Brake pedal vibration/chatter - Page 2

littleyellowbat · 05-11-2012, 06:50 AM

thanks for the info. The fluid looks dark enough that I think I'll flush it per your suggestion. Is it best to remove the accumulator and turn the steering several times to flush the old fluid out?

I unplugged that servo wire while the car was running when the light was on. Light did not go out when I unplugged it.

If it turns out that the pump is the problem is it a lot of labor to disassemble it and put new seals in it or is better to just get a new one?

Thanks again.

UrS4boy · 05-11-2012, 02:35 PM

Quote:

Originally Posted by littleyellowbat

If it turns out that the pump is the problem is it a lot of labor to disassemble it and put new seals in it or is better to just get a new one? Thanks again.

Go to the diagram linked below and then click on the Power Steering and Brake Pump label at the front of the car. Then follow the various links.

http://members.shaw.ca/speedtek/UrS%...sis%20Map.html

Jay Matthew · 06-18-2012, 08:03 AM

change the fluid

sanadrustom · 07-05-2012, 10:26 AM

hi guys I hope someone can help me. I bought a 1995 Audi s6 last night and when I was test driving it i felt the brake pedal pulsing/vibrating in sync with the engine ( or so it seems). I been reading all over this website and a few suspects can cause such a thing but I wanted to get more info if anyone is able or experienced with this. it could be the bomb ( problem is when the car is of brake pad doesn't get stiff) would that indicate that its the bomb? 2nd the car hasn't been driven a lot since 08 or most of its life as I have records from the owner that break callipers where replaced in Aug of 2008 and the car had 21500 kms and now it has 229000 kms. could be the brake master cylinder? I'm out of ideas I checked all fluid levels every thing is where it should. I am mechanically good and I work on my cars on my own so most often than not I know what I am doing but this is got me stomped. I also read that the hydraulic reservoir for the PS is the same for the brake bomb and would I feel a vibration/shake on the steering wheel if something like that was effected. sorry for the long essay I hope someone can understand and give me pointers. oh also in of his service records somethign mentions a leak from the L>F calliper and it doesnt look like its been looked at( this is after the major calliper work in 08) thanks again guys SANAD!

scarman · 07-05-2012, 03:11 PM

No, to all your guesses. If the brakes operate normally and the pedal feel is fine otherwise, then most likely the rotors are warped or have pad/rust deposits maybe because of the long inactive period. This is just generic brake knowledge and nothing specific to the S6 brakes.

"Problem is, when the car is off (engine not running), the pedal doesn't get stiff." Have I deciphered that sentence correctly? It's hard to give advice when the post is unreadable.

On a normal system, the hydraulic boost does make the pedal feel softer that many vehicles. After shutdown, it may take as many as 30 pedal applications before the accumulator pressure is depleted and the brakes have no hydraulic boost. It would not be until then that the pedal would become hard to depress. More importantly, do the brakes stop the vehicle with ease when the engine is off ? When the pedal becomes hard, you have no boost pressure to assist in applying the brakes and the car will be very difficult to stop from any speed.

littleyellowbat · 09-24-2012, 08:10 AM

I thought I would provide a little update since I posed some questions earlier in this thread.

I replaced my brake accumulator this weekend since I had a rebuilt one hanging around. This fixed my intermittant red "Brake" light coming on (which I have had for almost a year now).

I did not expect this to fix my problem since I could do about 40 presses on the brake pedal, after turning off the car, before the pedal got stiff. Normally as the accumulator looses Nitrogen pressure the number of presses will decrease to 20 or less and you then know that it needs replacement...mine was at 40 though. However there also is a check valve in the accumulator which apparently also posses a failure point.

Keep in mind that doing the brake pedal push test will not tell you if the check valve in the accumulator is working correctly.

06-18-2012, 08:03 AM	#13
Jay Matthew AudiWorld Newcomer Garage is empty, add now Join Date: Jun 2012 Posts: 5	change the fluid __________________ Davie Motors www.daviemotors.com

07-05-2012, 10:26 AM	#14
sanadrustom Audiworld Junior Member Garage is empty, add now Join Date: Jul 2012 Posts: 31	1995 audi s6 brake pedal pulsing hi guys I hope someone can help me. I bought a 1995 Audi s6 last night and when I was test driving it i felt the brake pedal pulsing/vibrating in sync with the engine ( or so it seems). I been reading all over this website and a few suspects can cause such a thing but I wanted to get more info if anyone is able or experienced with this. it could be the bomb ( problem is when the car is of brake pad doesn't get stiff) would that indicate that its the bomb? 2nd the car hasn't been driven a lot since 08 or most of its life as I have records from the owner that break callipers where replaced in Aug of 2008 and the car had 21500 kms and now it has 229000 kms. could be the brake master cylinder? I'm out of ideas I checked all fluid levels every thing is where it should. I am mechanically good and I work on my cars on my own so most often than not I know what I am doing but this is got me stomped. I also read that the hydraulic reservoir for the PS is the same for the brake bomb and would I feel a vibration/shake on the steering wheel if something like that was effected. sorry for the long essay I hope someone can understand and give me pointers. oh also in of his service records somethign mentions a leak from the L>F calliper and it doesnt look like its been looked at( this is after the major calliper work in 08) thanks again guys SANAD!

07-05-2012, 03:11 PM	#15
scarman AudiWorld Senior Member Garage is empty, add now Join Date: Sep 2009 Location: Knoxville, TN Posts: 611	No, to all your guesses. If the brakes operate normally and the pedal feel is fine otherwise, then most likely the rotors are warped or have pad/rust deposits maybe because of the long inactive period. This is just generic brake knowledge and nothing specific to the S6 brakes. "Problem is, when the car is off (engine not running), the pedal doesn't get stiff." Have I deciphered that sentence correctly? It's hard to give advice when the post is unreadable. On a normal system, the hydraulic boost does make the pedal feel softer that many vehicles. After shutdown, it may take as many as 30 pedal applications before the accumulator pressure is depleted and the brakes have no hydraulic boost. It would not be until then that the pedal would become hard to depress. More importantly, do the brakes stop the vehicle with ease when the engine is off ? When the pedal becomes hard, you have no boost pressure to assist in applying the brakes and the car will be very difficult to stop from any speed. __________________ Tom '95 S6 '95.5 S6 avant

09-24-2012, 08:10 AM	#16
littleyellowbat Audiworld Junior Member Garage is empty, add now Join Date: Jul 2010 Posts: 22	Update I thought I would provide a little update since I posed some questions earlier in this thread. I replaced my brake accumulator this weekend since I had a rebuilt one hanging around. This fixed my intermittant red "Brake" light coming on (which I have had for almost a year now). I did not expect this to fix my problem since I could do about 40 presses on the brake pedal, after turning off the car, before the pedal got stiff. Normally as the accumulator looses Nitrogen pressure the number of presses will decrease to 20 or less and you then know that it needs replacement...mine was at 40 though. However there also is a check valve in the accumulator which apparently also posses a failure point. Keep in mind that doing the brake pedal push test will not tell you if the check valve in the accumulator is working correctly.

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