ticking really bad. I hope this works for you. BTW, I substitute the Lucas for one quart of my oil during the change.
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Unread 12-05-2009, 12:42 PM   #5
mrtosh
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Lucas is a bandaid at best. It masks the issue. See how thick that stuff is when warm now imagine how thick it is cold and how hard you're oil pump is working to circulate that goo. On my 94 it actually caused a lifter to not get oil on a cold start and wore the lobe on the cam. It may be great for a motor on it last leg but that's it IMO. I'm fairly certain what the OP is hearing is piston slap. Lifters is more of a sharp "tick" than knock or slap...
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Unread 12-05-2009, 07:19 PM   #6
SteveA1992
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i was thinking with the 5-30 that the oil would be able to lubricate an area where the 10-30 cannot get to which may get rid of the sound. No loss of power or idle change
Mrtosh- nice ride
mrtosh- '01 XJ Sport: 4.0, AW4, D30 LP/C8.25, RE/RCX 5.5" lift, 33" BFG All-Terrains, RE SYE, CSF 3-core, Alabama cylinder head, ZJ HD fan clutch, Derale fan-mounted trans. cooler, Derale inline trans fan switch, B&M Trans. temp. gauge, Warn TC skid, Rugged Ridge D30 skid, Rustys steering brace, Aussie rear locker, some kind of QD's. -SOLD!
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Unread 12-05-2009, 08:34 PM   #7
Yardman Harry
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Here is a good thread. I have the same sound in my TJ, Im going to drop the oil pan in my next oil change to see if mine can be a really easy fix.

Here is the thread

http://www.jeepforum.com/forum/f9/4-...thread-700954/

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Unread 12-05-2009, 09:29 PM   #8
Rickyb
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Pour 1/3 of the pint of Seafoam in your oil, do 1/3 of it in vaccum hose, and the rest in your gas tank (pour in then fill up tank) your car will run crazy better.
A can of seafoam is about $10 at walmart or cheaper.
Buddies XJ was ticking real bad, we changed the oil to 5w-30 and seafoam'd the car and it runs and sounds so much better, but yeah the 4.0 is a LOUD motor, my girfriends friend has a old wagoneer's 4.0 sounds crazy loud like it has no cat or muffler.
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Unread 12-05-2009, 11:03 PM   #9
mrtosh
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Quote:
Originally Posted by SteveA1992 View Post
i was thinking with the 5-30 that the oil would be able to lubricate an area where the 10-30 cannot get to which may get rid of the sound. No loss of power or idle change
Mrtosh- nice ride
mrtosh- '01 XJ Sport: 4.0, AW4, D30 LP/C8.25, RE/RCX 5.5" lift, 33" BFG All-Terrains, RE SYE, CSF 3-core, Alabama cylinder head, ZJ HD fan clutch, Derale fan-mounted trans. cooler, Derale inline trans fan switch, B&M Trans. temp. gauge, Warn TC skid, Rugged Ridge D30 skid, Rustys steering brace, Aussie rear locker, some kind of QD's. -SOLD!
Thank ya. She was a money pit. After I changed the head on that one I could hear the lifters and the new valve springs as normal but the piston slap would be quite a bit louder than the two. It's a common thing w/the 4.0, something w/the sleeving on the cylinder and/or the wrist pins in the connecting rods/pistons. Naxja lists soooo many of these common issues.
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Unread 03-31-2010, 10:45 PM   #10
Hondaboy15
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I have a 1999 wj with a 4.0 and i pulled the motor (pain in the ***) cause it sounded like a rod was knockin (it was real loud) but when i took off the pan i noticed broken aluminum in the bottom of the pan, it was a broken piston skirt, all the way up to the bottom rings, it didnt leak oil or smoke but has some score marks on the cylinder walls. the rods seem to be fine, haven't completely torn it apart and done size checks on everything yet. ile deff. have to get it machined, was hoping just a simple hone, new rings rods, and bearins
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Unread 04-15-2010, 06:55 AM   #11
1bmfmdx
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Hello JF members, I'm new though I frequent Honda, Acura, and RC car forums.

My 02 WJ 4.0 Spec Edition has been making the dreaded noise for the past 20k. Similar symptoms, no major loss of power. Currently the Jeep has 88k total miles and I've decided to get rid of it. The noise began only a few months after the p/t warranty expired, go figure.

My buddy who has an older YJ wants to buy it for his wife. I told him I'd take $4k but would feel like **** if the engine tanked after he buys it. I know, its his risk, but they're barely making it and this will be their primary vehicle. He's actually selling one of his YJ's on Fleabay right now to pay me.

I am NOT mechanically inclined, a computer geek by trade. My mechanic told me 2 years ago it was piston slap. Last week he did the PA state insp/emissions, new tires, and told me the WJ was in great condition. Though he just shook his head over the noise and said he could make that go away but we didnt talk cost. He knows I dont want to put anymore $ into something I am getting rid of.

I assume when the piston finally goes, the cost would be quite a bit more than the piston repair. Any idea how much a shop would charge to fix the piston slap? Anyone else out there have a heart like mine? I would feel so horrible if they bought my WJ and the engine trashed shortly thereafter.
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Unread 04-15-2010, 05:54 PM   #12
Hondaboy15
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Change the pistons before they break in half! It's not that hard and when it does break it will at the least double your cost. A mechanic will charge you a fortune! Get a haynes book and do it yourself it's not all that hard I'm 15 and I'm doing all the work myself with my grandpa looking over my work occasionaly. Talk with someone that has rebuilt a motor before and they can help you. Dont remove the distributer, cam, timing chain or crankshaft. But put everything you do take off like the piston rods, lifters, and pushrods back the way it cam out. One of my pistons went at 120,000 after a bit of cold start pistonslap this is a 400$ fix if you do it yourself. Assuming the other motor parts are in good shape

Last edited by Hondaboy15; 04-15-2010 at 06:07 PM..
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Unread 04-16-2010, 05:54 AM   #13
1bmfmdx
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Thanks Hondaboy15, that was the same advice my mechanic gave me 2 years ago. I rolled the dice then and it lasted this long. Unfortunately, I don't have the time, space, or desire to take on a rebuild. I will sit down with my buddy and explain the risk to him. I guess I will knock another $2k off the price...geez, I should just give him the p.o.s.

Sorry everyone, I know you love your Jeeps...but 68k out of a motor never been off-road or abused is pathetic.
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