Odd Knocking/Rattling Sound - JeepForum.com
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post #1 of 10 Old 06-27-2020, 03:15 PM Thread Starter
Jeffreywp1
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Odd Knocking/Rattling Sound

This is my wife’s daily and I first heard the noise a week before taking it in for some exhaust work and assumed it was the exhaust. After getting back the noise is still there. The noise is only at low rpms at takeoff and is worse with ac on. I inspected the new exhaust very well and it is rock solid. Using my stethoscope I had my wife put it in gear and get it to make the noise and could not pin point anything. I tried the block front and back, the head, accessories, exhaust with the stethoscope and found nothing. The motor does not shift any when shifting in forward or reverse. Took it for a test drive on a hill from stopped and the noise cuts out at around 1300 rpms and even if I give it more gas with the brakes held firm the noise cuts out. Took a short video. The last two attempts are with the ac on.

https://share.icloud.com/photos/0tIg...X5s6w#Evington


Last edited by Jeffreywp1; 06-27-2020 at 03:40 PM. Reason: clarity
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post #2 of 10 Old 06-27-2020, 03:38 PM Thread Starter
Jeffreywp1
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Maybe this is a better way to attach the video?


https://mail.google.com/mail/u/0?ui=...=att&disp=safe
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post #3 of 10 Old 06-28-2020, 08:45 AM
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Check engine and trans mounts and look here.
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post #4 of 10 Old 06-28-2020, 01:36 PM Thread Starter
Jeffreywp1
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Broke out the stethoscope again this morning. Two things I find odd is that it does not make the noise at a cold start up. Also to produce the noise I have to put it in drive hold the brake and give just enough gas to rev up to 1000rpms with the ac on. If I turn the ac off the noise is cut by %90. I checked all the accessories and pullies again and found nothing and when I rechecked the engine block it seemed top be coming from there. That bummed me out so I quit thinking it was piston slap. Wouldn't piston slap be at its worse at a cold start?? Just went back out to double check it. I think I overreacted to the noise I heard this morning. The noise on the block at free idle without the odd knocking sound is the same with it under load with the ac on while knocking. Then I checked the right engine mount and it seemed to come from there even though there is no free movement at the mount. Could the engine mount be the issue even though there is no play??
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post #5 of 10 Old 06-28-2020, 04:18 PM
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Did you check what Cruiser posted?

1995 Jeep Cherokee Country 4X4 Stock
AW4/NP231/C8.25/D30/"UpCounty" suspension
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post #6 of 10 Old 06-29-2020, 07:12 AM Thread Starter
Jeffreywp1
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I did check the mounts in the beginning to make sure there was no play(visible). After hearing the noise at the right motor mount with the stethoscope yesterday evening I was very happy after thinking it was piston slap all day long. Took a peek before work this morning I saw that I am missing one bolt to the right mount bracket. The hardest one to get to it seems. I am hoping that it came loose and fell out and is not broke off. Does anyone know off hand what size it is.
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post #7 of 10 Old 07-11-2020, 03:07 PM Thread Starter
Jeffreywp1
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After getting under the car I could see that the bolt was broken off. I replaced the other two with 1.25 inch bolts with flat and lock washer making them roughly 1/16 inch shorter than the originals. It still rattles a little and I don't think the center bolt is tight and is bottomed out. The only way I see myself getting the broken bolt out is to take the mount and the mount bracket that is attached to the frame rail off. Does the frame rail motor mount bracket come off easy?
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post #8 of 10 Old 07-15-2020, 03:58 PM Thread Starter
Jeffreywp1
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While I am sure that there was some rumbling coming from the motor mount before I changed the two bolts out, the noise that I have been chasing was coming form the flex plate. Three of the four bolts where loose, now all is quiet. Still need to replace the broken motor mount bolt.
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Last edited by Jeffreywp1; 07-15-2020 at 03:59 PM. Reason: clarity
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post #9 of 10 Old 07-15-2020, 05:59 PM
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Please remember Jeep engineers spend large amounts of time and ingenuity creating those rumblings. They get bonus' based on how many years they can delay their appearence.
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post #10 of 10 Old 07-17-2020, 07:16 PM
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Quote:
Originally Posted by Jeffreywp1 View Post
While I am sure that there was some rumbling coming from the motor mount before I changed the two bolts out, the noise that I have been chasing was coming form the flex plate. Three of the four bolts where loose, now all is quiet. Still need to replace the broken motor mount bolt.
I was wondering about the flexplate bolts. Good job of tracking it down!!!

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