proper bleeding of brake system
02-10-2004, 05:53 PM
#1
New Member
Thread Starter
Join Date: May 2001
Posts: 86
Likes: 0
Received 0 Likes
on
0 Posts
proper bleeding of brake system
I just had new rear calipers, rotors and pads installed after my rear calipers were frozen up. I have a 99 A8 with 90k. I just picked up the car and it doesn't feel like they bled the brake system properly. The pedal feels mushy and goes down further than before. Is there a special process for bleeding the brakes?
Thanks
Thanks
02-11-2004, 06:11 AM
#4
Elder Member
Join Date: Mar 2001
Posts: 11,968
Likes: 0
Received 0 Likes
on
0 Posts
Brake bleeding quirks ...
You're guaranteed to get a lot of air in the system whenever you change a caliper. At best, another heavy bleeding is required.
At worst, the reservoir ran dry as Dave said, or the caliper was disconnected long enough to let air bubbles migrate back up into the ABS pump and/or the master cylinder. Bleeding the master cylinder is a PITA. Bleeding the ABS pump buy-the-book requires a VAG tool to run the pump while bleeding. I "bleed" the ABS pump by driving the car, braking had enough to activate ABS system, and then bleeding the calipers again. This seems to work, but I don't know if I've ever really gotten air into the ABS pump.
Brake bleeding in general:
1. Cars without ESP
I recommend a pressure bleeder like the <A HREF="http://www.motiveproducts.com/">Motive Power Bleeder</a>. Especially on a high mileage car, the normal brake pedal down-up-down-up method risks over-stroking the master cylinder. The master cylinder's seals can get scored if they're pushed into a normally unused, and corroded, region of the master cylinder's bore. If this happens, you'll have a very soft brake pedal and will need a new master cylinder.
With the Motive bleeder, pressurize the master cylinder to 20 psi max, and bleed the calipers in the following sequence.
right rear
left rear
right front
left front
2. Cars with ESP
Same as above, except pressurize the master cylinder to two bar (29 psi). This scares me to death, I have visions of splitting the brake fluid reservoir and making one heck of a mess. Also, the bleeding sequence is different on ESP cars,
left rear
right front
right rear
left front
<img src="http://www.motiveproducts.com/Power%20Bleeder.JPG">
At worst, the reservoir ran dry as Dave said, or the caliper was disconnected long enough to let air bubbles migrate back up into the ABS pump and/or the master cylinder. Bleeding the master cylinder is a PITA. Bleeding the ABS pump buy-the-book requires a VAG tool to run the pump while bleeding. I "bleed" the ABS pump by driving the car, braking had enough to activate ABS system, and then bleeding the calipers again. This seems to work, but I don't know if I've ever really gotten air into the ABS pump.
Brake bleeding in general:
1. Cars without ESP
I recommend a pressure bleeder like the <A HREF="http://www.motiveproducts.com/">Motive Power Bleeder</a>. Especially on a high mileage car, the normal brake pedal down-up-down-up method risks over-stroking the master cylinder. The master cylinder's seals can get scored if they're pushed into a normally unused, and corroded, region of the master cylinder's bore. If this happens, you'll have a very soft brake pedal and will need a new master cylinder.
With the Motive bleeder, pressurize the master cylinder to 20 psi max, and bleed the calipers in the following sequence.
right rear
left rear
right front
left front
2. Cars with ESP
Same as above, except pressurize the master cylinder to two bar (29 psi). This scares me to death, I have visions of splitting the brake fluid reservoir and making one heck of a mess. Also, the bleeding sequence is different on ESP cars,
left rear
right front
right rear
left front
<img src="http://www.motiveproducts.com/Power%20Bleeder.JPG">
Thread
Thread Starter
Forum
Replies
Last Post
Redneck Truck
A6 / S6 (C5 Platform) Discussion
21
01-16-2014 06:34 AM
JazzGuitarist
Audi 90 / 80 / Coupe quattro / Cabriolet
1
10-15-2003 01:28 PM
