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View Full Version : Knock, rattle, pop?



Mudderoy
09-15-2014, 09:18 AM
I recently notice a knocking noise while at idle. I thought it was the transfer case tapping on the freshly reinstall skid, but no.

It would come and go. Above idle you wouldn't hear it and it would only return sometimes, usually when the engine wasn't at operating temperature.

I figured I better find the cause A.S.A.P. before it found me to or from work.

After pulling the 98 into the garage, I grabbed sockets and socket wrench to remove the inspection plate so I could check the flex plate torque converter bolts. I've never heard lose bolts make this much noise but it was an easy first thing to check. Hell maybe one fell out that the nut was jammed in there somewhere.

After removing the inspection plate I notice this...

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Well that's not right. I don't know if you recognize it but that's the factory upper control arm bolt.

It wasn't until I was able to get it out that I realized the nut didn't vibrate off the bolt SHEARED off!

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Two things I noticed recently. The passenger's side wheel felt like it was folding over during sharp left turns, and didn't want to center itself.

I was able to find a grade 8 bolt and get it back together after much effort and a tie down ratchet strap, no destroyed.

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I returned to the flex plate bolts. All but one was locked down tight. The loose one I wouldn't call loose I was just able to turn it slightly.

I didn't hold out much hope that either of these "fixes" were the solution to my popping/knocking problem.

I started up the engine and with the wheels chocked from forward and reverse I crawled under the jeep to find that noise.

I thought maybe it was the down pipe rattling on the cross member. I took my big screwdriver and used it to move the down pipe off the cross member, strangely the knocking changed. I tried just jamming the screwdriver in between the down pipe and holding it still, the knocking came back. It only changed when I put pressure, leverage up on the pipe.

I moved to the collector to see if the two bolts were in, everything was solid. I was able to apply pressure to the exhaust further up and the knocking would stop.

Then I saw this...

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If you can't make it out, or tell where it is, this is the transmission to engine block bolt, driver's side. It was completely out of the block and the only reason it was there was the kick down cable bracket for the transmission was there.

I had to remove the kick down bracket to tighten up this bolt.

I thought if one wasn't tight maybe more, so I started checking. Looking on the passenger's side I saw that directly across from the loose bolt was a hole, but no bolt! Digging through my "spare" Jeep bolts I found one long enough to fit. Tighten it down.

Put everything back together, inspection plate, kick down bracket, and started it up.

No knock.

Drove her to work this morning. No more wandering on those "lines" that separate the two road surfaces. "Expansion/contraction" joints? Oh and no knocking.

Funny thing is I noticed the bushing on the pass side UCA was coming apart maybe a month ago, but the bolt was still in there. It's not unusual for me to drive 80 mph and well, I'm just glad it held together.

Inspect your rigs, regularly.

Rlpetty43
09-15-2014, 09:41 AM
Never hurts to get under the rig and linger for a bit good reminder and glad you caught that. Not long ago I had several loose lug nuts from just randomly pulling a tire off

4.3LXJ
09-15-2014, 10:10 AM
I find stupid stuff like that too occasionally.

bluedragon436
09-15-2014, 11:42 AM
I went through and climbed under my old 98 multiple times to check for anything out of the ordinary, and usually always tried to hit all the bolts that had been pulled for the lift install each time just to makes sure they were still snug.. Glad that you were able to take care of that knocking sound, and def that you found that bolt in the process before the arm fell out, and you had more then just some wandering going on while doing 80 to work..

Mudderoy
09-15-2014, 11:47 AM
I went through and climbed under my old 98 multiple times to check for anything out of the ordinary, and usually always tried to hit all the bolts that had been pulled for the lift install each time just to makes sure they were still snug.. Glad that you were able to take care of that knocking sound, and def that you found that bolt in the process before the arm fell out, and you had more then just some wandering going on while doing 80 to work..

I wonder if I over tightened the UCA bolt and started twisting it. At any rate I'm going to get another grade 8 bolt for the other side.

bluedragon436
09-15-2014, 11:53 AM
You have upgraded your upper and lower arms right?? If so, I'd just go ahead and replace them all, that way you will have peace of mind that the others won't have similar failures...

XJ Wheeler
09-15-2014, 04:45 PM
This is one of the reasons it great to do your own work. You notice stuff like this. Glad you found all that! If those trans bolts slip out again might want to put some locktight on em.

Sent via messenger pigeon - i talk, he types.

Brasscatz
09-15-2014, 07:19 PM
Nice catch....yikes

Mudderoy
09-16-2014, 04:34 PM
I have a theory, based partially on observation...

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The popping has left the building and the Jeep, now just have the ticking noise.

If the transmission not being butt up against the block was causing the popping noise, why?

I'm thinking cracked flex plate. I now have a slight vibration that wasn't there during acceleration.