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98 4.0 Rattling sound coming from engine bay

D

dishner

NAXJA Forum User
Location
North Carolina
I have a 1998 Manual Cherokee with 170,000 miles on it. There is a rattling sound that I would liken to a bolt boucing aroud inside of a thick metal container. When I'm driving it sounds like it's right at my feet. It ONLY does it under a load, like high speed or pulling a load. Absolutley will not do it at idle, which is making it very hard to pinpoint. No matter how high I rev it at idle it never does it. Only when the tranny is engaged. I suppose that leads me to believe it is in the transmission. Any ideas?

Thanks.
 
Maybe the bolts have worked loose on the flexplate??? It's a common problem and results in a knocking sound. Do a search on flexplate and there should be write-ups on how to tighten the bolts through the access cover. Just a thought....
 
HMmmmm--glazed!

That is how the CAT cone on my FS Bronco was bouncing around inside the CAT housing.

Try thumping on the CAT with a rubber/plastic mallet and listen for any weird sounds.

Another thing--less likely based on your guestimate of the where the sound is coming from--but take a look at your harmonic balancer. When the rubber separates it can start making contact with the timing cover.

Good luck.
 
I think If Joe told you to check those 2 items, you had better listen to him & recheck them again. He is about 9 out of 10 right on his answers. And yes, you don't have a flexplate, but loose flywheel-crank bolts or loose pressure plate bolts can create a thrown rod noise under a load.
 
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i would inspect the engine and transmission mounts. I have a rattle sound coming from my xj because the transmission mounts and exhaust mount/hanger are not good and the exhaust pipe sometime rattles against a metal surface.
 
DISHNER i drive a 98 have much the same problem and if its like mine (i have 174000 miles on mine)..... It's probably the exhaust pipe, it's laying on your cross member. Go down there with a bar of some sort and pry the thing upwards hard... noise will go away (for a month or so then it will come back just go back down and bend it up again).... For the longest time i thought it was more serious but it aint ;- )

post back after you try this!
 
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skylinergtr said:
i would inspect the engine and transmission mounts. I have a rattle sound coming from my xj because the transmission mounts and exhaust mount/hanger are not good and the exhaust pipe sometime rattles against a metal surface.
Click to expand...
If it is not what Joe said, I'd bet on this.

Another thing you can try - put the rear axle on jackstands, preferably 6 ton or larger ones (they have a larger footprint and axle cradle and are thus harder to knock over), chock the front wheels solidly, verify it is in rear wheel drive (perhaps even disconnect front driveshaft if you are truly paranoid or have bad luck), then have a trusted helper get in and throttle it up while standing on the brakes. From the side of the vehicle, see if you can pinpoint where the sound is coming from.
 
Thanks for the replies fellas. I've been away from the Jeep for a few days recovering from a surgey. I'm gonna mess with it tomorrow. I'll let you know what I find.
BTW, the reason I think it's not the CAT is because I gutted it 5 years ago. I crawled under it and whacked it with a hammer and could not reproduce the sound. Thanks again.
 
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I have a five speed as well, and my rattling sound comes from the t case shift lever. Next time you hear it, press down on the lever and see if the noise stops....
 
SqueegieSteve said:
DISHNER i drive a 98 have much the same problem and if its like mine (i have 174000 miles on mine)..... It's probably the exhaust pipe, it's laying on your cross member. Go down there with a bar of some sort and pry the thing upwards hard... noise will go away (for a month or so then it will come back just go back down and bend it up again).... For the longest time i thought it was more serious but it aint ;- )

post back after you try this!
Click to expand...

My 98 also had the issue with the exhaust hitting the crossmember. On mine the rubber support that held the exhaust up disentigrated. That was a pain to replace, no one had a repacement option, i had to ghetto fab a new mount.
At the time i had around 165k miles.
 
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