DK-man

Hello everybody, maybe you can help me (as my local garage has given up).

My car is a '96 A8 2.8Q, 80,000 Km.

Diagnosis: there is a sound like if something is loose (worn bearing or something) around the front wheels (particularly on the left hand side). It is most noticeable when driving on rough roads or over small bumps when the suspension moves rapidly, and not when passing speed bumps, etc. As soon as I touch the brakes the noise disappears - I don't have to break hard, just slightly touch the brakes.

I have had the car to the shop 3 or 4 times and they have checked all front bearings, arms and bars (even replaced some), checked breaks and pads, etc. Nothing has helped at all. The problem has been there since I bought the car about one year ago. Front break pads where changed some time ago, and did not make any difference on the noise.

My theory is that it the problem somehow has to be connected to the brakes or brake system as the noise is so dependent on touching the brakes. I can't believe it is related to suspension, arms, etc, but maybe I am wrong!

I am really hoping that some of you guys out there have some good ideas!

Xialater

it actually probably is something suspension related.....Does the problem get worse at higher speeds, or does it seem more noticeable when turning?? I had a problem like this with my '97 before I sold it, a light "thumping" sound, which was speed sensitive, got worse when I was accelerating, and turning, disappeared entirely when braking. Ended up replacing a CV boot that was torn, and one of the control arms. AND, to make it worse, the local dealership had the same statements to me, that they couldn't reproduce the sound, and they couldn't find any problems. It actually got found when I was having snows put on, and the guys at the tire place noticed the problem, and found this broken control arm. I'd say try getting a second opinion from a different mechanic, see if a second set of eyes sees anything differently

ryoung

.
In my case, the "problem" is caused by a front brake pad sometimes moving around in the caliper.

With my Alcon's, that tuning fork shaped contraption on the top center of the caliper holds the pads in the caliper, but the retainer just barely touches the pad frames.

<img src="http://pictureposter.audiworld.com/17157/alconta6_a.jpg">

I change pads frequently (every time I go to the track), and sometimes it seems to take a couple of weeks before the pads settle in and find a home where they don't move. Before this happens, I sometimes notice a faint noise that sounds exactly like you describe, and I was initially completely convinced it was a suspension problem.

This has happened three times now (twice on the left side, once on the right) with a front pad change. Taking a wheel off and playing with the pads "by hand", I never could detect any movement, but I finally convinced myself that pad movment was the problem.

I don't know how likely this is to happen with the floating caliper of an A8; but if this is it, it's not serious and will hopefully go away on it's own.

PaulW

It sounds like one of your nylon bushings is bad on one of your lower control arms or it has a bad knuckle joint.

This is where it would mount to the frame, the picture below shows how it is connected to the frame, this is the curved control arm, has a nylon bushing in it (right behind the wire):

<img src="http://pictureposter.audiworld.com/47667/dcp_0810.jpg">

Only the weight of the car and force of going over the bumps causes it to move, otherwise it appears tight when the wheel is jacked up.

When you put the brake on, it provides a rotational force on the joint, seating it in place so it doesn't have the ability to knock anymore. It basically puts in a shoulder to support it with the braking force of the car.

It could be something else, but I had something very similiar happen to my on the rear suspesnion on my 91 200q, it was a worn bushing that would sound like somebody was taking a hammer to the rear floor board going over bumps when the car was lightly loaded.

If people were sitting in the back or I had the brakes on, it preloaded the bushing so it could not clunk. Changed the bushing and presto, sound gone.

I would be looking at the lower front control arms, there is a straight one that is very easy to replace and a curved one that is harder to replace. You can get these control arms from Wendy Hager, email <a href="mailto:snolvr8@hotmail.com">snolvr8@hotmail. com</a>, for about 1/2 of dealer cost and they are the same piece. She is hihgly recommended.

Good luck.

pw

Egil A64.2s - S6

going away during even a light application of the brakes. Try putting some heavy grease on some of the joints to see if it will muffle the noise. If it does you have your culprit. If not then it may be something else, like the brakes. The grease will not solve the problem by may assist in a diagnostic.

mclarenm8d

I've had this stuff replaced three times (2 on one side) on my A8, and twice (one each side) on the A4 my wife and I had.

As far as I know, all late 90's Audis have this problem. I've been told the root cause is a mismatch in wear of materials.

Had this fixed on the A8 for iteration numbero three just last month, I'll dig up the shop info and parts list this evening.

DK-man

Thanks a lot everybody for a lot of useful advice. Just a few clarifications: the noise does not seem to be dependent on either speed, turning or engine load as some of you mention. And I also must emphasize that a really gentle touch on the brakes is enought to stop the sound immedeatly.
Any other comments, before I go back to the shop?

RCBENZ2

Sounds like a CV joint or wheel bearing to me.