Bad front upper shock mount (short close-up video)?

[Lindenwood]

I have been trying to track down a heavy rattling clunk and found this. I previously experienced a similar noise and re-torquing the shock shaft nut fixed it, but the noise is back after an AutoX and 500 miles.

The noise mostly happens with low load on this corner (I.e. on the back side of higher-speed bumps).

The most unfortunate thing is I am having a hard time tracking down replacement parts.

Thoughts?

Thanks!

 

[2002A]

Interesting. Is that the original (stock) nut(s) on the top of the strut shaft? The locknut on my 2021 M3 had an integrated washer and there were 3\8's to 1\2 inch of threads visible when it was torqued down. I believe the nut that belongs here is very similar to the nut that fits on the upper control arm where it meets with the top of the knuckle. (Part 1111145-00-A) It looks like you might have some play in there so I would do a teardown removing the whole strut assembly by removing the upper control arm mount (4 nuts on top) and closely examine where the top hat of the strut meets the isolater for any gaps or flexibility. Dissasemble everything, check top hat to ensure it is not compromised and then reassemble with a new properly placed isolater 1044031-00-B and use one locknut on the end of the strut shaft with a integrated washer. The other referenced nut could be used with blue loctitie if the proper locknut cannot be sourced. Torque the 3 nuts connecting the top hat to the upper control arm mount while you have still out of the car and then reinstall. Good luck.

 

[Lindenwood]

Interesting. Is that the original (stock) nut(s) on the top of the strut shaft? The locknut on my 2021 M3 had an integrated washer and there were 3\8's to 1\2 inch of threads visible when it was torqued down. I believe the nut that belongs here is very similar to the nut that fits on the upper control arm where it meets with the top of the knuckle. (Part 1111145-00-A) It looks like you might have some play in there so I would do a teardown removing the whole strut assembly by removing the upper control arm mount (4 nuts on top) and closely examine where the top hat of the strut meets the isolater for any gaps or flexibility. Dissasemble everything, check top hat to ensure it is not compromised and then reassemble with a new properly placed isolater 1044031-00-B and use one locknut on the end of the strut shaft with a integrated washer. The other referenced nut could be used with blue loctitie if the proper locknut cannot be sourced. Torque the 3 nuts connecting the top hat to the upper control arm mount while you have still out of the car and then reinstall. Good luck.

Thanks! This is with MPP Coilovers that have been on for about 20k miles. The thin nut securing the shaft to the 3-stud upper mount started stripping so I installed a new full-sized nut with a couple washers to space it back up to the still-good threads (I have since replaced both sides with lock-nuts).

The 3 nuts holding the top hat to the upper control arm mount are definitely torqued and the hat itself is not moving. It just seems the hat’s inner bushings / isolating functions might be damaged?

 

[dsgerbc]

I'm not aware of being able to procure replacement tophats separately. I ended up buying used M3 front struts off ebay just to use the tophats. The one bit of useful info I have - I think you can buy any trim of M3 (or maybe MY too) and the tophats will fit.

The only standalone aftermarket option I'm aware of are Redwood's 'floating' tophats. They *may* work on MPP springs, but you'd be on your own figuring out whatever spacers and spring seats you'd need to make those work. RW currently uses 3" ID springs.

I have those tophats too, and they are probably making a similar noise. Or at least that's where I think it's coming from. Since I get some low-speed rattling up front and everything that could possibly rattle is tight and front sway endlinks are like 3k miles old.

 

[superflyrolla]

Following. I'm curious what it looks like if/when you get it apart.

I wish Tesla sold the top hat as a standalone part. RockAuto has a full front shock assembly for $75. I've thought about buying those just to steal the top hats for quicker swaps.

I also had trouble removing those skinny jam nuts when corroded. I may try a nylon lock nut.

 

[dsgerbc]

I wish Tesla sold the top hat as a standalone part. RockAuto has a full front shock assembly for $75.

Good tip. And the RWD ones are $10 cheaper still.

 

[dsgerbc]

How much preload are you running? Maybe the spring becomes unloaded on rebound and rattles?

 

[Lindenwood]

How much preload are you running? Maybe the spring becomes unloaded on rebound and rattles?

I only adjusted it for ride height. Indeed, with the wheel off the ground I can yank on the springs and get them to tweak one way or the other (within normal tolerances), but they are definitely not loose enough to be floating.

Good thought, though!

 

[Lindenwood]

I disconnected the anti-sway bars and replaced the compression rod with a used factory replacement I bought. No change.

Handling is still crisp and precise, the noises aren’t associated with any specific inputs (i.e. steering or braking), and the noises don’t accompany vibrations through the steering wheel. These tell me the lower hub ball joint, the upper ball joint, and the tie rods should all be fine.

The only thing remaining is the top hat. It could be quite “loose” without otherwise affecting handling or feel in any significant way. That I can lift on the wheel and get 1/4 of audible vertical movement, and also move the shock shaft left/right probably 1/4” using just a screwdriver, feels like a lot of movement for any suspension component under just hand pressure.

I am toying with a few ideas to fill the top hats with perhaps some kind of bonded epoxy putty…

 

[Lindenwood]

Following. I'm curious what it looks like if/when you get it apart.

I wish Tesla sold the top hat as a standalone part. RockAuto has a full front shock assembly for $75. I've thought about buying those just to steal the top hats for quicker swaps.

I also had trouble removing those skinny jam nuts when corroded. I may try a nylon lock nut.

Thanks for the tip! Bought two complete shock assemblies plus two LCAs and another Compression Rod. Going to throw all these on to see if it goes away.

One note, I can physically get the CR bearings to make noise by grabbing the control arm and forcefully wiggling it side-to-side, but swapping in a stock one doesn’t get rid of the noise. (The stock bushing does muffle it some, but the rattle is definitely still there).

 

[Lindenwood]

Whew. I did the upper shock mounts first. No change. Compression rods, no change.

It was the outer ball joints on the lower control arm, maybe the lower shock mount bushing, (or, possibly, the LCABs). Interestingly, all of them very much feel within spec by hand (still very stiff) and prying on them with a small pry-bar. I am too lazy to buy and mount a dial indicator.

My hypothesis: bad roads and autocrossing every month, coupled with the significant reduction in compliance from fully-rigid LCA bearings and CR bearings, put all the remaining strain on the lower ball joint. Moving forward, I’ll consider this a 20k-mile wear item.

Also, annoyingly I just sold my shop press during a recent move so now I need to figure that out again .

 

[Dave EV]

Whew. I did the upper shock mounts first. No change. Compression rods, no change.

It was the outer ball joints on the lower control arm, maybe the lower shock mount bushing, (or, possibly, the LCABs). Interestingly, all of them very much feel within spec by hand (still very stiff) and prying on them with a small pry-bar. I am too lazy to buy and mount a dial indicator.

My hypothesis: bad roads and autocrossing every month, coupled with the significant reduction in compliance from fully-rigid LCA bearings and CR bearings, put all the remaining strain on the lower ball joint. Moving forward, I’ll consider this a 20k-mile wear item.

Also, annoyingly I just sold my shop press during a recent move so now I need to figure that out again .

Useful info - curious, does the new top-hat still allow the strut shaft to move as much as the one in your video? That sure does seems like an excessive amount of movement with low force.

 

[Lindenwood]

Useful info - curious, does the new top-hat still allow the strut shaft to move as much as the one in your video? That sure does seems like an excessive amount of movement with low force.

I have not checked yet, but I’ll try to remember next time things are apart!

 

[dsgerbc]

I have those tophats too, and they are probably making a similar noise.

BTW, I badmouthed those mounts unfairly.
I tracked my noise to a deteriorating ball-joint in the compliance link. I have stiffer whiteline caster bushings. So, I think @Lindenwood 's theory that these ball joints are likely to take a beating has merit. I believe @superflyrolla would agree with that as well.