Hi guys,

I am currently in the process of changing the rear discs and pads on our Roomster.

Disassembly has been ok.

I have hit a bit of a snag with rewinding the piston. It doesn't seem to be winding in fully. The piston is not loose, yet it keeps turning when the Tommy bar goes clockwise. It comes out when going anti clockwise, so I'm fairly certain that it's being turned the right way.

If you loosen it, it gets loose, then clockwise will get it tightened so far, but it stops winding in yet it keeps turning. Not sure I explained that very well!

Any advice on how to get it fully in?

There is a nut behind it on the caliper. Does this need to be held firm as you wind to get it fully in? Otherwise, I'm stumped!

I would try just now, but the darkness has gotten the better of me.

Photo included.

Thanks in advance,

Joe.

17 minutes ago, joeninho said:

I have hit a bit of a snag with rewinding the piston

Are you using a Brake caliper wind back tool?

If so, with a Left hand thread or Right hand thread?

Thanks. AG Falco

Hi AG,

Yes, I am using a brake caliper wind back tool, although I do feel like a bit of a muppet in that I am not sure of the answer to your second question. It has two Tommy Bars with it and various fittings. Currently in the garage awaiting tomorrow's attempt!

I just grabbed one of them and used it as it seemed to tighten the piston, although only in a limited sense, as mentioned above.

Thanks,

Joe.

You need to use a wind back tool, it needs to be the correct "handing" although my RH standard one has always worked on Fords and VAG.

As the piston rotates you must also maintain an axial force by undoing the knurled adjusting sleeve.

Hard to describe but it should make sense with the tool at hand.

26 minutes ago, joeninho said:

Yes, I am using a brake caliper wind back tool,

Look at this:-

Thanks. AG Falco

43 minutes ago, AGFalco said:

Look at this:-

Thanks. AG Falco

Dude, this is almost exactly the kit I have, although I grabbed a bar at random and I wasn't using the fixing plate part, which made it a huge pain in the ass.

Hugely helpful. Thank you!

J.

Edited 7 March, 20251 yr by joeninho

1 hour ago, J.R. said:

You need to use a wind back tool, it needs to be the correct "handing" although my RH standard one has always worked on Fords and VAG.

As the piston rotates you must also maintain an axial force by undoing the knurled adjusting sleeve.

Hard to describe but it should make sense with the tool at hand.

JR, at the risk of sounding like a numpty, how would I identify the knurled adjusting sleeve?

Cheers,

J.

The missus is hoping she'll be driving this to work on Monday...

I'm displaying supreme confidence...with you guys in the background!

5 minutes ago, joeninho said:

JR, at the risk of sounding like a numpty, how would I identify the knurled adjusting sleeve?

The one in the video does not have one and is not a good tool IMO, probably due to it having to be universal.

This will be difficult to explain but the helix on the caliper piston adjustment screw is a coarser thread than the screw on the tool so as the piston is rotated and screws itself in the drive plate on the tool becomes loose, the contra threaded sleeve on my tool allows me to maintain the axial pressure, if I have not pre-loaded it enough at the start then sometimes the piston will turn but not retract on its adjuster locking the tool up.

Others with experience of that universal tool may say it isn't a problem, if thats the case disregard my comment.

Edited, ignore the above, I had only skimmed through the video as it was so long and wordy, right at the end you can see him taking up the slack by turning the large hexagon by hand, on mine it is knurled so easier to do, you need to regularly take up the slack when using the tool which he does not mention.

Edited 7 March, 20251 yr by J.R.

7 minutes ago, joeninho said:

how would I identify the knurled adjusting sleeve?

In the video that tool is not knurled.

If you look at the still from the video it is the part just in front of his right index finger.

With the hexagonal end that the long threaded part goes through.

THT

Thanks. AG Falco

I'm sure I've only ever used the RH windback tool on VAG models. either side is clockwise to wind in from memory, never had any bother using the same set as above.

The Transit brakes I did last weekend were opposite on either side but they did have an arrow on each casting to tell you the direction it wound back in which was nice.

Still struggling, guys.

Can't get the plate for the rewind tool in to use it properly due to there not being enough of a gap between the piston and the caliper.

Any ideas?

You can probably get it started in the right direction with a bit of rough improvisation. Use a pair of water pump pliers to wiggle the pot round a bit, give it a tap inwards with a little hammer and a bit of wood, or a squeeze with the windback with the adaptor taken off. Take baby steps, and repeat at length. If that doesn't work, try applying slight pressure with the windback took as you wiggle the pot round.

The alternative is a wind back tool that's meant for these calipers only, so you should get a bit more clearance to get the tool in with not having to use an adaptor.

Edited 8 March, 20251 yr by StevesTruck

Remove the plate, preload the adjusting screw with a G clamp, wind the piston in a little then use the plate.

Were the pads worn through to the backing plates or did you press the brake pedal when the caliper was removed?

a better method is to preload the piston with the G clamp then screw it in a little using water pump pliers.

Thanks, JR.

What do you mean by preload the piston with a G Clamp?

I do have a G clamp. Just not sure where to put it.

Edited to add that I haven't touched the brakes since starting the job.

Yes, I think the pads were worn through.

Edited 8 March, 20251 yr by joeninho

Still no progress on LHS.

This is what the RHS looks like with everything removed.

Is that piston already wound in enough?

Edited 8 March, 20251 yr by joeninho

Changed the RHS without issue after winding the piston in a bit.

Still stumped on LHS. The piston just keeps turning but not going in. Must have done hundreds of revolutions.

One side of our handbrake doesn't work.

Would that have any effect on this?

Edited 8 March, 20251 yr by joeninho

3 hours ago, joeninho said:

One side of our handbrake doesn't work.

Is the handbrake off?

Thanks. AG Falco

Good point!

Success! Managed to change both sides.

Some serious brute force was required to wind the rear left piston in.

If anyone encounters the same problem, it helps massively to attach the caliper back on with the screws tightened a bit. This keeps the piston fixed on one place, which allows you to really apply some force when rewinding it. Once the piston was on a bit, I then had enough space to use the rewind tool.

Huge thank you to all of you for your help! Greatly appreciated.

J.

P.S. The brakes are not working properly unless you pump them a few times, so I guess it's time to learn how to bleed the system.

2 minutes ago, joeninho said:

P.S. The brakes are not working properly unless you pump them a few times, so I guess it's time to learn how to bleed the system.

Plenty of WD-40 on the bleed nipples for an hour or so before you need to unwind them a bit.
Two people on the job makes it quicker IMO. Unless things have changed drastically then work from the brake furthest away from the brake fluid reservoir to the closest.

Edited 8 March, 20251 yr by Lee01

33 minutes ago, joeninho said:

If anyone encounters the same problem, it helps massively to attach the caliper back on with the screws tightened a bit.

I forgot to mention that, I secure them with the one caliper bolt allowing it to swing out to access the piston.

If the pistons are relatively free then they can be held by hand.

Nothing you have done will have let air in the system, you will need to pump the pedal initially, then as the pads bed in the pedal will become firmer.

If you have a problem with the handbrake self adjuster on one or both calipers attend to that before bleeding the brakes, look at the lever compensator, it should be normal to the cable axis, do not adjust the slack cable before ensuring the self adjusters are working properly. With the handbrake pulled up hard both caliper levers should make the same angle, critically they should both return to the same angle when the handbrake is released.

Return springs were fitted to the levers on some models, these can be fitted to others to help if everything else is free.

I think it was "longer" cars that had return springs fitted as standard when using these callipers, many people, including me, have retro fitted what were originally VW Sharan rear calliper external return springs either to improve things, as on my wife's previous 2002 VW Polo, or at least in my case, bought a new pair of springs and fitted them to my wife's next car - a 2015 VW Polo, and fitted them when the car was brand new, just to make sure that the rear brakes never ended up dragging - though I reckon that at some point, these callipers ended up being fitted with "more suitable" internal return springs, but I've stuck with fitting external return springs.

Note:- these alloy callipers will normally end up seizing due to a build up of probably aluminium corrosion ending up on the chromed steel surface of the piston - and that is enough to cause them to jam/seize. That is probably why you had trouble winding that piston back in, ie you have forced the junk back through the sealing ring, I think that I've got away with doing that in the past, on my wife's 2015 VW Polo, the RHS calliper seized and I had to get the car back on the road quickly, so just bought a refurb'd calliper via Halfords (supplied by ECP, a Pagid part). I should really have by now, removed and serviced the LHS including fitting new seal and dust cover, and maybe this summer that will get done, as by my reckoning, once one side has seized, the other side must be getting close to being the same!