Major RS2 brake issue...

[A80Avant]

On with my ongoing issues with my brakes, and after already having spent about 2000euros in parts, i was wondering if anyone could add to the issue, or have had something like this related as well.

Story goes:
2004---> first bought the car, and without having any experience with steering fluid, i mistakenly used the red stuff. immediately my steering went bad, and i drained as much as i could out, but eventually after a year or so, had to replace the steering pump. After that, everything was fine until...

03/2010, after a brake disc/pads change, bomb accumulator and brake fluid, i leave from Greece to head back to the UK. I was a bit suspicious about the type of brake fluid inserted until i realised that indeed it was a fluke. After 2-3 months i replaced the brake fluid due to a spongy feeling of the brake pedal, used proper 5.1 from opie oils and also thanks to Paul from autocrafts Berlin, replaced the brake bomb as we thought at the time that this may have also had an issue.

7-8/2010: Indeed bomb was sent back to Paul, and was examined to be able to hold a below standard pressure. New bomb improved things to a good extent. Then the hose going from the bomb to the servo was leaking and i ordered the new one, which Audi replaced with a BRAIDED one rather than the rubber one, although i did order one from the Audi Tradition shop. Ended up having 2 replacement hoses(they were cheap anyway) but used the braided one. Leak was fixed, and brake was still feeling spongy...

sometime end 2010/beg 2011: after discussion with GT500, i buy a new servo from germany, from a shop that tells me that they had it from Audi dealers. A new servo and master cylinder arrives and looks brand new. Rob fits it, brakes are rebled for the milionth time, and brakes feel absolutely perfect! Like butter and good responce!
Thinking that this is the end of it, we leave it at that.....

....But, i could still only lose all pressure on an off engine after 5-10 pedal presses! What the hell? All hoses are fine, no leaks, bomb new, servo new, and it's still doing it??

Another call to Paul for yet another brake bomb, to which i must say that Paul has been a great guy supporting me through this sending me replacement bombs under warranty! So i have this one, which has been the 3d bomb to try out.
At the same time, i decided to give my calipers a refurb as well as change the 2 rear hoses so that we dont have any problems with the pads or calipers relating to these problems. Fit everything up, new bomb, and here is the problem now:

On OFF engine, i still loose pressure after about 5-10 presses.
On ON engine, idling: if i press the pedal 4-5 times all the way, i loose pressure and the pedal goes down juddering!!!!
If i leave it, the pressure builds up again and i have brakes that work.!

SO to make sure that this is not a steering pump problem, i have the pump replaced as well on my local garage as well as the sensor on the servo which seemed to be leaking a bit. So now the problem persists, and when i reach the juddering issue, i get the brake warning light as previously my sensor was faulty!

So to summarise:

Bomb: NEW
Servo: NEW
Sterring pump: NEW
Master Cylinder: This has been kept the same because according to Rob, it is absolutely fine and does not show any signs of wear.

Hose from steering pump to bomb---> was replaced with a new item from VAGPARTS(was leaking early on)
Hose from servo to bomb: new braided hose from audi


Here are the speculations:

1) could the braided hose be partially blocked and therefore not allowing the steering fluid to flow from the bomb to the servo adequatelly? ----> will change the hose to the rubber one i have got from audi to check.

2) Could the servo itself, although new be faulty??? ----> the german shop asked to send it back so they could get a replacement one from audi (hopefully)

3) Could this be a bad batch of bombs/wrong bomb? ----> i find it hard to believe as the bombs i bought from Paul were identical to the original one that was on the car, the car is dated 1995, and i believe the bomb i have is the one building up higher pressure than the rounded one.


Solutions:

? fit an S2/audi 80 V6 servo, (shorter) bought used with a different bomb to servo configuration to see if the problem goes away, and then send the servo back to germany to have it replaced with a similar unit


? Delete the hydraulic servo and bomb all together and use a drum servo. For this we would need a vaccum from the inlet manifold and a good one way valve to make it work. Anyone done this before? Also we would need to blank the parts of the system that work with the hydraulic system.

? Fit another master cylinder 'just in case' to rule out any misnehaving of the current one due to the bad brake fluid?---> but the problem here seems to be with the hydraulic pumping to build the pressure in the system, not the bit that involves the brake fluid bit..



As you can see, this is an issue that has been not only costly but frustrating, as besides are best efforts to make it work, it is on going.... I would appreciate any comments/help available!

thanks
Vas

[A80Avant]

The shorter brake servo comes with a number of : 894612099A which has been used also in S2/V6/2.0 16v and i can get this one:

http://cgi.ebay.co.uk/AUDI-80-COUPE-...item35b14079c7

i suppose the master cylinder will need to be changed to mine to work.

[Phil Payne]

Can you slip the belt off the pump and spin it by hand by pressing on the outer surface of the pulley?

I'm interested in whether it resists once or twice per revolution.

[A80Avant]

hmm, im not following...

[Phil Payne]

Another issue is the new bomb. The supply line from the pump and the exit line to the servo fit on different faces of a cube-like structure under the reservoir itself. Is there a large cross-head cap (like the piston caps on the pump) on another of the faces?

[A80Avant]

not that i recall. the bomb has 2 faces one goes in from the steering pump, the other goes to the servo. no other openings in the cube structure. there is also a top return line if i remember correctly

[Phil Payne]

hmm, im not following...

I've stripped quite a few of these pumps to replace the Rubber Seal from Hell. Two cars with similar problems turned out to have only one high-pressure piston fitted, not two. When I first found one of these, I thought it was a bodge repair - but it seems that some of the later tandem pumps left the factory like this.

The system has (IMO) an inherent design weakness - there is no overpressure relief provision in the pump itself, that's done by the bomb. Problems result if there is a blockage between the pump and bomb - there are two banjo bolts both of which usually have gauze screens and a hose with a constrictor. I wonder if Audi crippled the pump by removing one piston to solve the problem of overpressure popping the O-rings under the caps - that's where most leaks occur.

Anyway - the original tandem pumps fitted to the MB and RR have two pistons driven by an eccentric on the main shaft. The piston seals sometimes fail meaning the pump only pumps once per revolution, not twice. These two 'modified' pumps only ever had one piston, so they only pump once anyway.

I'd like to know which sort you have.

[Phil Payne]

not that i recall. the bomb has 2 faces one goes in from the steering pump, the other goes to the servo. no other openings in the cube structure. there is also a top return line if i remember correctly

OK. I've seen a few with caps turn up recently - I'm wondering if they're rebuilds.

[Phil Payne]

Take the return hose from the servo to the reservoir off at the reservoir end and run the engine. You should see as few as zero drips. Any flow means a defective servo.

[A80Avant]

its getting a bit techincal now, but ill try to see if i understand!

the steering pump i used is the one with a part number used for audi RS2. Since i have it in my hands i can see the part number being: 8G0145165. This pump was working adequatelly the last 6 years, and apparently still is, although it was just replaced yesterday with a new unit (similar) as we thought it was faulty. So the new steering pump is excactly the same with the one the car had(and was working!)

the bomb's banjo bolt mesh was cleaned on the last bomb repair as well. I presume that the other side on the steering pump side was also checked while the pump was being replaced. Otherwise they would have noted that there was a problem with the high pressure hose going to the bomb.

[A80Avant]

I actually tried to take that hose off, but at the servo edge with the engine off, but the pedal not previously pressed to get rid of any steering fluid that was still in the system, and the outcome was this:

on the servo top, there was steering fluid filled to the top, and as i took the hose off, there was a bit of steering fluid which came off, as the hose was removed, and then it stopped.

if i am to do this test, should i first press the pedal with the engine off and then try it? or should it be done with the engine on, and without pressing the pedal at all?

[Phil Payne]

if i am to do this test, should i first press the pedal with the engine off and then try it? or should it be done with the engine on, and without pressing the pedal at all?

No, don't press the pedal. That uses the servo and the fluid used will be expelled along that line back to the reservoir.

It sounds to me like most of the bases have been covered. Of course if the master cylinder's travel is longer than normal you'll use more 'under pressure' servo fluid per depression and that could account for the reduced number of presses. I've met a few cars that simply have to be bled and bled again to get good brakes.

[A80Avant]

well, if i remember correctly we must have bled the car about ..... 4-5 times now already!

if i take the return hose off and run the engine, would that be a sufficient test?

last time i did it, there was some fluid coming out initially, but then it stopped. Something like a few mls, but definitelly more than a drip. Im just not sure i did the test right

[A80Avant]

I need to also add that the return hose from the servo meets the 3T junction coming from the steering rack as well.

if i remove that with the engine idling, wont that leak? Should i have it tapped with my finger or something?

[Guslotti]

On with my ongoing issues with my brakes, and after already having spent about 2000euros in parts, i was wondering if anyone could add to the issue, or have had something like this related as well.

Story goes:
2004---> first bought the car, and without having any experience with steering fluid, i mistakenly used the red stuff. immediately my steering went bad, and i drained as much as i could out, but eventually after a year or so, had to replace the steering pump. After that, everything was fine until...

03/2010, after a brake disc/pads change, bomb accumulator and brake fluid, i leave from Greece to head back to the UK. I was a bit suspicious about the type of brake fluid inserted until i realised that indeed it was a fluke. After 2-3 months i replaced the brake fluid due to a spongy feeling of the brake pedal, used proper 5.1 from opie oils and also thanks to Paul from autocrafts Berlin, replaced the brake bomb as we thought at the time that this may have also had an issue.

7-8/2010: Indeed bomb was sent back to Paul, and was examined to be able to hold a below standard pressure. New bomb improved things to a good extent. Then the hose going from the bomb to the servo was leaking and i ordered the new one, which Audi replaced with a BRAIDED one rather than the rubber one, although i did order one from the Audi Tradition shop. Ended up having 2 replacement hoses(they were cheap anyway) but used the braided one. Leak was fixed, and brake was still feeling spongy...

sometime end 2010/beg 2011: after discussion with GT500, i buy a new servo from germany, from a shop that tells me that they had it from Audi dealers. A new servo and master cylinder arrives and looks brand new. Rob fits it, brakes are rebled for the milionth time, and brakes feel absolutely perfect! Like butter and good responce!
Thinking that this is the end of it, we leave it at that.....

....But, i could still only lose all pressure on an off engine after 5-10 pedal presses! What the hell? All hoses are fine, no leaks, bomb new, servo new, and it's still doing it??

Another call to Paul for yet another brake bomb, to which i must say that Paul has been a great guy supporting me through this sending me replacement bombs under warranty! So i have this one, which has been the 3d bomb to try out.
At the same time, i decided to give my calipers a refurb as well as change the 2 rear hoses so that we dont have any problems with the pads or calipers relating to these problems. Fit everything up, new bomb, and here is the problem now:

On OFF engine, i still loose pressure after about 5-10 presses.
On ON engine, idling: if i press the pedal 4-5 times all the way, i loose pressure and the pedal goes down juddering!!!!
If i leave it, the pressure builds up again and i have brakes that work.!

SO to make sure that this is not a steering pump problem, i have the pump replaced as well on my local garage as well as the sensor on the servo which seemed to be leaking a bit. So now the problem persists, and when i reach the juddering issue, i get the brake warning light as previously my sensor was faulty!

So to summarise:

Bomb: NEW
Servo: NEW
Sterring pump: NEW
Master Cylinder: This has been kept the same because according to Rob, it is absolutely fine and does not show any signs of wear.

Hose from steering pump to bomb---> was replaced with a new item from VAGPARTS(was leaking early on)
Hose from servo to bomb: new braided hose from audi


Here are the speculations:

1) could the braided hose be partially blocked and therefore not allowing the steering fluid to flow from the bomb to the servo adequatelly? ----> will change the hose to the rubber one i have got from audi to check.

2) Could the servo itself, although new be faulty??? ----> the german shop asked to send it back so they could get a replacement one from audi (hopefully)

3) Could this be a bad batch of bombs/wrong bomb? ----> i find it hard to believe as the bombs i bought from Paul were identical to the original one that was on the car, the car is dated 1995, and i believe the bomb i have is the one building up higher pressure than the rounded one.


Solutions:

? fit an S2/audi 80 V6 servo, (shorter) bought used with a different bomb to servo configuration to see if the problem goes away, and then send the servo back to germany to have it replaced with a similar unit


? Delete the hydraulic servo and bomb all together and use a drum servo. For this we would need a vaccum from the inlet manifold and a good one way valve to make it work. Anyone done this before? Also we would need to blank the parts of the system that work with the hydraulic system.

? Fit another master cylinder 'just in case' to rule out any misnehaving of the current one due to the bad brake fluid?---> but the problem here seems to be with the hydraulic pumping to build the pressure in the system, not the bit that involves the brake fluid bit..



As you can see, this is an issue that has been not only costly but frustrating, as besides are best efforts to make it work, it is on going.... I would appreciate any comments/help available!

thanks
Vas

I'm with the same problem. The system is with 47 bar but after press the brake pedal 5 or 6 times the servo pressure drops a lot. If I press a lot of times it comes to ZERO bar. I notice a lot of oil came from the return pipe.

Any idea?

Did you get a solution?