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rockbeau25
05-22-2018, 02:42 PM
Recently upgraded my B5 A4 to D2 S8 (same as Porsche 993tt) calipers, with B5 S4 rear calipers. I also replaced lines with braided lines. After I got it all put back together, I bled the brakes but when I started the car the pedal went right to the floor. I bled them again and same thing. By the third time, there was some feeling but nothing significant. Each subsequent time after that there was more feeling till about the 5th or 6th time when it didn't seem to be getting any stiffer. I bled both with a pressure canister and normally. The car is to a point where its driveable but not very confidence inspiring. I can manually pump the brakes while I'm driving to give them more feeling but it goes away if I'm not constantly on the brakes. There are no brake fluid leaks.

There are two things I am thinking it could be but I am no expert and am not sure if either of them really make sense. The first idea I had was the ABS needs to be bled. I've read conflicting things on this. Some people say never bleed ABS unless you're swapping ABS components. Others says its possible to get air in the ABS lines regardless. To my understanding, this is just a simple vag com procedure after the brakes have been bled.

My other idea was the master cylinder. I've again read conflicting info on this. More pistons means more fluid to push which makes me think I just need to upgrade the master cylinder. However, I read that the A4 master cylinder is good up until 18Zs, which my BBK is much smaller than.

So do I keep bleeding them until I have more feeling, ABS bleed, or upgrade the master, or something I'm missing altogether?

Loserface
05-22-2018, 04:21 PM
Same thing happened to me on a Jetta years ago. Bled and bled and bled the brakes, but could never get a firm pedal. Did the ABS pump bleed procedure with VCDS, and pedal was restored. If you have access to VCDS, definitely try bleeding the ABS pump.

fR3ZNO
05-22-2018, 05:22 PM
I would say keep bleeding. Drive around a bit and bleed a few times. But to some point you will have a softer pedal/longer travel because of the larger caliper pistons.

Rodgman15
05-22-2018, 07:13 PM
I just installed 17zs and didn't have to run the abs pump fwiw

Also, if they have twin bleeders on the calipers, start from the outside and work your way in when bleeding

rockbeau25
05-22-2018, 07:37 PM
I just installed 17zs and didn't have to run the abs pump fwiw

Also, if they have twin bleeders on the calipers, start from the outside and work your way in when bleeding

Does your pedal feel any different? Softness or travel?

Rodgman15
05-22-2018, 07:41 PM
Initially it was soft, went to the floor if you didn't pump it a few times. I too was under the assumption I had to cycle the abs pump, but after a second bleeding it straightened right out.

Rock hard throw you through the windshield type shit now.

rockbeau25
05-22-2018, 07:44 PM
Thatís how mine are if you pump them, and if I donít pump them itís still that way but a really long pedal, almost as long as the clutch. Ideally I could get that same feeling without such a long pedal :)

canadianA4B7
05-22-2018, 08:19 PM
Have you disconnected battery to open any types of solenoids? Possible thereís a pressure loss solenoid that would close to maintain 1 set of brakes. Remove batt leads tap them to each other and try bleeding again. You may have only pressurized to the solenoid.

rockbeau25
05-22-2018, 08:21 PM
Have you disconnected battery to open any types of solenoids? Possible thereís a pressure loss solenoid that would close to maintain 1 set of brakes. Remove batt leads tap them to each other and try bleeding again. You may have only pressurized to the solenoid.

I had the battery disconnected throughout the brake job. Reconnected before I bled them.

kwnk
05-22-2018, 08:29 PM
Try bleeding again. Did you start at the caliper furthest from the reservoir?

1- Right-rear brake caliper
2- Left-rear brake caliper
3- Right-front brake caliper
4- Left-front brake caliper
5- Clutch cylinder (if manual)

And x2 may have to run VCDS to bleed ABS:
I think the procedure is this: (I'll test on my car later to verify)


03 - ABS Brakes
04 - Basic Settings
002 - Runs the ABS Pump

Take note: do not try move up to 003 in Basic Settings: You enter into a very annoying brake test mode that's a pain in the *** to get out of.

Or a manual way to bleed the module is to make a couple ABS stops on the street [>_<]

Are you using a pressure bleeder?

rockbeau25
05-22-2018, 08:33 PM
Try bleeding again. Did you start at the caliper furthest from the reservoir?

1- Right-rear brake caliper
2- Left-rear brake caliper
3- Right-front brake caliper
4- Left-front brake caliper

And x2 may have to run VCDS to bleed ABS:
I think the procedure is this: (I'll test on my car later to verify)



Or a manual way to bleed the module is to make a couple ABS stops on the street [>_<]

Yes, I bled this way until it stopped having a noticeable difference. Iíll definitely try ABS next. If that does nothing I guess Iíll just keep bleeding. Kind of annoying though cause Iím not getting any bubbles and it seems like Iím just pushing clean brake fluid in and out of the system...stuff isnít cheap either. My friend just did 17Zs on a Jetta and said it took over 10 bleeds to feel normal. Maybe thatís all there is to it but it certainly seemed like it stopped making a difference for me.

canadianA4B7
05-22-2018, 10:11 PM
I had the battery disconnected throughout the brake job. Reconnected before I bled them.

That could have caused the scenario Iím talking about. The fluid pressure would be 0 when initially connecting 12V if then you depressed the peddle to bleed the brakes I could only assume the system sensed no pressure or rears and closed any sort of safety solenoid.

Try bleeding with battery disconnected.

coolgraymemo
05-22-2018, 10:48 PM
I've done four or five BBK installs/removals and have always gotten away with simply bleeding the front brake calipers. I've never had to cycle the ABS.

Most recently on my B5/S4 with 18Z calipers, all I only bled them a few times and the brake pedal feels similar to it did when I had HP2s.

walky_talky20
05-23-2018, 04:24 AM
I think you probably have some air trapped somewhere, probably the ABS block. You can run the ABS pump with VCDS and see if that helps, but on troublesome bleeds it can help to bleed the brakes in the opposite direction. What they call "reverse bleeding", where you push fluid in at the caliper and the air goes up into the reservoir. You can do a mild version of this just by compressing all the caliper pistons. Sometimes that's enough.

rockbeau25
05-23-2018, 05:39 AM
I think you probably have some air trapped somewhere, probably the ABS block. You can run the ABS pump with VCDS and see if that helps, but on troublesome bleeds it can help to bleed the brakes in the opposite direction. What they call "reverse bleeding", where you push fluid in at the caliper and the air goes up into the reservoir. You can do a mild version of this just by compressing all the caliper pistons. Sometimes that's enough.

Is the ABS bleed as simple as cycling the pump with the vag com or do I need to do anything in addition to that?

walky_talky20
05-23-2018, 06:14 AM
Just run the pump a bit, then bleed again.

Creechy
05-23-2018, 09:31 AM
I had to bleed the rear's lots for time's when I installed S4 rear calipers. Mine are on a Fwd so they're technically upside down compared to a Quattro but I just lift them off the disc and bleed with a wind back tool against the piston.

PZ.
05-23-2018, 11:52 AM
Almost hate to ask, but are the front bleeders on top of the caliper? It happens....

rockbeau25
05-23-2018, 11:53 AM
Almost hate to ask, but are the front bleeders on top of the caliper? It happens....

They're on top, yeah

Joe Jr.
05-23-2018, 03:10 PM
i'm thinking id agree with walky...there's air somewhere...like you haven't figured that out, but i think you can eliminate the MC being the issue. I would also challenge that even though there are more pistons in the new calipers, are they actually more overall piston area than stock? Maybe, but not necessarily.

rockbeau25
05-23-2018, 03:58 PM
Well guys my game plan will be abs bleed with my vag com then re bleed with the battery disconnected, kill two birds with one stone right?

rockbeau25
05-23-2018, 09:17 PM
Havenít had time to do a bleed so I did kwnkís abs bleed method lol. Seemed to help somewhat but Iím guessing thereís some placebo there.

seanf86
05-24-2018, 07:23 PM
are the calipers old or have been sitting for a long time? I had this problem on an old car where the pistons were rusty and the seal wouldn't slid on the piston so as the piston came out it stretched the seal and when you let off the brake it pulled it back so I had a ton of pedal travel, new calipers solved my problem.

rockbeau25
05-24-2018, 07:32 PM
are the calipers old or have been sitting for a long time? I had this problem on an old car where the pistons were rusty and the seal wouldn't slid on the piston so as the piston came out it stretched the seal and when you let off the brake it pulled it back so I had a ton of pedal travel, new calipers solved my problem.

Theyíre used but I rebuilt them prior to install.

FilAlleva
08-03-2018, 06:41 PM
I seem to have a problem that may be related to this thread. During my last track day I started developing a spongy pedal after hard braking - I had attributed this to the ABS kicking in. It got really uncomfortable flying into a corner, first with good brakes and then sponge city. The consensus at the track was bleed your brakes - you boiled the fluid (660!) - so sure enough there was air in the system and the brakes felt firmer. But still I was under the impression that if the ABS kicked in the pedal feel would go away. The next day with a completely cold system I decided to test my theory that ABS would lead to a soft pedal - so I went and did a hard enough stop so the ABS would engage and sure enough I got the same sickening feel of the long soft pedal. So now I'm thinking I have air in the ABS Module. Not sure if I'm on the right track. I'm thing the ABS system got air trapped in the pump and when activated it made the brakes spongey. Guess I'm going to try the VCDS pump flush. As to how this happened - I'm clueless. The last fluid flush was done by a very reliable shop.

walky_talky20
08-03-2018, 08:04 PM
Yep. Sounds like you are getting a little more air out of it every time kick the ABS in. Bleeding with vcds should do the magic for you. Good Luck.