Rear Brake Caliper Piston Seals

[Tim1111]

Did the rear bearings, pads and discs on the gti recently but managed to tear one of the seals and the other side was very deteriorated. Got the seals on order to pick up this week, but thought I'd check if there are any pointers on here to fit them. I'm assuming they just slip over the piston to act as dust covers, but what's the best way to get the piston out to remove old and fit new? Or are they attached to the caliper at the bottom rather than the piston?

Do the pistons need to be spun out (like putting in with special tool but no pressure and turning the other way obviously), or can I just remove the caliper and press the brake (although I'm sure I've been told never to do this in the dim and distant past)?

Any help greatly appreciated to try and get this job done quickly.

[rubjonny]

you'll need a proper tool:
http://www.justoffbase.co.uk/Disc-Brake-Piston-Wind-Back-Tool-with-Double-Adaptor-Sealey-VS024?category=113

the piston needs winding right out before the boot can be replaced, there is also an internal seal which will be included with the kit if you bought it from VW. also the kit includes a sachet of grease, the seals need soaking in this for around 40minutes before you fit them

[Tim1111]

I've got the tool, just wasn't sure how to get the piston out. I assume it will just wind out then, opposite of winding it in. I'm sure it will be a bit more obvious once I've got the seals to look at and the pistons wound out.

Thanks for the reply.

[rubjonny]

yep just unscrew it with the tool, you can work them out with the handbrake lever too, but that can be a bit of a chore

[Tim1111]

Cheers mate. Just picked up the seals so I'll get the old ones off and I should be able to work out how it all sits in with the internal seals.

[Tim1111]

I've had a look in the Haynes manual and it talks about the piston (fluid) seal and removing the piston to put the new dust seal on which has raised a few questions.

Are the following assumptions right before I start:
1) The internal seals that came in the kit are the piston (fluid) seals that I won't need as I just want to replace the dust seals?
2) I don't need to take the caliper off the brake line and dismantle to replace the dust seals, I just wind out the piston far enough to get the old one off and new one on ?
3) Haynes says if you wind the piston out far enough it will just come out by hand. If I'm doing this without removing the caliper from the brake line is there a danger I'll wind it out too far and it'll come out causing a right mess?

Thanks for your help.

[rubjonny]

you cant really replace the dust seal without having the piston out completly, the problem is the dust seal lip is inside where the piston sits if you get me?  when I do it I put the dust seal on the back end of the piston loose, then hook the lip in all the way round. once you do that then push/wind the piston in untill you can slide the boot up into the slot on the seal.

Its hard to explain but you'll get what I mean when you look at it.

[Tim1111]

So it's a case of removing the caliper then? I  was hoping it was just a case of wind out the piston with caliper still attached, replace dust seal and wind back in again.

To be honest, reading through Haynes it doesn't sound that major a job - just not the quick job I was hoping for.

Thanks for the advice rubjonny, I think I understand what you mean and I'm sure it'll all become obvious when it's apart in front of me.