Hi folks,

I'm in the middle of replacing the rear discs and pads on my 2019 1.5 Scala.

I am under the impression that the piston needs to be wound back into the caliper as a post to just pushed in.

I'm winding it back in but it doesn't seem to move. Am I just turning the piston in the caliper or is it just very very slow to retract?

Thoughts.

Cheers

Happened to me on the Golf I owned previously. Turned out to be due to there being a 'load apportioning valve' in the rear hydraulics which shuts off the hydraulic circuit if the wheel is down. If you have the car jacked up then this may be the cause, because the hydraulic fluid is blocked from returning to the master cylinder.

I solved it by attaching a pipe to the bleed valve and opening the valve before winding back.

One other thing - the cylinders on the Golf had a left hand thread. Took me a while to work that out☹️

Edited 24 July24 Jul by Biscayne
additional information

It transpired that I was using the tool is bought to wind the piston back in incorrectly. There is a plate that I should have been using and this goes on the tool to hold things in place. I just didn't do that.

In my defence, it's the first time I've done rear brakes on such a new car. Normally on front ones, I've just used a clamp to force the piston back in but I knew that I had to use this tool to turn the piston back into the caliper. It didn't help that it was quite cramped where I was working but I've sorted it now.

A lesson for others replacing rear pads/discs.

2 hours ago, cwt said:

There is a plate that I should have been

You still should be able to wind it back if piston is not rusty and seal not swollen. Open the bleeder.

2 hours ago, cwt said:

Normally on front ones, I've just used a clamp to force the piston back

Do not open bleeders guys and in 100 times nothing will happen and 101 time you will damage ABS pump like I probabbly damaged mine.

I opened the master cylinder to take account of fluid being forced back up the lines. The level did rise but not a lot.

I never thought about opening a bleed nipple.

All seems ok as I've driven a few miles with the new pads and discs. I'm happy.

Normally you can get a lot better access if you remove the handbrake cable and unclip a couple of brake pipe clips.

I might e wrong, but I think that in the past, I've temporarily fixed the removed calliper back to the calliper carrier by using the bottom calliper bolt hole fitted into the top calliper carrier guide pin - to help with keeping an troublesome calliper in control while fighting with the piston retracting - I think that I've even resorted to slightly moving the handbrake lever when a piston could not be rotated easily - at first.

1 hour ago, rum4mo said:

Normally you can get a lot better access if you remove the handbrake cable and unclip a couple of brake pipe clips.

I might e wrong, but I think that in the past, I've temporarily fixed the removed calliper back to the calliper carrier by using the bottom calliper bolt hole fitted into the top calliper carrier guide pin - to help with keeping an troublesome calliper in control while fighting with the piston retracting - I think that I've even resorted to slightly moving the handbrake lever when a piston could not be rotated easily - at first.

I decided to leave the hand brake cable alone, but did reattach the caliper as you say.

It really does make life easier if you remove the handbrake cable - just flick it out using a screwdriver, clean the lever and grease it and the ball end of the cable - I do this every 2 years when I service/clean the brakes.

The handbrake cable can then be removed from its mounting on the calliper, so apply a bit of "squeezing" effort to its locking sleeve and push it back out of its mounting.

Just my suggestions for the "next time".

21 hours ago, cwt said:

fluid being forced back up the lines. The level did rise but not a lot.

this way dirty fluid behind the piston goes back to ABS pump against pump filters. In this circut pressure from calipers is nor normal operation.

You were lucky 😊

21 hours ago, cwt said:

I never thought about opening a bleed nipple.

Well you help bleeders to weld with caliper forever 😉

38 minutes ago, kokosal said:

Well you help bleeders to weld with calliper forever 😉

Changing the fluid every 2 years stops that happening.