2002 9n rear brake caliper piston not moving

[littlepolo]

Attempted to change the rear discs and pads on my 2002 9n. The rear pads are quite worn and the pad material is approximately half the thickness of the new pads. I found I could rotate the piston using a screwdriver although there was quite a lot of resistance. I was able to turn the piston several times but it did not retract at all. Went and hired a piston tool but it did not seat into the drive on the piston so it was not much help (probably need a better quality tool). I guess the piston might be on a fine thread but surely not that fine. As a result I had to refit the old pads.

So I'm wondering if I just need a better tool (I'd say the piston turned at least 5 or 6 times with no horizontal movement at all. I'm taking guess that the piston screws into a metal liner in the aluminum caliper assembly and that might be rotating when I turn the piston.

Anyone had a similar experience?

[alexperkins]

You have to apply pressure to tighten it in as you go. The Laser brake caliper rewind tool is very good.

[littlepolo]

It was a Laser tool but the drive pins did not sit in the piston properly hence difficult to get leverage.

The pitch of the drive pins was too short on one side and too wide on the other.

However, I was able to apply a reasonable amount of pressure using a big screwdriver.

Are you familiar with the mechanism - how the piston is threaded?

[alexperkins]

The laser tool I have flips over (the silver disk) so it has two different sets of pins

You lock the plate into the caliper, then hold the silver lock ring tight with a spanner and tigthen that anti clockwise, whilst rotating the threaded section clockwise.

[littlepolo]

Thanks again. As I mentioned the Laser too pins did not align with the piston so I will need to try and find another tool.

Question is if its a thread why would it need pressure and rotation to move?

[alexperkins]

The rotation is only for the handbrake. The piston doesnt rotate under normal brake operation

http://www.halfords.com/workshop-tools/ ... ewind-tool

Thats the tool I use and it works perfectly on the small pin side.

[littlepolo]

That is the exact same tool I used - it was useless.

The piston I have has a kind of cross pattern with four lugs, was yours the same (some have only two)?

Just for clarification - so the piston does not need to turn to retract (rotation is only for handbrake)?

In that case what I need is a clamp to put pressure on the piston for it to retract?

[alexperkins]

Yeah - i managed to get it to lock on ok though

No, you need to rotate it and apply pressure to make it wind in. My point was more that when the piston comes out under brake operation it doesnt rotate. Thats just for the handbrake.

The black plate should sit where the pads are, and lock into the silver nut then you can tigthen that up against the plate, and then rotate the inside spindle if that makes sense so rotate it, but apply pressure at the same time. Youll need to keep tightening the silver nut as you go.

[RUM4MO]

littlepolo, it was not you that reported having non-standard rear calliper pistons some time ago was it?

If not then you are not the first person to report, on a VAG forum to have that type of piston, which from my experience of owning new VW cars from 2000>2015 is not what was fitted at the factory.

So, your car seems to have either had aftermarket pistons fitted to these callipers, or someone replaced the callipers with some aftermarket ones, probably to save money?

In reality, you would need to buy a universal kit of bits to rewind these pistons, or get a garage with a universal kit to rewind them - not good!

Edit:- by the way, the correct rear calliper pistons should have a couple of blind holes (loose description) for the pins in that or any other compatible rewind tool to locate into.

Next Edit:- right, I've had a look back and see it was not you that reported having this "X" pattern or "4 segments" on the surface of the rear calliper piston (it was you and I that were posting on the airbox/pinking issue!!) I traded that car in last August for a new 1.2TSI SEL for my wife!(while still feeding it on UL+ even after replacing the oil separator)

[RUM4MO]

littlepolo, maybe stuff " VW POLO 2003 REAR BRAKE CALLIPERS FOR SALE" into Google and you should get at least one picture of a new calliper that shows what the correct/normal piston face should look like. I was presented with a LUCAS aftermarket one - which is fair enough as real Lucas used to manufacture these items having bought over Girling, but eventually Lucas stopped making them and handed that job over to TWR (I think) who still manufacture these items for new VAG cars.

[littlepolo]

Hello there. The caliper assembly fitted is definitely a Lucas part because I noted that whilst doing the work. There is an X pattern and the pitch of the Laser tool 22mm is just too short to sit into the piston lugs. Looking at parts for sale it seems the pistons all have two lugs and I can see the Laser tool would work well with them.

[RUM4MO]

Just one thing, I've forgotten if you said this in earlier threads, have you owned this car from new, and if so, did you ever get a garage to replace either of these callipers.

Lucas - I could be wrong here, but I'd not expect to see Lucas mentioned any where on these callipers as Lucas as a brake manufacturer had shut up shop before that car was built - or had they? (official time for TRW to buy up Lucas was 1999, I think that that was just the brake parts division, some other parts went elsewhere and eventually someone bought the remainder cheaply and rented out the name for covering cheap nasty stuff - ie as below!)

Latterly, I think that the Lucas name was been rented out by the final owner of that company name (maybe someone in ECP?) - which should explain why you would be well advised to avoid buying any Lucas branded car bulbs - as they are cheap tat and do not represent what the original Lucas company made!

The motor trade will still refer to these callipers as "Lucas" but that is just a legacy thing which we all do in respect to some prominent manufacturers parts.

Seeing that Lucas branded calliper for sale when I checked Google before replying to you yesterday did not surprise me - again, if new and genuine it should have be branded TRW - though it did show the correct pattern on the piston!

[littlepolo]

I have not had the car from new but have a near-complete service history. I'll check through the papers.