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S2 Coupe Brake / ABS Bleeding Issue
S2 Coupe Brake / ABS Bleeding Issue
So going slightly mad with this issue.
As it’s the last thing stopping me getting my S2 Coupe restoration MOT’ed and back on the road after more than 20 years of being neglected and stood by the previous owner.
The issue being, it takes 3 pumps of the brake pedal to get a reasonably firm brake pedal!
The first pump go’s practically to the floor.
Second about half way down,.
The third about 20mm travel giving an OK (ish) pedal feel, hold your foot on the brake and it does feel spongey, as if there is air still in the system.
Leave the brakes for 5 minutes and I’m back to 3 pumps to get any kind of brake pedal, the S2 dose stop when driven but doesn’t fill you full of confidence!
This is a long post, I'll cut to the question (the full backstory is below).
Would anyone know how to manually trigger the ABS Unit (NOT using VCDS) to cycle the ABS pump to bleed air out of it on an S2 Coupe?
Any constructive help / advice appreciated
------------------------------------------------------------------
Backstory
Blead the brakes so many times and methods, loosing track.
Blead Calliper’s:
RR --> RL --> FL -->FR
RR --> FR -->RL --> FL
FL --> FR --> RL -->RR
And just about any other permutation of this sequence, with the engine off & running.
Also done old school 2 man pump brake pedal & hold method.
Power Bleed at 20PSI from master cylinder reservoir.
And 20PSI reverse bleed from each calliper back to master cylinder reservoir.
The S2 has had new master cylinder, new vacuum ATE brake booster, refurbished standard S2 callipers front & rear and all new copper brake lines with Goodridge braded hoses.
The only old parts reused were the brake compensator & ABS Unit.
Can’t see any obvious bleed nipples on the brake compensator & ABS Unit.
Have done a load of research on line, this seems to be a common issue with ABS systems in general when any kind of major work has been carried out and generally requires the ABS unit to be cycled/blead with tools like VCDS for example.
So have managed to piece together (from various posts) the below ‘VCDS ABS Bleeding Process’.
Confident I was on to a winner dug out my VCDS HEX V2 with OBD 2 x 2 adapters only to find my 1991 S2 Coupe isn’t listed / supported in VCDS just the 1992 on S2.
Gave it a try anyway, VCDS did pick up some issues, (a good thing I thought as it was talking with the controllers), so tried the ‘Select Control Module’ --> ’03-ABS Brakes’ but got no response error.
Also tried looking at ‘OBD-II Functions, you guested it, just got a ‘Not Compatible’ error.
Hence the above question; ‘Would anyone know how to manually trigger the ABS Unit (not using VCDS) to cycle the ABS pump to bleed air out of it?’
I did find a reference to specialist, specific bit of Audi ABS diagnostic equipment in the workshop manual a ‘Bosch ASB 2 LED-Tester’, but thought the chances of any garage / person having one of those now, a bit thin on the ground.
---------------------------------------------------
VCDS ABS Bleeding Process
Prerequisite :
2 Mechanics
A pressure bleeding machine with 1 litter of brake fluid minimum
2 Bleeding bottles with none return valves
Hook up your waste fluid bottle to the inner nipple of the Front Left Caliper then open VCDS
Select 03-ABS-Brakes (sometimes a beeping can be heard when connecting to the ABS module)
Click on 04-Basic Settings (some models use Output Tests 03)
Note: Another tread recommends when using Output Tests 03: go to Security Access first and type 40168. If you don't do this bit you can't run any ABS pump tests, (can’t comment on that as didn’t get that far),
When you have entered you security access code you can select Output Tests 03 which will automatically start the ABS test procedure and the ABS light on the dash should start flashing and you'll hear an electrical pump sound
Select "Group 001" and press "GO".
Press down the brake pedal firmly as for emergency braking (but not to the floor)
The ABS pump then triggers itself.
Then connect the bleeding bottle to the front bleeding screws (front right / front left) and open them.
Then click on "next".
The ABS pump starts running and can be heard when performing the bleeding process.
Then press the brake pedal slightly 10 times (do not press the brake pedal all the way down to the floor to avoid damaging the master cylinder).
Close the two bleed screws (end of bleeding process)
Leave the process (Do not click on "next" otherwise the process restart)
After bleeding the ABS module, continue with a normal ABS bleeding cycle:
Front Left / Front Right
Rear Left / Rear right
Bleed approx. 200ml per breaking calliper.
So going slightly mad with this issue.
As it’s the last thing stopping me getting my S2 Coupe restoration MOT’ed and back on the road after more than 20 years of being neglected and stood by the previous owner.
The issue being, it takes 3 pumps of the brake pedal to get a reasonably firm brake pedal!
The first pump go’s practically to the floor.
Second about half way down,.
The third about 20mm travel giving an OK (ish) pedal feel, hold your foot on the brake and it does feel spongey, as if there is air still in the system.
Leave the brakes for 5 minutes and I’m back to 3 pumps to get any kind of brake pedal, the S2 dose stop when driven but doesn’t fill you full of confidence!
This is a long post, I'll cut to the question (the full backstory is below).
Would anyone know how to manually trigger the ABS Unit (NOT using VCDS) to cycle the ABS pump to bleed air out of it on an S2 Coupe?
Any constructive help / advice appreciated
------------------------------------------------------------------
Backstory
Blead the brakes so many times and methods, loosing track.
Blead Calliper’s:
RR --> RL --> FL -->FR
RR --> FR -->RL --> FL
FL --> FR --> RL -->RR
And just about any other permutation of this sequence, with the engine off & running.
Also done old school 2 man pump brake pedal & hold method.
Power Bleed at 20PSI from master cylinder reservoir.
And 20PSI reverse bleed from each calliper back to master cylinder reservoir.
The S2 has had new master cylinder, new vacuum ATE brake booster, refurbished standard S2 callipers front & rear and all new copper brake lines with Goodridge braded hoses.
The only old parts reused were the brake compensator & ABS Unit.
Can’t see any obvious bleed nipples on the brake compensator & ABS Unit.
Have done a load of research on line, this seems to be a common issue with ABS systems in general when any kind of major work has been carried out and generally requires the ABS unit to be cycled/blead with tools like VCDS for example.
So have managed to piece together (from various posts) the below ‘VCDS ABS Bleeding Process’.
Confident I was on to a winner dug out my VCDS HEX V2 with OBD 2 x 2 adapters only to find my 1991 S2 Coupe isn’t listed / supported in VCDS just the 1992 on S2.
Gave it a try anyway, VCDS did pick up some issues, (a good thing I thought as it was talking with the controllers), so tried the ‘Select Control Module’ --> ’03-ABS Brakes’ but got no response error.
Also tried looking at ‘OBD-II Functions, you guested it, just got a ‘Not Compatible’ error.
Hence the above question; ‘Would anyone know how to manually trigger the ABS Unit (not using VCDS) to cycle the ABS pump to bleed air out of it?’
I did find a reference to specialist, specific bit of Audi ABS diagnostic equipment in the workshop manual a ‘Bosch ASB 2 LED-Tester’, but thought the chances of any garage / person having one of those now, a bit thin on the ground.
---------------------------------------------------
VCDS ABS Bleeding Process
Prerequisite :
2 Mechanics
A pressure bleeding machine with 1 litter of brake fluid minimum
2 Bleeding bottles with none return valves
Hook up your waste fluid bottle to the inner nipple of the Front Left Caliper then open VCDS
Select 03-ABS-Brakes (sometimes a beeping can be heard when connecting to the ABS module)
Click on 04-Basic Settings (some models use Output Tests 03)
Note: Another tread recommends when using Output Tests 03: go to Security Access first and type 40168. If you don't do this bit you can't run any ABS pump tests, (can’t comment on that as didn’t get that far),
When you have entered you security access code you can select Output Tests 03 which will automatically start the ABS test procedure and the ABS light on the dash should start flashing and you'll hear an electrical pump sound
Select "Group 001" and press "GO".
Press down the brake pedal firmly as for emergency braking (but not to the floor)
The ABS pump then triggers itself.
Then connect the bleeding bottle to the front bleeding screws (front right / front left) and open them.
Then click on "next".
The ABS pump starts running and can be heard when performing the bleeding process.
Then press the brake pedal slightly 10 times (do not press the brake pedal all the way down to the floor to avoid damaging the master cylinder).
Close the two bleed screws (end of bleeding process)
Leave the process (Do not click on "next" otherwise the process restart)
After bleeding the ABS module, continue with a normal ABS bleeding cycle:
Front Left / Front Right
Rear Left / Rear right
Bleed approx. 200ml per breaking calliper.
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