Rear Brake Caliper Operation

[starmist]

I'm posting this for a mate of mine. He's just bought an 84 s3 and his rear disc is blueing and the handbrake wouldn't hold a baby donkey. I reckon his piston's seized and the pedal pressure is enough to operate the brake, but it's not releasing from the disc properly, but you can't put enough pressure on with the handbrake to engage the piston.

Does this sound about right?

Also how does the caliper work? I understand there's an internal ratchet to take up the slack on the handbrake and the pistons have to be wound in. How does this work?

[superdave]

Sounds like your rear calipers are seized. Very common problem to cars where climatic weather corrodes. Also the calipers are aluminium against cast which casues electrolitic corrosion. Basically the castsurround squashes the aluminium cylinder until it's not a true circle. This is when it seizes the piston. You can get them reconned for about £85. Try PNM Engineering on 0151 630 6101.


Cheers,



Dave Walters

[cnh1990]

If you remove the pads you will find the piston has a slot. If you use a 1/4"rachet handle into this slot the piston can be rotated to retract the piston. You can try some caliper grease on the piston, extract and retract the piston a few times to see if this will loosen it up. Also there is an access plate on the door sill to the rear of the hand brake handle. You might have to slide the seat up to see it. That is where the hand brake adjustment is located, it will need to be adjusted as the brake pads wear down.

The blueing could be from a sticky hand brake also.

Calvin

[starmist]

Thanks for your advise guys. I'll pass it on.