T6.1 Brake Bleeding Problem

[DXX]

i had the van in getting the calipers painted. i don’t know what they’ve done but they can’t get pressure into the system, pedal keeps dropping to the floor

Then whoever did the work has a problem to fix.
Hopefully they didn’t use any aggressive chemicals that could have degraded the caliper piston seals.

 

[paxter]

yeah i thought so, they’ve had the van 8 days now. i’m hoping we have progress today

 

[paxter]

still no progress, apparently even vw master technicians are bamboozled with this one. i just want my feckin van back and working.

 

[DXX]

still no progress, apparently even vw master technicians are bamboozled with this one. i just want my feckin van back and working.

Assuming the fluid is at the correct level, isn’t leaking externally and air has been bled out.
A quick check would be to plug the discharge ports on the master cylinder and check if pressure can be raised.
If no pressure can be raised on the master cylinder then the master cylinder piston is either passing fluid internally or the master cylinder is leaking fluid in to the servo.

If during the caliper painting process air was allowed into the ABS unit the whole system needs to be flushed and bled.

I’m wondering if a pressure bleeding tool has been operated at too high pressure and has damaged the master cylinder seals????

 

[paxter]

master cyclinder does seem the obvious choice, I'm getting exasperated at this stage, just want my van back on the road!

 

[DXX]

master cyclinder does seem the obvious choice, I'm getting exasperated at this stage, just want my van back on the road!

It’s very easy to test, no need to guess. No idea which garage you are using but I don’t recommend using them again.

 

[AVR2]

i had the van in getting the calipers painted. i don’t know what they’ve done but they can’t get pressure into the system, pedal keeps dropping to the floor

I've found this thread after Googling - did you ever find out the problem? I've got the same issue on a 2008 Golf after changing a seized rear caliper. I've pumped so much brake fluid through all the calipers with no sign of any air bubbles (plus I've run the ABS pump using VCDS), but I can't get a good pedal with the engine running. I've previously changed front calipers with no issues at all.

This seems to be a common VW issue that's mentioned on numerous threads on numerous forums, but none of the threads seem to end with an explanation of how the problem with fixed...

 

[Billyjim]

I also have this same issue after changing front pads, has anyone found the solution ?

 

[AVR2]

I also have this same issue after changing front pads, has anyone found the solution ?

I can't help with the front calipers as I've never had any issues when replacing those, but I've fixed my rears.

I went back to the VW factory procedure and picked up on something I'd completely missed before - VW states that the rear calipers, and the rears only, should be bench-bled before installation (it even states that new VW-sourced rear calipers are supplied pre-bled). The caliper should be oriented with the brake line port facing upwards and the fluid fed in through the bleeder screw until air bubbles stop coming out of the main port.

I tried this, and holy crap it worked.