Brake Cylinder Ejection

[piscator]

Rebuilding brakes is part of my '79 SC Targa refresh. I searched the forum, reviewed the shop manual, and then found an interesting pamphlet that came with the ATE brakes seals.
The pamphlet describes a blocking plate to clamp onto the vacant side of the caliper after the first cylinder pops out. The pamphlet includes a (rather small) mechanical drawing of the blocking plate, but I rummaged around and found or fabricated some heavy disks that accomplished the same thing.

The photos are pretty much self explanatory.

[piscator]

The next photos are of the rear calipers. I found a 59 - 60mm fender washer that fit perfectly. I cut a piece of rubber the same size to provide a seal. The fender washer, by itself, was too flexible under the clamp and allowed grease to pass. I brazed a second washer onto the first and that worked perfectly.

[30westrob]

I have always used compressed air and a block of wood. Many ways to skin a cat.
Rob

[Arne2]

Originally Posted by 30westrob

I have always used compressed air and a block of wood. Many ways to skin a cat.
Rob

^ +1

That was always how I did it when I did that for a living.

[911tracker85]

I did not read this carefully, but I also just use compressed air.

now if they are really stuck using a grease gun may create more pressure than air.

so far have not needed to go there.....

[gomezoneill]

I just buy new calipers.

['78 SC]

Robert,

Thanks for posting this. I really like what you ended up with. I'm going to scrounge some combination of disks/washers/seals to make something similar. I'm surprised I never saw those instructions before.

I rebuild calipers often, so I invested in a pad spreader (pricey, but worth it). I found that placing it between the pistons and snugging it up before putting pressure on the caliper keeps the pistons square in their bores and helps ease them out without binding.

[Superman]

Originally Posted by 911tracker85

now if they are really stuck using a grease gun may create more pressure than air.

so far have not needed to go there.....

I just did mine. I first pulled the pads (one at a time), put some paint stirring sticks between the piston and rotor and used the brake pedal to push the pistons out. In this way, I verified they were moving okay, and nearly out of their bores. Then I used a small c-clamp on one piston while removing the other with air. It worked pretty well. There is a tutorial here on PP which is useful. For example, it says once you have replaced the inner o-ring thingie you can install the front pistons all the way in and the rubber boot is still easy to install, but not with the rears. With the rears, don't press the piston ALL the way in.

Easy schmeezy.

I also, for a change, opened the right rear bleed valve and let all that brake fluid just run out. Repeat for the other calipers. This reduced the usual brake fluid mess. I plan to fill the new master cylinder reservoir, and again use gravity to fill the calipers. Patience is a virtue.

[ClickClickBoom]

Originally Posted by 911tracker85

I did not read this carefully, but I also just use compressed air.

now if they are really stuck using a grease gun may create more pressure than air.

so far have not needed to go there.....

Grease is incompressible, air on the other hand is a wonderful way to shoot stuff around.

[Walt Fricke]

You are saying with grease you don't get that shot from a cannon effect you co with air, especially if you misjudged something?

Bit more work on the cleanup side, no?

[samurai_k]

I recently rebuilt calipers and found the plastic Irwin quick grip wood clamps work great with compressed air.

The technique that worked best was.

1. Clamp all of the Pistons.
2. Remove both bleeders.
3. Get a rag and cover one of the bleeder openings ... To not make a mess next.
4. Spray compressed air in one of the bleeder openings to push any old brake fluid out
5. Loosen one of the clamps and spray compressed air in to push one of the Pistons.
6. Do the same for the rest of the Pistons until all of them are about equally sticking out of the caliper and then pull out the Pistons by hand.

Sometimes if you loosen the clamps too much the Piston may come flying out so get a rag and cover the caliper to catch any rouge Pistons!



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