Caipler (spell?) rebuild question
Discussion
Hiya I really like that spinning smiley, look cool. anyway. Im about to do my first caliper rebuild before putting them on my car.
its AP racing 4 pot vented calipers, and i accquired them from scrapyard after i looked around for best condition.
How do i remove those piston and seal without special tools?
and when putting things back, do i oil my piston in clean brake fluid?
and how do u know caliper is scrap or not? Pitting, and other else ? i cant remember what.
THANKS
Jay
its AP racing 4 pot vented calipers, and i accquired them from scrapyard after i looked around for best condition.
How do i remove those piston and seal without special tools?
and when putting things back, do i oil my piston in clean brake fluid?
and how do u know caliper is scrap or not? Pitting, and other else ? i cant remember what.
THANKS
Jay
I used to be nervous about splitting the caliper, but thought I would try it anyway. I have only done the Cooper 'S' twin pot type, but I don't see why a 4-pot should be any different.
Ideally use a new seal or seals to go between the two halves when you come to re-assemble.
After splitting into the two halves you remove the old pistons. Remember, in a disc brake caliper, unlike a wheel cylinder, the main piston seals sit in the caliper, not on the piston. That's why it's easy. If any are stuck you can apply either hydraulic or air pressure to free them.
With it all in pieces, including removal of the bleed nipple, you clean everything extremely well. Check the threads for the bleed nipple, I once found them partially stripped. If they are you can 'helicoil' them as a perfectly satisfactory repair.
I normally clean all the bits with meths, then finally clean the piston bores with brake fluid - it's a bit of a messy job!
To re-assemble, first fit the new seals into the caliper halves. Use some brake seal rubber grease around the seal edges prior to fitting the new pistons, and go for the stainless steel ones. Make sure the seals do not get diplaced from their seats when you insert the pistons.
Once the pistons are installed and pushed firmly but gently to the limit of the caliper bore, fit the (new) seals that go between the two caliper halves, using a bit of rubber grease to help here, (but just a tiny bit).
Re-join the two halves using 'loctite' on the bolt threads, but don't over-tighten. I don't know what the correct torque is, but just use your best judgement.
Refit to the hubs and fit the (new?) brake hoses. I always use the Aeroquip type. Fit some pads and bleed out. Then remove the pads and test that all pistons are operating correctly by pressing the brake pedal GENTLY down. Whatever you do don't push the pistons too far out. You can put some worn out pads in during this test to prevent over-travel of the pistons.
If all OK (it will be!) finally re-fit the new pads and Bob's your Uncle.
The motto for all brake strip downs is "Cleanliness, cleanliness, cleanliness".
I hope this helps. Email me personally if you have any queries.
Peter
Ideally use a new seal or seals to go between the two halves when you come to re-assemble.
After splitting into the two halves you remove the old pistons. Remember, in a disc brake caliper, unlike a wheel cylinder, the main piston seals sit in the caliper, not on the piston. That's why it's easy. If any are stuck you can apply either hydraulic or air pressure to free them.
With it all in pieces, including removal of the bleed nipple, you clean everything extremely well. Check the threads for the bleed nipple, I once found them partially stripped. If they are you can 'helicoil' them as a perfectly satisfactory repair.
I normally clean all the bits with meths, then finally clean the piston bores with brake fluid - it's a bit of a messy job!
To re-assemble, first fit the new seals into the caliper halves. Use some brake seal rubber grease around the seal edges prior to fitting the new pistons, and go for the stainless steel ones. Make sure the seals do not get diplaced from their seats when you insert the pistons.
Once the pistons are installed and pushed firmly but gently to the limit of the caliper bore, fit the (new) seals that go between the two caliper halves, using a bit of rubber grease to help here, (but just a tiny bit).
Re-join the two halves using 'loctite' on the bolt threads, but don't over-tighten. I don't know what the correct torque is, but just use your best judgement.
Refit to the hubs and fit the (new?) brake hoses. I always use the Aeroquip type. Fit some pads and bleed out. Then remove the pads and test that all pistons are operating correctly by pressing the brake pedal GENTLY down. Whatever you do don't push the pistons too far out. You can put some worn out pads in during this test to prevent over-travel of the pistons.
If all OK (it will be!) finally re-fit the new pads and Bob's your Uncle.
The motto for all brake strip downs is "Cleanliness, cleanliness, cleanliness".
I hope this helps. Email me personally if you have any queries.
Peter
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