Brake bleeding problems, rear caliper replacement

I can't see to get the system bled and I'm wondering if there is something I am missing here.

I replaced both rear calipers. I did not fill (bench bleed) them prior to putting them on the car. I did let one the right rear caliper sit empty but on the car with everything closed for a day. Bled the system the first time, getting no air on the hose on the bleeder for at least 5 pulls. Same thing on the other caliper. Went to roll the car and I have no brakes till the last inch or so before the pedal hits the floor and they're very weak when they do come on.

I've bled brakes on cars and bikes in the past so I know I'm doing it right. There's a chance the master was dry and sucked air in, but only a slight chance. The first time I put fluid in I put a lot in but I remember seeing fluid in the reservoir so I'm reasonably sure that didn't happen.

The only things I can think of here are air trapped somewhere in the calipers. Could there be something else I'm missing here?

The rear callipers can be a pita to bleed on the Mk4, I replaced both my rears at the same time and also had a hassle bleeding them properly.
I use a pressure bleeder and while I had that connected I gave the calliper a good dunt with a hard piece of wood while bleeding, that seemed to help release trapped bubbles in the actual calliper.
Once I had eventually got all the air out I still felt the pedal travelled to far till one day when I parked on a really steep hill. I had to pull the handbrake up really hard and it travelled pretty far but after my brake pedal felt loads better and the handbrake stopped having as much travel.
It must adjust them up or something.

There is something in the manual about pre-bleeding them... and also something about holding them at some strange angle for bleeding them.

sorry I don't have access to better information at the moment. My point is that yes, there is something unique about bleeding these - maybe one cannot just put them in empty and bleed them on the car.

You need to bleed the ABS first, with a scan tool. Then if you loosen the bottom caliper bolt, and tilt them UP just slightly (not so much that the piston comes off the pad) they will bleed better.

But the ABS module needs to be accessed first, to purge the air out of there.

It also depends on the amount of fluid that leaked out in the change. I've seen many where they were never done and they get corroded in the lines. You need to pressurize from the top end and STAND on the brake pedal to push it through.

oilhammer said:

You need to bleed the ABS first, with a scan tool. Then if you loosen the bottom caliper bolt, and tilt them UP just slightly (not so much that the piston comes off the pad) they will bleed better.

But the ABS module needs to be accessed first, to purge the air out of there.

Click to expand...

He didn't run it dry so no need on the abs stuff, I also clamped my flexis at the rear but yeh, they're just a pita to get all the air out.

Seatman said:

He didn't run it dry so no need on the abs stuff, I also clamped my flexis at the rear but yeh, they're just a pita to get all the air out.

Click to expand...

You need to use the ABS system to bleed the service brakes. It is in the Basic Settings.

Seatman said:

Once I had eventually got all the air out I still felt the pedal travelled to far till one day when I parked on a really steep hill. I had to pull the handbrake up really hard and it travelled pretty far but after my brake pedal felt loads better and the handbrake stopped having as much travel. It must adjust them up or something.

Click to expand...

When replacing the rear pads, the piston needs to be screwed back. After everything is back together, you need to excercise the parking brake a bunch of times to readjust, and take up the slack in the rear brakes. When the slack is taken up, and your parking brake is tight, you're good to go.

It's the regular use of the parking brake that keeps the rear brakes properly adjusted.

well, I turned the pistons out on the caliper to get the piston set in its position better and it's drivable again.

mattg said:

well, I turned the pistons out on the caliper to get the piston set in its position better and it's drivable again.

Click to expand...

But, the pedal bleeds down a bit with heavy but gradual pressure but not so much when you stab the pedal.

guess I've never noticed before. Is that booster or master?

oilhammer said:

You need to bleed the ABS first, with a scan tool. Then if you loosen the bottom caliper bolt, and tilt them UP just slightly (not so much that the piston comes off the pad) they will bleed better.
But the ABS module needs to be accessed first, to purge the air out of there.

Click to expand...

Have you done this????

oilhammer said:

Have you done this????

Click to expand...

No, I did not bleed the ABS since I'm reasonably sure I didn't let the master run dry.

I did tilt the calipers and move them around and got a tiny bit more air out.


Do you HAVE to bleed the ABS to do any brake bleeding even if there's no air in the system?

Do the Basic Settings bleed of the ABS system, and go through the Output Test a couple times, then rebleed the brakes like normal. It will make a difference. I improve the feel of many cars' brakes simply by doing the Output Test. That car should have EXCELLENT brakes. Minimal pedal travel, minimal effort, good stopping power, no spongy or fading pedal.

I am a little confused. ABS pump bleeding is not required if air is not introduced to the ABS pump says ross-tech but suppose it couldn't hurt...
http://www.ross-tech.com/vag-com/cars/absbleeding.html

Handbrake level on brake calipers

I prefer a pressure bleeder, you can make one from a cheap garden sprayer for less than $20 and it's the best way available. Just need to make a plug for the master cylinder that mates to the sprayer

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