Itinerant Air-Cooled

Having trouble getting the pistons out of a 78 brake caliper.

Figger I will have to use the hydraulics to push at least one of them out. (I will do the outer one so I can keep the inner one hooked up for possible port blockage and more hydraulic pressure.

Oooh just had a flash, I could bl.ock the ports that feed the outer caliper with somethin and reassemble to push the inner piston out as well....Hmmmmm

Anyway, if you have tips on how to do this let me know.

The cylinders have a nice little rusty ring on the disc side of the piston seal. they push in but I can't get them to move the other way. Air pressure isn't working. They are soaking in penetrant as we speak.

Got me on that one --- I never knew they could be removed. What do you need it out for - just curious.

Colin told me to take the caliper off of the rotor, and then put a piece of plywood in the center, hit the brakes. Remove.

chitwnvw wrote:Colin told me to take the caliper off of the rotor, and then put a piece of plywood in the center, hit the brakes. Remove.

That's a nice trick, but I have an extra pair of calipers that I would like to repair. I remember years ago. We used to shoot air into the hydraulic passage ways with motorcycle calipers.

The air pressure will usually work but you gotta watch out for flying pistons. Use a rag in your hand to hold over it. That baby will fly outta there.

These calipers have a nice little ring of rust that has formed on the cylinder under the dust cap. That's what was holding them so the brakes were siezed.

The hydraulic pressure is really the way to go. The trick being that once you have one side out there is no resistance for the other side. My plan is to hold the inner side in place and push the outer piston out. Once out I will dissassemble the caliper and block the ports that feed the outside with a wad of rubber or something; reassemble and then push the inner piston out.

Lazy sumbich that I am I was hoping for the 'magic trick'.

I am trying to get this beast together with the least amount of $$$ as possible as little bro has none and I have my own parts to buy.

The first caliper is working great after clean and reassemble.

The real trick was getting the piston sealing ring out without using a pick so as to not damage it's sealability. I used a controlled air flow to blow it out of it's track.

Update.

Got em apart and cleaned up. They work great.

Had to do some down home mechanican cause my hydraulic plan only worked for trhe first piston. the second piston would not push out cause I couldn't get a tight enough seal to hold back the fluid to push it out.

I got the piston most of the way out and grabbed ahold of it in a vice near the top end, at the point above the seal. I knew I would put some dings in the piston by grabbing it but they were in a place where they would not scratch up the rubber seal in the cylinder. Then I took a drift and began tapping the caliper around the circumference of the piston. little by little it moved and then let go. Much more rust on this side. cleaned up the rust and gave a light hone. cleaned and reassembled.

Now on to the next system. Shift Linkage.

Nice work.

So tell me more how you were able to get it out on the bench with hydraulic fluid. Did you put some in a tube and blow some air behind it?

Tried to do it with air on the bench and splattered brake fluid all over.

I re-attached it to the connection on the vehicle. Held the inner piston in place with baling wire and pushed out the outer piston with the brake pedal.

I loosened the caliper halves and slipped in some plastic (pieces of a paint spraycan lid). When I clamped it back together the fluid just squirted around without moving the piston. If I were to try it again I think I would use plastic from a butter/cottage cheese container as it is more malleable. By the time I was deciding it was time to put it in the vehicle it was 10pm and I was done wrestling with the caliper while it was hanging from the brake line.

Gypsie wrote: The hydraulic pressure is really the way to go. The trick being that once you have one side out there is no resistance for the other side. My plan is to hold the inner side in place and push the outer piston out.

Yeah, what I said was to put a block of wood or even a good non-worn brake pad between the disk and the caliper piston on the side you don't want to remove (making sure that the other caliper is assembled or blocked as well), then hammer that brake pedal down with the engine running if your booster is good.
Colin

Couldn't you just remove the brake pad on the side you want to remove the piston from?

I found that even with the pads removed there was not enough clearance for the pisonts to come out of the caliper. They just squeezed the disc at full out. I then had to open the bleeders to push the pistons back far enough to clear the little lip around the disc perimeter and remove the caliper.

The free hanging caliper (supported with wire, not hanging by the brake line!) had enough clearance to allow the piston to be pushed out while the inner piston was held in place with more baling wire.

After the first one (outer piston) came out the ports were open and therefore did not provide any resistance for the fluid to push out the inner piston. Blocking the ports would have worked if I had pliable enough material to be squeezed between the inner and outer caliper. The spray can lid was just too rigid to make a good seal.

Good Idea to have the engine running. I did it dead and it still worked pretty well.

OK after doing my brothers brake system I was noticing more how unresponsive my brakes were being. Stopping when I want to is pretty important to me so I went out and got the works for my rig (rotors, pads, drums, shoes and front bearings.

Hydraulics seem to be ok, though I will be squirting out the old fluid with some new dot 4.

Bentley suggests a lubricant called brake paste for some of the innards. Any suggestion about alternative lube for these workings. I know what my fave would be (nudge nudge, wink wink...)

I found that my rear shoes had worn in a pattern around the top side about 4 inches the rest of the shoe didn't look like it had been worn. I did find that the self dajust star on the right side was not turning because the PO had installed the return springs upside down and it was not allowing the brake to be adjusted. But the other side had a similar wear pattern and the star was doing it's thing. Is there some trick to mounting that puts the shoes in the proper place?

I think Bob stood a little too close and he caught what I have as I hear he went out and got some brake parts too....
I need to learn to cover my parts when I wrench....

Gypsie wrote:Bentley suggests a lubricant called brake paste for some of the innards.

I found that my rear shoes had worn in a pattern around the top side about 4 inches

That paste was pretty good stuff. Don't know where to get it.

Shoe wear like that is usually due to inadequate adjustment at the anchor for those of us who need to manually adjust brakes, but self-adjusters can do that as well if they are slightly sticky as well as totally inoperable.
Colin

One trick I have used with success is to make up a short brake line with appropriate fittings so that you can pump grease into the caliper with a grease gun. This exerts amazing force, and that piston will come out. You do have lots of grease to deal with afterwards but at least it's non-destructive.
In a more severe case, with calipers that split into two halves, I drilled a hole right through the centre of the piston, tapped said hole, and then turned a bolt into it, which drew out the (destroyed) piston. Saved the caliper anyway.
Jim

eggselent suggestions. I love figgerin' things out...