Hello Everyone,

I am having issues with a brake job on a 2001 Audi A4.

We replaced the front and rear pads. The rotors were a little worn however; we opted not to replace the rotors at this time. The rotors currently have a small (1-2mm) lip on the outside edge.

After reassembly of all 4 calipers and pads, we bleed the system using two people, 1 pumping the pedal while the other cracks the bleeder valve on each caliper starting on the passenger side rear, DS rear, DS front, PS front.

We used a small clear tube running into a fluid reservoir to prevent air going into the caliper while bleeding.

We also used a piece of wood on the floor to prevent damage to the master cylinder.

We were able to get good constant pedal pressure on 4 different instances with the wheels off, however, when we put the front wheels back on, the pedal would lose pressure and require a pump or two to regain pedal pressure, indicating the system still had air in it.

We bleed the system for hours with the front wheels ON, however, after waiting ~30 seconds the pedal would loose pressure and feel spongy like the system still had air in it.

During this process, we removed the wheels and re-bleed the system successfully but every time we replaced the front wheels, the pedal would go to the floor after a few moments.

Given the fact the rotors had an irregular surface, bleeding with the wheels off slightly mis-aligned the rotor due to the fact the pads arenâ€^TMt set yet. Considering we were able to bleed the system without issue with the wheels off, this leads me to believe the master cylinder is good.

Question:

1. Is there another bleeder valve on the ABS actuator that requires bleeding?

2. When re-aligning the rotor to replace the front wheels, this action may force the front caliper piston in slightly. Would this cause air in the lines or possibly push air into the ABS actuator? Considering we bleed the system for hours without any sign of air in the line with the wheels ON, I donâ€^TMt think air remains in the system unless we are missing a bleeding point (abs actuator)?

3. Is it possible the 1-2mm ring around the outside and inside of the rotor could cause this issue given the fact the pads arenâ€^TMt fully seated with the surface of the rotor? Our next plan of action to determine if this is the root cause of the issue is to replace the new pads with the old ones and attempt to bleed the system with the wheels on. If this test is successful, the finger would point to the rotors…

This is very odd issue to say the least.

Any help or advice is appreciated.


Gary (Dallas)

 

the brake system is vac assisted "brake booster"

 

Order:
Passenger Rear
Driver Rear
Passenger Front
Driver Rear

No air in my lines, but I upgraded to SS lines<ul><li><a href="https://forums.audiworld.com/a4/msgs/2412834.phtml">Link to my post</a></li></ul>

 

did you bleed the clutch master cylinder if 5spd?

 

brakes are your lifeline

 

It's an auto.

 

I have bleed the brakes on other cars, motorcycles,Shifter karts, trucks etc. muliple times without issue.

I have a mity-vac vacumm pump that we used to remove all the air initially. This only pulls about 30psi. In my experience, having a helper pump the brakes while someone cracks the bleeder valve is the best method.

Keep in mind, I have clear constant fluid going into my fluid res/catch can that is attached to a clear tube/Bleeder valve at all times. There is no indication of air in the lines other than the fact the pedal requires 2 pumps to get the pedal off of the floor (bad) and engage the brakes.

What is odd is when the front wheels are off, the brake pedal feels normal(good) after bleeding but this moves the rotor slightly out of alignment.

When the front wheels are re-installed, we have to realign the rotor slightly - inturn, recreating the dead pedal issue.

Please help.

Gary

 

Or did you have a procedure for bleeding the abs actuator?

Please reply,

Gary

 

upon hitting the brakes, the pedal goes to the floor and requires another pump or two before the brakes engage.

We are bleeding the brakes with the car turned on.


Gary

 

I've bled many a brake on Audis, never with the key on, never by pumping the pedal..

it's entirely possible that you damaged your master cylinder, even though you had a block of wood beneath the pedal.