lhmagma

Any thoughts?

My wife's 98 A8 4.2 has been warping rotors (front and back) every 5M miles. This has beening going on since we purchased the car 2 years ago(the car had 19M miles when we purchased it and currently has less than 50M).

Audi has been paying for the fix (new rotors and pads or resurfacing) each and every time. Nonetheless, I've grown tired of the frequent visits and the ridiculessness of the situation. Furthermore, I'd like to be able to sell the car with good consience at some point in the future. Lastly, one would think Audi would want to solve the problem instead of paying the dealer to put bandaids on it.

I recently called Audi prior to taking the car in to bring all of this to their attention. They confirmed that there must be something wrong my car as this is not a common problem with A8s. They also said the they would send a rep. to the dealer to work with them to solve it. The car has been at the dealer since Monday this week and the dealer is telling me they've had no contact from Audi regarding the car. As such, the dealer has done what they normally do - replace the rotors and pads (although they have in the past just resurfaced the rotors).

Any thoughts on how to solve this?

HZach

Same thing happened to my '98 as well. Dealer replaced Rotors and Pads, but 5M miles later, the car started to shimmy again when applying the brakes. This went on until the car was out of warranty. Finally went to my local independent, who replaced the rotors again,but pointed out, that it is important to remove all of the protective coating from the rotors before installation and, like 1T mentioned as well, to set the brakes hard.
Have not had any trouble for last 20m miles.

ryoung

Has the dealer been measuring the runout of these rotors and actually confirmed the both front AND rear rotors are really warping? Or ... is he responding to complaints of brake pedal vibration and just replacing rotors and pads?

Needless to say, you should not be having this problem. I'm a little concerned that the repeated replacement of parts without actually diagnosing the real problem may mean that something as simple as #6 in the x-post may be the problem.<ul><li><a href="https://forums.audiworld.com/a8/msgs/14573.phtml">Causes of brake pedal vibration</a></li></ul>

lhmagma

Thanks. To reply:

1) On all but one occasion has a dealer (note: I switched dealers after the first failed to fix the problem after 2 tries) not confirmed warped rotors. For this exception, the dealer had indicated that a dirt buildup between the wheel and mount was the culprit. This however proved to be inaccurate.

2) The problem has occured with both the front and rear rotors. This makes me think that the chances for #6 being the problem are low. Also, the fronts and backs don't warp concurrently.

3) In some cases (and over my objection), the dealer has not replaced the rotors but resurfaced them. In all of these cases, the symptom has resurfaced much faster.

4) To clarify the symptom: A slight shimmy usually starts while breaking through a "window" (say 42 -28 MPH). The shimmy becomes stronger and the size of the "window" grows wider rather quickly over time. Also, I don't have all of the records with me so I can't confirm but higher window speeds (around 60) have usually indicated a problem with the fronts vs. lower window speeds (around 40) for the rears.


Thanks again.

mclarenm8d

The situation you are facing doesn't make sense to me, something is not right. I almost wonder if the brakes are dragging, however it is a rarity for that to become a problem in normal operation.

My wife uses brakes hard and to 1T's point she would drive an hour and a half each day in the local "areas where the average main thoroughfare's speed is 45 - 50 mph" scenario -&gt; Stop and heat the rotors, start, accelerate to 50, stop and heat the rotors, cycle all over again, over and over. We were able to get 20,000 miles out of a set of pads and rotors in this hellish-nightmare operational environment scenario.

lhmagma

Sorry - first window speed should read 42 to 38 - not 42 - 28.

lhmagma

Thanks. I'll try your reco.

One item related to your experience:

Needless to say, I've had more than a few discussions with Dealers and Audi related to "who pays". In all cases, Audi has payed although there was one case were they initially said no but changed this to a yes after a few discussions. More importantly, and specific to your experience, they have assumed responsibility (for this last round anyway) not under the Audi Assured program but under the parts (rotors) warranty which is good (I'm told) for 12M miles.

lhmagma

Thanks. I'll follow your recos. Hopefully soon as the car has been at the dealer since Monday.

Also, in reply to your question, I'd say 66% is highway and 33% secondaries. Avg. speed on the secondaries is probably 35 mph. This is a bit of a simplification, but in Atlanta your either doing 75 + on the highway, stop and go on the highway or 25 to 45 on the various secondary-type roads.

Thanks again.

lhmagma

Thanks.

I too thought about the "dragging" but wasn't sure. It would mean that all four are dragging given that all rotors have been affected at some point. Furthermore, I'm as certain as I can be that it's not driver-induced as my wife put 50M+ miles on an A4 Avant after which I drove another 5M hard miles before it needed a set of new rotors.

As for driving conditions, the car has not been subjected to a tough life. It's rarely driven during our "hellish" rush hours here in Atlanta. Additionally, it consistently averages between 19 and 20 mpg.

Thanks again.

PaulW

You have front and rear rotors warping. They do it over and over again with only 5K on them. Does the dealer check the new rotor thickness and compare it to the warped rotor thickness?

This is something you would want to do. After 5K miles the thickness should be almost identical. I think they are 25 mm thick new and have a wear thickness of 23 mm. Don't quote me on that.

And what is the total indicated runout mounted on the car? The dealer should dismount the wheel, screw the wheel bolts back in, torque them, and measure runout with a dial indicator. My personal acceptance criteria for runout would be 0.002", anything over that and you'll find that your brakes will feel warped.

If all rotors are having problems, then it could be something not completely releasing hydraulic pressure. This can lead to brake rotor warping when the rotors heat up, even the way your wife drives the car they heat up.

So this would point me in the direction of the master cylinder or possibly the ABS pump. I do not know what the internals of the ABS pump look like, so I really don't know if this could be a problem or not, but it is in the circuit.

First thing I would do is check wear levels after 5K miles, and see what they are. I would also check the new rotor exact thickenss to set a starting point. If the brake pressure is sticking, then they will wear the rotors rapidly.

I would also have the brake fluid flushed, and check for any fault codes on the ABS system.

pw