Brake bleeding and ABS

[-DK-]

Just did my first pad and rotor change on my GTI. My pedal travel is fairly long and spongy. I used the motive power bleeder and followed the LF, RF, LR, RR sequence. I’ve bled many cars and haven’t really had this issue. I’m assuming air go into the ABS system. I bled at 15 psi per the motive instructions and bled until fluid was clear and without air bubbles. I’ve seen references to bleeding at 30 psi, doing hard ABS stops or cycling the abs pump via OBDeleven or VCDS. what’s the most direct route towards a firm pedal? Thanks

 

[scrllock]

The service manual calls for first bleeding at 29psi, starting out with both fronts, then both rears at once. Then the same bleed you did, again at 29psi. Then if the pedal is still spongy it calls for a standard pedal bleed followed by a hard ABS stop.
I just did the standard flush with 29psi at each corner in succession and pedal felt fine.

 

[-DK-]

The service manual calls for first bleeding at 29psi, starting out with both fronts, then both rears at once. Then the same bleed you did, again at 29psi. Then if the pedal is still spongy it calls for a standard pedal bleed followed by a hard ABS stop.
I just did the standard flush with 29psi at each corner in succession and pedal felt fine.

So you crack both front bleeders simultaneously, then the rears simultaneously?

 

[scrllock]

 

[-DK-]

Interesting. I’ve never done that before. I’ve also always started furthest brake from the MC. I’ll try this at 29psi also. Thanks for pointing me in the right direction.

 

[anotero]

View attachment 233332

Where can i get this version of the service manual?

 

[FSTSNAL]

Where can i get this version of the service manual?

Erwin. Pay for a 1 day license and download the manual. It takes a while because it is by section. Also download the full wiring diagram as well. Super handy when troubleshooting intermittent issues.

 

[anotero]

Erwin. Pay for a 1 day license and download the manual. It takes a while because it is by section. Also download the full wiring diagram as well. Super handy when troubleshooting intermittent issues.

Got a subscription late last night.
Thanks for reminding me of the wiring diagram.

 

[YamR1rider]

Was at a bit of a loose end today so decided to bleed some new fluid through my PP brakes (even though I only did it last a year ago) and decided to see if there was anything I could do to get a bit firmer pedal.

First of all went for a quick run out to trigger the abs a few times to make sure fluid had moved through there. Then came back and busted out the trusty motive power bleeder 'black label' version (with the screw on Aluminum cap, much more secure ) and put one liter in. I usually go at 15psi but with talk around the forum at the mo pumped it up closer to 30. Bled roughly 200ml through each caliper, no signs of bubbles anywhere (which was to be expected as being a life long biker I'm a bit particular about brake bleeding and as mentioned, only did it last a year ago). I will say that it seems 30psi is better than 15 on these cars.... I have noticed previously when using the lower number you have to crack your bleeder screws more to get the fluid to move and even then the whole process is slower (and maybe, cracking the screws more raises the potential of air around the threads?).

I normally stop there and call it good, but this time, got daughter to press the pedal with the bleeder still attached and went round each caliper again for a confirmatory bleed. Given I was getting a bit low on fluid only did a couple of pedal pumps per caliper.

Just took the car out and had a quick go and I do think the pedal is a little firmer and shorter. Could be just fresh fluid I guess, or maybe the combo of higher pressure and quick confirmatory old style pedal pumps has helped a bit.

 

[scrllock]

the service manual doesn't have you use 29psi for laughs. it helps a lot.

 

[YamR1rider]

Well....given a full, already pretty well bled system and all you are doing is bleeding through the old fluid for new, the only difference 29psi really makes is pushing the fluid through quicker, especially to the rear calipers. I think that the stated 29psi (and total full process, as per the manual) is really for a new bleed following an air-introducing job such as calipers off or otherwise emptying the braking system, and when you need to cycle and get air out of the ABS valve.

 

[Autobahn]

Good fluid helps with minimizing compressibility too. I always start with the shortest line from the ABS (passenger/front). When I recently installed my Brembo kit I was able to get full brake engagement within the first 1/8 travel.

I used my power bleeder for the first time at 20 psi and no fluid in it (dry method) and barely any fluid would come out of the rears. I’ll try 29psi next time. I always complete my bleeds with a pump/hold method which produced some more air out of the fronts.

 

[.James]

The service manual calls for first bleeding at 29psi, starting out with both fronts, then both rears at once. Then the same bleed you did, again at 29psi. Then if the pedal is still spongy it calls for a standard pedal bleed followed by a hard ABS stop.
I just did the standard flush with 29psi at each corner in succession and pedal felt fine.

Hey I'm wondering why you are saying to bleed all the brakes twice. Is this instruction for everyone or just the other person you were replying to?
Also how do you bleed 2 calipers simultaneously as the manual says? Thanks!

 

[scrllock]

Hey I'm wondering why you are saying to bleed all the brakes twice. Is this instruction for everyone or just the other person you were replying to?
Also how do you bleed 2 calipers simultaneously as the manual says? Thanks!

Like I said, if it's still spongy, it calls for a second bleed.

You hook up two bleeder bottles and loosen both of them with the power bleeder pressurized. A second person is handy but if you can get both wheels in the air it's not an issue. This would require 3 people if you didn't have a pressure bleeder.