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knock in bottom end 4.0L?

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Old 09-14-2007, 06:39 AM   #1
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Default knock in bottom end 4.0L?

i have a 97 xj and it has 160k on it and started making a knock coming from the bottom end i checked the rod caps and every thing seems to be tight in their so if its not a rod bearing what can it be?
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Old 09-14-2007, 12:06 PM   #2
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where exactly does it sound like its coming from if your sitting in your jeep. if its at an idol try pulling up a bit on your transfer case shifter and seeing if that helps. often enough the linkage gromets get worn out and it makes a nocking noise that sounds a lot like the engine.

-Kyle
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Old 09-14-2007, 09:14 PM   #3
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ill try that cause it seems to be coming from the back of the motor
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Old 09-14-2007, 10:01 PM   #4
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ill try that cause it seems to be coming from the back of the motor
yup same exact things happens to me.

-Kyle
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Old 09-15-2007, 09:24 AM   #5
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Well, I pulled up on the shifter and it still makes the noise. Do you have anymore advice I can try? But I reallly do appreciate you help.
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Old 09-17-2007, 12:58 PM   #6
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when i got my jeep it had a bad knocking noise towards the rear of the engine.

ive had myself and a number of mechanics diagnose it as an engine knock.

so i got a rebuilt engine and had it installed, and while putting it in we found a cracked flywheel. replaced flywheel= no more knocking.


it was a faint hairline crack, difficult to see by removing the dust shield. but its a fairly common occurence on the cherokee's. that faint crack caused the most horrible noise.
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Old 09-17-2007, 01:03 PM   #7
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i forgot to ask if this goes away as your engine warms up.

-Kyle
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Old 09-18-2007, 10:04 AM   #8
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i forgot to ask if this goes away as your engine warms up.

-Kyle
it does it all the time even warm.
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Old 10-04-2008, 04:59 PM   #9
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Quote:
Originally Posted by ktmracer419 View Post
when i got my jeep it had a bad knocking noise towards the rear of the engine.

ive had myself and a number of mechanics diagnose it as an engine knock.

so i got a rebuilt engine and had it installed, and while putting it in we found a cracked flywheel. replaced flywheel= no more knocking.


it was a faint hairline crack, difficult to see by removing the dust shield. but its a fairly common occurence on the cherokee's. that faint crack caused the most horrible noise.
hey there i have had rod knocks in cars in the past and they always have two things in common. the knocking sound is constant through the range of rpms, it never goes away, and you can always hear metal hitting metal. well i have got what sound like more of a thudding but at a constant speed, and it will go away at certian rpms. I cannot for the life of me figure out what it is, is this what your flywheel acted like.? please let me know, thanks so much.
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Old 10-04-2008, 10:58 PM   #10
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Does anyone sell a better quality flywheel for the 4.0? My 98 is doing the same thing...also a friend at work with a 94 sounds exactly like mine...
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Old 10-04-2008, 11:00 PM   #11
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I had a knocking sound in 4.0l... sounded like something trying to punch a hole in the oil pan at times. Mostly sounded like someone rapping on the oil pan with a hammer. Turned out it was the harmonic balancer was bad.
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Old 10-04-2008, 11:08 PM   #12
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Had a cracked flexplate on a '92 do that same thing. I pulled the engine to rebuild it and fould the cracks in the flexplate and got another one. Put that same engine back in without so much as an oil change and no more knock.
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Old 10-05-2008, 09:10 AM   #13
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You can check the flexplate bolts and for cracks by taking the lower dust shield off but you have to take the starter off first. If the bolts are lose use some locktite on them. If they are not, then inspect for cracks if none then replace harmonic balancer.
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Old 02-22-2011, 05:38 PM   #14
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how do you find out if the balancer is bad? it knocks just a little bit, and it sounds like someone is taking a soft faced hammer to the pan.
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