need advice...post 17z brake install. sticky caliper not fixed...

[spidy512]

Morning AZ friends!

So I finally was able to install the rebuild 17z caipers and JHM 330mm rotors on my car. The install def had its hiccups, but in the end I am pleased with the outcome. I was using the excuse of a sticky caliper on the front left to go ahead with the upgrade. I confirmed the sticky caliper when I removed the old brakes. The FL would not let go of the caliper and they came off the car as a unit. I could always tell when the caliper was stuck by a vibration in the steering wheel and a very stiff brake pedal (no travel, instant engagement).

So the past couple days I noticed the stiff pedal feel and the vibration around 60-65mph (although not nearly as bad as the old brakes). The LF rotor is also noticeably hotter after my commute to work. It is somewhat random as well.So now my thoughts are possibly the following;

1. I was unlucky and have another sticky caliper and it just happen to be on the same side as before, with newly rebuilt 17z.

2. Possibly I have a brake booster/ABS issue? The abs light has always come on randomly, and I have not pulled the code. I have read the brake booster can fail as well, and improperly apply pressure.

Has anyone had similar issues? Or can anyone provide insight?

Thanks in advance!

Josh

[rollerton]

Might be obvious..but Brakes lines? The rubber brake lines can corrode internally and not allow pressure to return back through the line, causes the caliper to stick.
Simple test is to swap the brake lines left to right, bleed, drive, see if it still sticks.

[Milehi]

Might be obvious..but Brakes lines? The rubber brake lines can corrode internally and not allow pressure to return back through the line, causes the caliper to stick.
Simple test is to swap the brake lines left to right, bleed, drive, see if it still sticks.

Yep, I'd check the lines before anything else. Had that happen on a porsche I had years ago.

[julex]

I think the lines have to be upgraded for 17z anyway? You can't just bolt stock lines to the calipers.

I would look at new abs unit, it's proportioning valve(s) are shot, obviously.

[spidy512]

Thanks for the replies!

I replaced the brake lines with stop tech ss (rs4) so I think I am good there.

Thanks julex. The more I research the more it looks like the abs unit. Bummer.

Josh

pS. Of course the brakes worked fine on the drive home...ha

[julex]

Thanks for the replies!

I replaced the brake lines with stop tech ss (rs4) so I think I am good there.

Thanks julex. The more I research the more it looks like the abs unit. Bummer.

Josh

pS. Of course the brakes worked fine on the drive home...ha

What car you have? So it happens I ended up with brand new ABS unit that fits A6/Allroad and perhaps more C5s but I would need specifics... it won't be used ebay ABS unit price though but nothing approaching dealer prices even remotely I think they value these at $1500 lol.

[bengone1]

Only one front brake sticking would cause pulling to one side. Master cylinders can cause this as well. If you are not having pulling, your opposite side rear brake is also engaged. Check temps of the rear rotors as well.

[spidy512]

More info....

Car is a 2002 S6.

Today me and the wife drove down to South Lake to pick up my repainted euro S6 bumper from Rory. I noticed on the way home the brakes were dragging as described in my initial post. I stopped at one point and checked the rotor temps. Left front and right rear were unusually hot. But not sper bad. The other two were barely warm.

I gave the pedal a good solid slow push and that seemed to relieve the pressure at the brakes. When I got home the rotors were cold at all four corners.

Does that make sense to anyone? thanks bengone1 for the tip on the rear as well? Does that point to the abs unit?

Thanks again!

Josh

Almost forgot...the car does not pull excessively in either direction.

[julex]

it is abs unit's valves acting up. NExt time you have your car cold, start driving without applying any brakes (use hand brake to get out of driveway) and try to do as much as possible without applying brakes, pull into any parking lot and check rotor temp. If any is warmer than the other, then you have sticky calipers, if none nothing is sticking but the ABS once you brake normally.

[spidy512]

Thanks julex!

Quick question. Can I just pull the abs fuse or unplug the ABS unit so it does not engage? Thanks again for the help!

Josh

[julex]

Maybe, depends. If the valve is sticky then that won't make much difference as it stick on its own volition, not because module tells it to.

[Herb5998]

Had a similar issue with my S6, lots of different attempts to solve it, but in the end, it was the brake booster/master cylinder unit. Since then, no issues.

[bengone1]

I would say replace the brake master cylinder first. VAG products have had dual diagonal braking systems forever. A clogged return port on one chamber of the master will cause these symptoms exactly. A sticking valve in the ABS unit is more likely to cause dragging on one wheel. Even if I am wrong and you waste $150 on a master cylinder you will be a lot happier than replacing the ABS unit to find out it is the master cylinder.

[spidy512]

Thanks for the addition replies!

I am going to try the master cylinder first I think. Yesterday on the way home it seemed as though all four wheels were hotter than normal.

Not sure if this is helpful, but this AM when I was trying my "push to the floor to unstick the maybe sticky ABS" and it seemed the pushrod for the booster seemed to return slowly. Like it clunked up against the pedal after I let off the pedal quickly. So it made me think possibly the booster is stuck as well. Not sure if that makes sense, but that was what it felt ike. The brakes were still stuck this morning, the front left and rear right.

Thanks again for the help y'all. I love this place....

Josh

[julex]

Yeah, do booster and master and report back.