PM # 17: check your exhaust system cushions

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Been discussed in the past and just recently so thought I'd post this up for those that haven't seen it yet.

My 97 model FZJ80 recently started getting a new vibration for example while idling in drive, foot on brake, more apparent when the engine idled up with the AC compressor coming on or just increasing the rpms with the accelerator pedal. Also it became more apparent on acceleration from a stop. This vibration/rumble got progressively worse over the course of a month or so to become aggravating enough I decided to get down under the vehicle check things out.

When I looked, shook, and pushed up on the exhaust system to check for looseness, broken hangers etc, and found deteriorated exhaust hanger cushions. The photos tell the story:


First photo shows the #3 hanger position (97 FZJ80) at rear of muffler. Notice how the upper and lower hanger brackets are offset. They should be directly in line with each other if the cushion was intact. Photo taken from the rear looking forward:

FZJ80 Exhaust cushion cracked.png



Look closely and compare the two photos: this next one shows how the gap increased while pushing up on the muffler/pipes. This indicates the cushion has come apart.

The two center rubber blocks should be in-line with each other but not touching and the side sections should be intact. Note that one side has separated from it's plate and the other side is partly missing:

FZJ80 Exhaust cushion cracked pushed up to show gap.png



Example of a new exhaust system cushion (17567-17010) for comparison. You'll need three of the same cushion if replacing all of them (FZJ80). Check the parts diagram for your model to confirm.

FZJ80 exhaust system cushion new cropped image.jpg


(tip: you may want to replace the four nuts (90179-06007) for each new cushion)


This next photo is of the front exhaust system cushion (#2 position 97 FZJ80) showing a side view of that cushion which has also come apart with one section closest to the camera missing. Photo taken from the front looking toward the rear:

FZJ80 Front exhaust cushion collapsed.png




Next photo was taken while pushing up on the exhaust pipe, note the increased gap between the upper and lower pieces:

FZJ80 front exhaust cushion showing gap.png




Main take away point: there should be zero gap in the cushion when pressing up on the exhaust system. If there's any gap or independent movement between the top and bottom of the cushion/brackets it means the cushion has failed and needs replacing. Not sure yet if that's the cause of all the vibration I've been getting, will know more once the cushions are replaced.


ps: 99% of the orange splatter in the photos is just red clay, not rust
 
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Joined
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Here's a photo of the third exhaust cushion (FZJ80) found at the rearmost exhaust bracket at the resonator (click photo twice to magnify). It also appears to have collapsed.

FZJ80 exhaust cushion #4 rearmost position at resonator.jpg
 
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Do you have a shiny part on your muffler near the drive shaft? I changed mine a few months ago when i found that someone wanted to save 11 dollars and use zip ties in place of replace those pads... Well i replaced mine and all is well but if i had not found it sooner i would have worn a hole in my muffler corner with the drive shaft.
 
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Glad you found the shade tree mod before anything happened.
 
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ps: 99% of the orange splatter in the photos is just red clay, not rust

99%? j/k thanks for the tip. I'll check mine as mine is like 98% rust and 2% clay and I do have some slight rattling!
 
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Part number (90179-06007) for the nuts (4 per cushion) added to original post.
 
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I go through those stupid cushions on what seems like a yearly basis! If you ever hear any strange noises or vibrations on your car, look at these things first!

I don't know what the go is with my 80, but it just eats exhaust components. It's always an easy fix and it could be worse but I always seem to have problems with the exhaust cushions, mounts and welds. I do a lot of 4wding so maybe the flexing is killing them.

Last time I bought a cushion I bought 4 and keep one in the car at all times as a spare.
 
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I've searched in the past for an upgraded replacement cushion but have been unable to find one made out of polyurethane with a Durometer similar to rubber.
 
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LandLocked93

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The very last cushion on mine, just ahead of the resonator - which is just ahead of the end of the pipe - was shot.
Ended up using a rubber foot (donut?) off the bottom of a pancake air compressor, ~3" in diameter and about 1" thick. It is attached to the top plate of the previous cushion, and secured thru an existing hole with a bolt.
I realize the pipe should be fixed in place with the cushions, but this just rests atop the bottom bracket of the previously existing cushion.
It was a temp fix at the time (3yrs ago or so) but have found that the ability of the exhaust pipe move vertically has helped to save it during the several times I've ended up coming down on something in that area.
And instead of the pipe being fixed in place and risking damage, it moved up and over the obstacle (usually branches from felled trees, a rock or two, etc).
Very good PM items to track the condition of. 👍

edit:and actually in the area of the cushion I'm referring to, there is a 'tuned weight' to help with vibrations. If that is missing, there will be incurable gyrations that may or may not bug the average user.
 
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Got photos of the fix??
 
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There are actually three of the same cushion (#2, #3, and #4 exhaust system positions) for a FZJ80. The third cushion is located at the bracket for the resonator.
 
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There are actually three of the same cushion (#2, #3, and #4 exhaust system positions) for a FZJ80. The third cushion is located at the bracket for the resonator.
Good point. The one near the resonator looks great, so I'm thinking, hey, I'm rocking. Then, I went and looked at the muffler cushions. YIKES!!!
Oh well. Compared to my complete engine rebuild, this was a 99 banana job:banana:
:clap::wrench::beer:
 

cartercd

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As your exhaust system gets beat up over time, the mounts on the exhaust no longer align exactly to the frame mounts, which puts those rubber cushions in a constant state of tension. Some of them won't last long. You used to be able to by Bosal part number 255-726 for cheap, but they appear to be out off stock everywhere. On my most stubborn mount I bough a universal exhaust hanger similar to below, cut the reinforced rubber into strips, and then used that rubber as the cushion between the fame and exhaust. It has held up very well.



1665293745438.png
 
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I found the same situation with my exhaust, the two replacement cushions (one in front and the other at the rear of the muffler) after installation are under tension with the rubber core being bent maybe 1/4" or so out of line comparing the top to the bottom.

One solution I've considered is to remove the frame mounted brackets and make a longer oval hole cut in the frame bracket to give some leeway so the studs of the cushion can move to a neutral position (no torque on the rubber core) before tightening up the nuts. Looks like there's enough room on the bracket for elongated oval stud holes.
 
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surfpig

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Here. Now.
I go through those stupid cushions on what seems like a yearly basis! If you ever hear any strange noises or vibrations on your car, look at these things first!

I don't know what the go is with my 80, but it just eats exhaust components. It's always an easy fix and it could be worse but I always seem to have problems with the exhaust cushions, mounts and welds. I do a lot of 4wding so maybe the flexing is killing them.

Last time I bought a cushion I bought 4 and keep one in the car at all times as a spare.
I keep a number of spare cushions on hand as well.
As your exhaust system gets beat up over time, the mounts on the exhaust no longer align exactly to the frame mounts, which puts those rubber cushions in a constant state of tension. Some of them won't last long. You used to be able to by Bosal part number 255-726 for cheap, but they appear to be out off stock everywhere. On my most stubborn mount I bough a universal exhaust hanger similar to below, cut the reinforced rubber into strips, and then used that rubber as the cushion between the fame and exhaust. It has held up very well.



View attachment 3135611
This is also what I have where the rearmost cushion used to be. Works OK.
 
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After my last Rubicon trip my exhaust was pretty much sitting on the rear crossmember. The under the frame exhaust is a rock magnet.

I now keep a couple of these in the truck.
 

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