What you need :
- One seal kit per caliper. Each kit consists of 4 main fluid seals, 4 wiper seals and 4 wiper seal retaining rings (sometimes called dust rings)
- New pistons
- Brake Caliper Lube / Rubber Grease
This is a cross-section of the three parts included in a kit. Note the "V" groove in the wiper seal as opposed to the square cross-section of the main seal.
Disclaimer : It is quite easy to install the seal kit in the calipers, but if you're not confident enough, take it to a professional brake shop. it is YOUR responsbility to ensure that the work is done properly. I was quoted around $100 to do it.
I have previously removed the pistons - see post on 12 Dec 09 http://mearcatmini.blogspot.com/2009/12/painting-on-metro-brakes.html. Most of the old pistons were badly pitted and so were thrown out. Re-installing pistons such as these is a BAD idea as it will ruin the seals in no time and will start leaking. The left piston had some marks on the surface, the middle piston had the hard chrome lifting from the surface. The right piston is the new stainless steel one which will never have the issue of the brake fluid getting under the hard chrome surface.
With a screwdriver, lever out the wiper seal and ring
Do the same for the main seal
If the bores are dirty of have deposits of old brake fluid & genera crud in them, get some 600grit sandpaper and wet sand the bores until clean.
Loosen or remove the bleed screws in the calipers. If you don't, then you find it very hard to push the pistons in later as there is nowhere for the air in the calipers to escape. Clean out the bores with some brake fluid or methylated spirits and dry off with a lint free rag to remove.
Coat a new fluid seal with brake lube (seal must be dry before applying) and ease the seal into the groove in the piston bore. The seal will sit slightly proud of the bore. Provide a liberal coating of brake lube on a piston and insert the piston into the bore until about 8-10mm of the piston is still protruding. The piston MUST be square and not tilted when inserting it.
Coat a wiper seal (has the "V" groove inside the seal) in brake lube (seal must be dry) and fit into a metal retainer. This can be tricky to do when you hands are covered in grease :) Slide the seal and ring (seal facing inward) over the piston and push up against the bore mouth.
The retaining ring is a press fit into the top of the piston bore. I found it useful to push (ny hand) the outside part of the ring into the bore mouth first and then use a G-clamp to clamp the piston and press the retaining ring in place. You may find you will here a small click when the retaining ring seats into place. Do NOT be tempted to get anything like a punch to try and force the ring into place - they damage easily. If the ring does not seat properly, use a G-Clamp (and some bits of wood) on the parts of the ring that are sitting too high.
Once complete, repeat 7 times :)
- One seal kit per caliper. Each kit consists of 4 main fluid seals, 4 wiper seals and 4 wiper seal retaining rings (sometimes called dust rings)
- New pistons
- Brake Caliper Lube / Rubber Grease
This is a cross-section of the three parts included in a kit. Note the "V" groove in the wiper seal as opposed to the square cross-section of the main seal.
Disclaimer : It is quite easy to install the seal kit in the calipers, but if you're not confident enough, take it to a professional brake shop. it is YOUR responsbility to ensure that the work is done properly. I was quoted around $100 to do it.
I have previously removed the pistons - see post on 12 Dec 09 http://mearcatmini.blogspot.com/2009/12/painting-on-metro-brakes.html. Most of the old pistons were badly pitted and so were thrown out. Re-installing pistons such as these is a BAD idea as it will ruin the seals in no time and will start leaking. The left piston had some marks on the surface, the middle piston had the hard chrome lifting from the surface. The right piston is the new stainless steel one which will never have the issue of the brake fluid getting under the hard chrome surface.
With a screwdriver, lever out the wiper seal and ring
Do the same for the main seal
If the bores are dirty of have deposits of old brake fluid & genera crud in them, get some 600grit sandpaper and wet sand the bores until clean.
Loosen or remove the bleed screws in the calipers. If you don't, then you find it very hard to push the pistons in later as there is nowhere for the air in the calipers to escape. Clean out the bores with some brake fluid or methylated spirits and dry off with a lint free rag to remove.
Coat a new fluid seal with brake lube (seal must be dry before applying) and ease the seal into the groove in the piston bore. The seal will sit slightly proud of the bore. Provide a liberal coating of brake lube on a piston and insert the piston into the bore until about 8-10mm of the piston is still protruding. The piston MUST be square and not tilted when inserting it.
Coat a wiper seal (has the "V" groove inside the seal) in brake lube (seal must be dry) and fit into a metal retainer. This can be tricky to do when you hands are covered in grease :) Slide the seal and ring (seal facing inward) over the piston and push up against the bore mouth.
The retaining ring is a press fit into the top of the piston bore. I found it useful to push (ny hand) the outside part of the ring into the bore mouth first and then use a G-clamp to clamp the piston and press the retaining ring in place. You may find you will here a small click when the retaining ring seats into place. Do NOT be tempted to get anything like a punch to try and force the ring into place - they damage easily. If the ring does not seat properly, use a G-Clamp (and some bits of wood) on the parts of the ring that are sitting too high.
Once complete, repeat 7 times :)
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