Help with a knocking noise
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Joined: Apr 2008
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Help with a knocking noise
I'm looking for some help figuring out a noise my jeep has been making since February. Attached is a video to listen. The flexplate bolts are tight with red lock-tite so it's not that. The noise is there in every gear including neutral and it gets drowned out as rpms increase. Once the motor is fully warmed up to 210 its goes away. I ran it with no belt and its still there, so I don't think it's pulley related. I drained the oil once and everything looked fine. It seems like its loudest near the bottom of the oil pan / tranny bellhousing. Any help would be appreciated. Thanks.
Member
Joined: Nov 2011
Posts: 150
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From: Pensacola Fl
Year: 2000
Model: Cherokee
Engine: 4.0
I would really like to know what this is so I can get it fixed asap so please anybody with any serious suggestions don't be shy..and im not try to steal your thread OP im just experiencing the same exact thing
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CF Veteran
Joined: Mar 2011
Posts: 1,102
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From: Waterloo, Iowa
Year: 2000
Model: Cherokee
Engine: 4.0
I would have to say it's piston slap since it goes away when the vehicle warms up (piston expands). Mine does the same thing. 
It's very common with the 4.0's.
It's very common with the 4.0's.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Ball bearings in a blender?
Funny! The cat runs out from under the Jeep when I start it. So I hooked your video to the house speakers......there is almost a kiddy imprint in the condensation on my glass front door!
I'd go with piston slap. I doubt all (or most) of the rods are clearanced and when the oil warms up it gets better.
I'd think to have that clearance between piston and bore you would have some pretty high miles. Normally 50* is cold here, freezing is rare so I get away with running Castrol 30W (love it Btw). Not recommending that, but you might try some Rotilla 15-40 if you have high miles. Affordable at Wall Mart, and heck, it does sound like a diesel! It may, or may not, help cushion whatever is bashing around in there.
I'd go with piston slap. I doubt all (or most) of the rods are clearanced and when the oil warms up it gets better.
I'd think to have that clearance between piston and bore you would have some pretty high miles. Normally 50* is cold here, freezing is rare so I get away with running Castrol 30W (love it Btw). Not recommending that, but you might try some Rotilla 15-40 if you have high miles. Affordable at Wall Mart, and heck, it does sound like a diesel! It may, or may not, help cushion whatever is bashing around in there.
Last edited by DFlintstone; Mar 21, 2012 at 09:54 AM. Reason: + Jeep
Member
Joined: Nov 2011
Posts: 150
Likes: 0
From: Pensacola Fl
Year: 2000
Model: Cherokee
Engine: 4.0
Originally Posted by DFlintstone
Funny! The cat runs out from under the car when I start it. So I hooked your video to the house speakers......there is almost a kiddy imprint in the condensation on my glass front door!
I'd go with piston slap. I doubt all (or most) of the rods are clearanced and when the oil warms up it gets better.
I'd think to have that clearance between piston and bore you would have some pretty high miles. Normally 50* is cold here, freezing is rare so I get away with running Castrol 30W (love it Btw). Not recommending that, but you might try some Rotilla 15-40 if you have high miles. Affordable at Wall Mart, and heck, it does sound like a diesel! It may, or may not, help cushion whatever is bashing around in there.
I'd go with piston slap. I doubt all (or most) of the rods are clearanced and when the oil warms up it gets better.
I'd think to have that clearance between piston and bore you would have some pretty high miles. Normally 50* is cold here, freezing is rare so I get away with running Castrol 30W (love it Btw). Not recommending that, but you might try some Rotilla 15-40 if you have high miles. Affordable at Wall Mart, and heck, it does sound like a diesel! It may, or may not, help cushion whatever is bashing around in there.
CF Veteran
Joined: Aug 2010
Posts: 1,168
Likes: 4
From: Williamsport, Pa
Year: 1997
Model: Cherokee
Engine: 4.0L
I know you said the flexplate bolts are tight, but maybe there is still a slight chance that the flexplate is cracked- usually happens near the bolts that hold it to the crank, which you can not see or get to unless you remove the tranny.
Senior Member
Joined: Jun 2010
Posts: 524
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From: austin texas
Year: 1998
Model: Cherokee
Engine: 4.0
my 1998 has the same noise its not very loud but its noticeable, oil psi warm is 22psi idle 50psi max and 40 cruising. It has 175,000 miles i figure its a spun bearing or something im just going to drive it tell it throws a rod out of the block then get a Junk yard motor. Good luck let me know if you figure out what it is.