Bora rear brake cailper

[DIYspanner]

Bora 1.9 TDi Sept '99

Whats the best way to get the piston pushed back to put new pads in?

Its a combined footbrake/handbrake caliper.

 

[Burnerman]

It has to be turned clockwise as its pushed in, mate - there are rewind tools to do this but you may get away by turning the piston with water pump pliers as you gently push the piston back with a small 'g' cramp. Don't rupture the rubber seal!
Some go back easily (Hondas) and some dont......
John

 

[gregers]

dunno wether john would agree,but on the sharans tdi versions it is argued that you release the bleed nipple or you may flip the seal on the abs pump?

 

[Burnerman]

Certainly I can't comment factually on this one, but there are loads of VAG cars with this set up, I've replaced loads of pads and discs and never had an issue (apart from leaking alloy washers on the banjo bolts which were always occurring).
The fact that the piston is pushed back very slowly should keep things wholesome - I remember the same claim was made regarding the master cylinders on Vauxhalls which turned out to be whitewash but I'll certainly ask around!
Pushing the fluid out through the open bleed nipple can't do any harm, especially as the brake fluid is meant to be replaced at intervals anyway.
John

 

[gregers]

unlike yourself john i am far from an expert but on a couple of car forums i help run the tech guys have banded this on many occassions.

 

[Burnerman]

I'll certainly make enquiries and thanks mate..
Makes you think that only a main dealer will be able to access the bonnet catch in the future
John

 

[DIYspanner]

I'm in the middle of changing rear the pads and discs of a Bora diesel.

I got universal caliper tool when I bought the pads. The tool is basically a metal cube with spikes on it but I had to power file a the spikes on one side to get it to fit into the caliper piston keys ways.

With the bleed nipple open it took a hell of a lot of turning to get the piston screwed back.

 

[Burnerman]

I use a Laser wind back tool....the reversible anvil fits most makes, I find.
The trick is - and its easier said than done - is to keep everything square so you aren't trying to bend the calliper instead of rotating the pistons.
John

 

[DIYspanner]

Thanks Burnerman

What I did was dismantle the caliper and reassemble with out the pads so it was secured to the hub and easy to push and turn at the same time - the piston must be on a very fine thread I'm guessing?

 

[Mursal]

On a very practical level, the chances of turning the seals in the ABS unit is slim.
But the chances of letting air into the system by loosening the bleeder when flapping about with the caliper/piston is extremely high.
Then you have a problem and have to start bleeding to get the brake pedal back up to a solid normal feel.

I'd leave the bleeder tight and go back in steady, but that's just me

 

[Burnerman]

Thanks Burnerman

What I did was dismantle the caliper and reassemble with out the pads so it was secured to the hub and easy to push and turn at the same time - the piston must be on a very fine thread I'm guessing?

The thread is quite fine, and its in the centre of the piston itself.
With my wind back tool, its possible to do things your way, but only with the disc off.....I get by with holding the calliper in one hand and operating the rewinder with the other.
John

 

[DIYspanner]

Mursal,
I appreciate what you say about air getting in via an opened bleed nipple but I always push caliper pistons back with the bleed nipple open.

I used to push the fluid back up into the master cylinder until an experience with a Vauxhall Astra when pushing the fluid back up into the master flipped the seals and I had to get a new master.

Since then I always push the caliper piston back with nipple open. Two or three pushes on the brake pedal gets any air out.

By the way, I've replaced the discs and pads with Comline brand and I'm impressed with the quality - until now have always been a Mintex user.