Brake vibrations, bomb and PAS pump replaced

[dave4]

Hi all,

Have a 94 s2 which has problems with the braking system -

The problem(s) are -

Red exclamation warning light flashes
Poor servo assistance (had to press very hard - sometimes twice to stop!)
Constant vibration through the pedal
"Grinding noise" when pedal pressed hard

Took car to an Audi dealer who said it was the "bomb", probably damaged by the previous owner who had put the wrong fluid in . . . . . they quoted me an arm and a leg So got local garage to fit this and PAS pump (supplied by Quattro corner) with fluids flushed and replaced with correct one.

This solved the problem in so much as the brakes now "work" however the vibration through the pedal continues as does the grinding noise.

Have been back to the Audi garage who have diagnosed the same faults as before claiming the bomb must be faulty and when asked said it wasn't a wheel speed sensor.

Does anyone else have any idea what else could be causing this problem, could other components have been damaged by having the wrong fluid in? I guess really what I am after is suggestions for the garage for other things to check . . . . . .

Oh and it fails the bomb "pump" test miserably )-:

Not the most mechanically minded so any help gratefully received

[LHD_Kid]

did you replace with a brand new bomb or a used unit? Only really worth putting a new one in.... if you DID fit new, it really sounds like its the servo seals which are gone....
HTH
Chris

[dave4]

Yup, it was a new one - would replacing the seals solve both the vibration and the grinding noise when braking hard?

[Knight Rider S4]

By what you say the it sounds like a ABS fault..HAve you had the car scanned with vag.com? and if so do you have a fault code list..Another thing have you tried to take out the fuse for the ABS to see if that made a difference

[dave4]

I asked the Audi garage to check the sensors after looking on the forum, they said there weren't any fault codes . . . . don't know if they did however.

What fuse is it for the ABS - I'll whip it out now (oo-err missus) and see if that solves it,

If it is the servo seals is there anything obvious I could check? (It doesn't seem to be losing fluid)

Cheers for the suggestions!

[LHD_Kid]

As Mr Rider says, also sounds like could be ABS fault....
If the servo seals are gone, you wont lose fluid, you just dont get the build up of pressure, which is why you will fail the bomb test...
you can remove the fluid line from the servo, and see if fluid leaks..... have a search on testing the servo, it will be clearer on which line to remove... its either on the forum or s2central, can't remember
its the return one I think, which you need to take out... if it drips more than once or twice, its deffo the servo...
Easier to try the ABS fuse and faullt codes first and move on from there.....
you have eliminated the bomb, which is a pretty common cause of this type of fault....!

[LHD_Kid]

Having a few minutes spare.... I had a quick scout round...
The SJM site throws up some useful info as usual.... here you will find some diagnostic tips and also how to replace etc.... stuff about ABS, and also a diagram of the servo, etc...

CLICK HERE

Chris

[Knight Rider S4]

Beat me to it Chris...Happy Birthday you old git

[dave4]

Cheers for all your advice -

Pulled the ABS fuse (fuse 31?) and no change - pedal still vibrates . . . . .

I'll do the servo check on S2central tomorrow - if the servo seals have gone what would this entail repair wise ie how much is it likely to cost me )-:

Cheers!

[dave4]

Oh and Happy Birthday mate!

[Cullam3n]

I'm going to guarantee it's the servo on this one, sounds like the same symptoms I had

[LHD_Kid]

Cheers boys...

Do the leak test on the servo, decription also on the SJM link...
The servo is not user repairable... I have tried to get a couple repaired but doing this by post is proving difficult, although I know there are places which can do it - for a price...
Best bet, if it turns out to be the servo (which I really suspect it is) is to find a good used one...
Good luck
Chris

[Cullam3n]

How did I miss that, happy birthday Chris Slightly OT but have you made any progress on the bad servos you got ahold of?

edit: probably would be better if I read your post

[dave4]

evening all,

Pulled the ABS fuse (31) and took her for a spin, the "grating" noise has gone . . . .
I forgot to say on previous post that this only happens when coming to a stop, any ideas as to what part of the ABS system this would be related to? Wheel speed sensor maybe?

As to the servo test, could anyone post a photo with a big red circle round the pipe I need to disconnect? I "think" I know what I'm looking for, but I aint that mechanically minded (confident ;-) !!

[dave4]

Hi all,

I have located the servo return pipe - its a ****** to get a spanner to!

Can I do the servo test by disconnecting from the "Y" junction about 10cm further down the pipe instead of from the top of the servo? - Its got a jubilee clip which looks a bit more accessible.

I've circled where I mean in the attached photo - could someone have a look
and let me know?

cheers