ABS, brake fire, a mess

[mj2.7]

Long story less long. My abs light and blinking red brake light were coming and going, my brakes needed to be done anyway so I had my brakes done. New front rotors and pads. The abs and blinking brake light continued to come and go. Then they happened at start up everytime. So I talk to the shop, they say bring it in but you should be fine, just no ABS. So I let it go a little too long. Front passenger brake locks up on the highway and heats up. The rotor needs to be cut, the shop(who are not audi experts) think the fluid may contaminated and may have expanded to cause the lockup and heat up. So they want to change the fluid and bleed the whole system. They cant figure out how to turn on the abs pump on to bleed. I am going to bring my vag-com over and see if I can turn the abs pump on. Is their another way? Is this/can this be related to the abs and blinking brake light. What do I need/should do about the whole situation? Bleed the system and see what happens? or do I need to replace the abs unit, and what is involved in that? I am low on money which is why I didnt take care of the abs light right away. The shop is a friend and he will work with me, just not an audi expert.

[mj2.7]

Caliper tested fine and the lines look in good condition.

[tester123]

I guess (from your userid) it is a 2.7T? Year etc. details would help. Also, get the codes first. It is difficult to say anything without codes.

Shooting in the dark, it could be the ABS control module sending mixed signals... locate it and check for any water/other damage. It is also possible that other wiring issues may exist. Get the codes and go from there.

[mj2.7]

2000 2.7t 6spd

Ill try to get the codes, trying to piece together an old laptop now, my vag com has an old serial connection.


I was hoping my next vehicle would be a Diesel pickup, just need this A6 to last another 2 years.

[jseklund]

I wouldn't expect fluid to cause a lockup like that. My first guess would be the caliper, which you checked. If that has been thoroughly checked out and is fine, I would park the car with everything connected, raise the wheels and spin them. For instance, if it's your front wheel that locked, I would raise both front wheels off the ground and give them a good spin. It should spin freely for a little while (maybe 1-2 turns).

I would then pump the brakes and see if the caliper appears to clamp down on the wheel that is seizing. If you can see it wiggle, you know the fluid is pushing the caliper closed - so it is getting fluid.

After a few pumps, I would spin the wheel again. You may find that you can spin it by hand but as soon as you let go of it - it stops much more quickly than you pumped the brakes. This, of course, means the caliper is NOT backing off (which is what we suspect), but it is getting fluid - so the master cylinder is at least pushing out the fluid correctly.

If this happens, then I would look at the brake lines next. Brake lines can become obstructed in such a way that they start to act as check valves - fluid flows one way but not back. So you push the petal down and the fluid closes the cylinder, but there contamination won't allow the fluid to flow back and release the cylinder. I've seen it happen twice and I have seen people replace numerous parts chasing it.

[2.7Lturbo]

Originally Posted by jseklund

I wouldn't expect fluid to cause a lockup like that. My first guess would be the caliper, which you checked. If that has been thoroughly checked out and is fine, I would park the car with everything connected, raise the wheels and spin them. For instance, if it's your front wheel that locked, I would raise both front wheels off the ground and give them a good spin. It should spin freely for a little while (maybe 1-2 turns).

I would then pump the brakes and see if the caliper appears to clamp down on the wheel that is seizing. If you can see it wiggle, you know the fluid is pushing the caliper closed - so it is getting fluid.

After a few pumps, I would spin the wheel again. You may find that you can spin it by hand but as soon as you let go of it - it stops much more quickly than you pumped the brakes. This, of course, means the caliper is NOT backing off (which is what we suspect), but it is getting fluid - so the master cylinder is at least pushing out the fluid correctly.

If this happens, then I would look at the brake lines next. Brake lines can become obstructed in such a way that they start to act as check valves - fluid flows one way but not back. So you push the petal down and the fluid closes the cylinder, but there contamination won't allow the fluid to flow back and release the cylinder. I've seen it happen twice and I have seen people replace numerous parts chasing it.

off topic of the OP, but what can you do to stop the rotor from rattling around? mine just sits there and because of the floating caliper design rattles over bumps , but goes away when i hit the brakes

[GTA_Driver]

Had this same problem in my A4, it can be repaired, but I had my trustworthy shop do the work, so I don't recall exactly. Something to do with caliper seats/pins.

[4Driver4]

Originally Posted by 2.7Lturbo

off topic of the OP, but what can you do to stop the rotor from rattling around? mine just sits there and because of the floating caliper design rattles over bumps , but goes away when i hit the brakes

If your rotor is rattling around, your lug bolts are loose and should be addressed immediately.

[jseklund]

I agree with 4D4 on the rotors rattling - are you sure it's not a tie rod or control arm that you hear rattling as you go over bumps?

When the lugs tighten down, they pull the wheel, hub and rotor together and they shouldn't be able to physically "rattle".

The caliper, on the other hand, may rattle against the rotor - which most likely means the caliper slide pins were not installed correctly or the caliper bracket is not tightened down correctly...

[SloopJohnB@mac.com]

Flatbed the car to a competent audi shop.