Popping / knocking in front end

[aussieallroad01]

Hi all, the allroad has had a bit of work done a while ago (3000mi), with upper and lower control arms having been replaced, the left hand outer cv as well as the airbags quite some time ago before that.

I haven’t yet done tie rod end or sway bar links, but I believe there was a little slop in the tie rod ends.

In the last couple of weeks it has developed an unusual popping or knocking noise on the left side (of a right hand drive car) which is loud enough to hear in the cabin with the radio off if you’re paying attention. You can also if very careful, just feel a little bit of vibration in the floor.

It doesn’t happen 100% consistently. It doesn’t appear to be related to how hard bumps the car goes over. It doesn’t get any louder with big bumps vs very small. If you’re on the highway going straight it won’t knock at all.

It seems to pop a bit more often when the suspension droops, but will sometimes do it in compression like when turning right into a driveway, but generally seems to do it more when going left or straight over moderate undulations. Again not 100% consistent even when driving over the same road.

I have tried bouncing on the front end while static without being able to create the noise. I have also tried turning the steering wheel when static, and am not sure but there may be a very subtle noise on directional change.

Does anyone have a view of most likely culprits? I haven’t yet had the time to setup a GoPro or something in the wheel housing to try and diagnose further.

[blairdude]

I have a what sounds like a similar noise on mine; more likely to get the sound while going over a bump with the wheels turned, rarely hear it if at all on the highway. On my car I suspect that the inner CV joints may be worn, but further inspection is required.

[mk2_madness]

Popping/knocking noises almost always come from a ball joint style suspension component (tie rod end, control arm end, sway bar link, etc). I suggest that you check to make sure all the control arm bolts are properly tightened. If all those are tight, I would disconnect the sway bar end links and go for a short drive to rule them out. I had a similar noise in my a4 when I first bought it that turned out to be the tie rod ends. How much play / noise do you hear if you rock the wheel from side to side in the air?


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[blairdude]

Popping/knocking noises almost always come from a ball joint style suspension component (tie rod end, control arm end, sway bar link, etc). I suggest that you check to make sure all the control arm bolts are properly tightened. If all those are tight, I would disconnect the sway bar end links and go for a short drive to rule them out. I had a similar noise in my a4 when I first bought it that turned out to be the tie rod ends. How much play / noise do you hear if you rock the wheel from side to side in the air?


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In my case, the control arms, tie rods (inner and outer), sway bar links and bushings are all new, and I've double checked the torque on all of them. Suspension is all tight and does not feel loose while driving either.

[Bordom]

My popping in the front end was due to the rubber strut mounts. Kind of a classic for Audi. CV joints don't typically cause noise unless it's clicking

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[blairdude]

My popping in the front end was due to the rubber strut mounts. Kind of a classic for Audi. CV joints don't typically cause noise unless it's clicking

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Well in my case, when I grab the axle on the left side, I can hear a slight knock from the play in the inner CV. The right side has less play, and makes less noise on the road as well.

I would expect if the rubber upper shock mounts were done, the knocking sound would be present whether or not the wheels are turned. However, turning the wheels will move the inner CV to a different position, which is why it makes sense to me that they could produce my specific symptoms.

[aussieallroad01]

I've reduced the knocking in mine, but there is still one more left, plus I have recently developed a squeak in the same side prior to changing the sway bar linkages.

The worst part of the knocking was a combination of inner outer tie rod ends for the steering plus the bushings been gone on the sway bar linkage. It was interesting in that I could make most of the noise associated with the sway bar linkages go away when i dropped it into the lowest suspension setting. It was far noisier on the higher settings.

Now that those are done, the worst of the knock is gone (esp over smooth droop scenarios) but there is still one that happens on some of the rougher bumps.

What does the rubber on the shock tower insulate? I thought the spring was mounted fairly firmly to the shock tower.

[aussieallroad01]

Ok so interestingly the knock got worse.

What it turned out to be is the shock tower rubbers had completely gone on one side so the top of the shock and centre of the rubber were slapping around inside. Explains why I got some really bad handling behavior once or twice in the rain. The other side was almost completely gone too and was just about to start slapping around as well.

I've swapped in two new full strut and airbag setups, and now I have a completely different knock in *both* sides that occurs under different conditions, but its still worse on the left.

I'm starting to be at a bit of a loss, unless the bad strut destoryed the LCAs or something, I am not sure what else could be going bump.

[aussieallroad01]

Today i have also done the following
- checked out the steering rack bolts under the battery and they were tight
- removed the sway bar and end links, no improvement, if anything the noises got worse

Nothing like a 5 month long hunt for knocks to drive you nuts.

[oasis]

Could it be something unrelated to the suspension? If you have oversized downpipes exhaust could they be moving too much or are aligned incorrectly, hitting the body?

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[ShelbyM3]

Have you checked your subframe bushings? If you’ve got rotted top-hats, it wouldn’t be too much of a stretch to imagine all of the rubber being rotted. Lower control arms bushes like to crumble, too. Does your prop-shaft have any play in it?


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[aussieallroad01]

I'm not sure exactly where all the subframe bushes are but the ones I have found look in ok condition, no cracking, and the flappy hat things are still in good shape

Driveshaft seems ok, the CV's were done recently. Downpipes etc are all factory.

I put a camera under the car to see what could be seen. No obvious things hitting, but a fair bit of movement in the LCA, just hard to say if its normal or not. A lot of it seems forced by the spindle design.

https://www.youtube.com/watch?v=g3zMDSQ-93k
https://www.youtube.com/watch?v=-2ZT2I8qa_Q
https://www.youtube.com/watch?v=NZ1FOef4kIY

[aussieallroad01]

Ok so update on this.

The new struts were preassembled and were missing the strut mount spacers. This meant the top of the strut rod was protruding a few mm more than it should be, and knocking against the strut cover/upper control arm mount, leaving witness marks.

Putting the spacers from the old struts onto the new one gave it a bit more clearance and has solved the knocking finally!

[blairdude]

Ok so update on this.

The new struts were preassembled and were missing the strut mount spacers. This meant the top of the strut rod was protruding a few mm more than it should be, and knocking against the strut cover/upper control arm mount, leaving witness marks.

Putting the spacers from the old struts onto the new one gave it a bit more clearance and has solved the knocking finally!

This is interesting... do you have photos of the spacers? How thick are they? Makes me wonder if mine are missing them too.

[aussieallroad01]

https://imgur.com/a/audi-allroad-struts-CKQAogM