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2001 Front end popping / rattle ... but not all the time.

Redsnake

NAXJA Forum User
Location
Tulsa, OK
OK so I've read thru all the 'front / popping / rattling' threads I can find but I still can't seem to find the issue I'm having.

The front left/drivers side of my '01 XJ has a rattle or popping that comes from what feels like the front drivers side ... sometimes it feels like it's right under my feet. Here's the strange part. I don't have this pop in the morning while driving into work but on the way home I notice it almost every time I roll to a stop. It only happens when I'm coming to a stop (or that's when it's most audible and I can feel it in my feet). It doesn't do it when I drive over a bump in the road, it doesn't do it when I'm turning and seems to be only present when under 10 mph and up until I stop.

Things I have checked: Track bar bolts have all been tightened down w/my impact or breaker bar to assure they're tight. I have Black Magic front brakes w/ Centric rotors (~ 2 years old) and when I did those the caliper bolts were greased and there were no apparent grooves where the pads ride. I've visually checked and can't find any cracks or broken bolts. Running Brown Dog Motor Mounts and a fresh Auto Tranny Mount. I replaced the OE XJ tie rod w/one from a Grand Cherokee ~ 1.5 years back and it looks good. I also think I've replace both front Hub Assemblies (can't remember for sure as I've replaced them on both my boys vehicles and all 3 XJ's & Dodge Ram we've had in our family rotation over the past few years... seems like a VERY common issue on 4x4's with over 100K miles). Replaced Sway Bar & end link bushings w/ Energy Suspension bushings.

Things I haven't checked but look ok: Power Steering spacer / bracket (the Aluminum one that fits between the gears and frame rail that tends to crack), Control Arm bushings (they look ok but I know that's not always the case). I have KYB shocks on the front that were installed ~ 3 years back so perhaps those could have gone bad... (I haven't pulled the shock off to check rebound and it doesn't appear that any shock oil is leaking). Haven't pulled the front driveshaft off to see if the noise is gone... simply because the noise isn't there all the time.

My XJ has 162K miles on the odometer and any tips or things to check would be appreciated. I hate to just throw parts at my rig to try and solve issues.

On the want to add list is the BoostWerks's steering brace, JCR steel steering box spacer, New front Lower and Upper Control arms ... although I'm not sure when those will be in the budget. Thanks for any suggestions and tips. Hopefully I'll have a chance to check this out over the weekend.
 
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check to make sure the exhaust isnt hitting anything.

Hmmm... hadn't thought of that. I did replace the Header and Pre-Cat exhaust this past Fall and have been experiencing an exhaust leak that needs to be tracked down... could be something is rattling on the exhaust as it gets up to Operating temps.
 
It sounds like CA bushings to me! How much lift/what arms?
 
It sounds like CA bushings to me! How much lift/what arms?

I've been thinking the same thing... No Lift and still running the OE Upper and Lower Control arms as far as I know. I'm not the original owner and got it with ~ 92K miles from a used dealership.

Would you think Upper or Lower CA bushings... or perhaps both?
 
It sounds like CA bushings to me!

Considering the rubber bushings are 16 years old with 92k, a bad CA is definitely on the list of things to check.
The three times i've encounter this problem, it was a worn or loose UCA.

Pulling the CAs, for inspection or replacement, isn't that hard, as long as you only remove one CA at a time.
I keep a come-a-long handy, in case the axle needs to be nudged forward or backwards a bit. It's a useful tool for the solo mechanic.
 
Thanks for the info guys!! I had a very busy weekend so I wasn't able to mess w/my XJ. Also, new Control Arms have been on my 'to-do' list for a while just because I wanted to add some clearance for wider tires, but this gives me an excuse.

To add another question for this topic... would it be OK to change just the Lower Control Arms or is it much better to swap in new Upper and Lower Control arms at the same time?
 
Many of us have slowly modified the suspension. Adding either upper or lower is OK, both is better. I first changed the LCA to allow for wider tires.
As the lift increase, the UCAs were changed, to better adjust the alignment and wheelbase.
 
Thanks again... now the 'what to buy' and 'which is the right LCA for me' comes into play. I've been looking at Core4x4, Ironrockoffroad, JKS and Metalcloak...

I do almost no offroading in my '01 XJ currently so I don't need the absolute best, but if I'm going to spend say $200 on a set of LCA's... why not spend an additional $50-$100 to get something that much better. Decisions Decisions Decisions...
 
So I was able to swap in some Teraflex Monster LCA's this past weekend and while they are beefy and this helped tighten up the feel of the jeep there's still that rattle / pop noise as before. I'm still on the hunt to fix it up but the LCA's were apparently not the culprit here.

I think my next thing to check is the steering box spacer and then look a bit closer for any frame cracks (which I've not been able to find) ... perhaps it could be my brake pads rattling but since I have Black Magic pads and centric rotors, I'd hope that's not my issue.

Here's the LCA's...
 
Inner fender Hasta

Are you saying this subject is like beating a dead horse and has been asked/answered many times before? I'm not sure I've ever heard that the inner fender can cause rattling / popping... but I'd like to hear more if this is the cause so I can fix it.
 
One thing that will cause a popping noise (though unlikely on a stock-ish rig) is the spot welds failing on the inside lower control arm bracket(s). There is a gusset that is spot welded to the frame rail that runs at an angle down to the mount. These welds can pull out taking some of the frame with them. They can also Crack where they are bent at an angle next to where they are attached.

For me that was the initial point of failure for the entire bracket. I've wheeled my rig pretty hard at times over the years so it wasn't too terribly surprising. I wouldn't think that it would be a problem a rig that sees only street and light trail use only.
 
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Inner fender Hasta

Odd response to a subject I can't remember seeing before over the last 13 years.
What part of the inner fender can make a popping noise and how do you fix it?
 
Update: Sorry I never got back to updating this post...

As it turns out, my Brown Dog Rubber Motor Mounts had taken a dump... the rubber was shot. Not quite as bad as the OE Rubber mounts do but they were bad enough. I replaced them w/ a pair of StinkyFabRacing (SFR) mounts and the rattles went away. I only found out by chance as the SFR mounts were bought to aid in the NHV that the BD Mounts had always caused. After replacing the Motor Mounts I've not had the rattle that has been pestering me for a while. Hopefully down the road this thread might help someone else.
 
Update2:

So after ~ 6 months of use the SFR mounts are also now causing severe NHV and it's driving me crazy!! It's possible that it could be something else causing this but right now I'm thinking about just ordering a set of OE Engine and Transmission Mounts and seeing where that gets me. The vibration is SO annoying... it's caused the upper part of my dash (over gauges) to split apart and rattles like crazy when sitting at a stop light or while idling in a parking lot. Door panels, dash panels and even my interior fuse panel popped off the other day because of the shaking and rattling. I'm wondering if something else might be the culprit but everything on my suspension and mount bolts seem tight and/or snug. Ugh... If not for the feeling of driving a giant vibrator I'd love my XJ. :)
 
i had a similar problem, drove me nuts for a long time, went through 2 sets of motor mounts, turned out my transmission crossmember was installed backwards.
 
Your transmission crossmember was backwards? How did you figure that out?? 🤔

after my 2nd set of motor mounts i called brown dog to try their set, the person i talked to on the phone suggested i look at the crossmember, there is a direction that the slots face, i cant remember off hand, but sure enough mine was in backwards. also make sure you replace your transmission mount when you do your motor mounts, if 1 mount is bad the other 2 are bad, or are going bad.

also i had an occasional popping sound in mine, turned out my front driveshaft would hit my front O2 sensor under load, fixing the crossmember fixed that as well.
 
after my 2nd set of motor mounts i called brown dog to try their set, the person i talked to on the phone suggested i look at the crossmember, there is a direction that the slots face, i cant remember off hand, but sure enough mine was in backwards. also make sure you replace your transmission mount when you do your motor mounts, if 1 mount is bad the other 2 are bad, or are going bad.

also i had an occasional popping sound in mine, turned out my front driveshaft would hit my front O2 sensor under load, fixing the crossmember fixed that as well.

Thanks for the follow-up. I was under the impression the crossmember was pretty much the same left and right but obviously not the same top/bottom. I'll have to see if I can find some pics and compare to how mine is mounted. I'm not the original owner so could be it's been backwards since I purchased it years back.

I did replace both motor mounts and the transmission mount from SFR. High quality parts but nothing I've tried have kept the NHV at bay like genuine OE Rubber mounts. I've tried MORE Rubber, Brown Dog Rubber and now the SFR Mounts. They are all high quality but for a 99% daily driver that will never see rocks or hard offroading I'm not sure it's worth it for me. Granted the OE can and do wear out faster, but even my Brown Dog mounts wore plain out after about 3-4 years of DD'ing.
 
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