Caliper piston removal options

[mtull]

My goal is to get the brakes working well enough to safely move my project car onto a trailer for safe transport.  The car hasn't moved under it's own power since the late 1970s. The caliper (KH 80012) pistons are stuck in the bores.  I tried compressed air but had no luck, I think the problem was lack of airtight seal around the end of the air chuck or perhaps the fool holding the air chuck (me).  Anyway I'm not comfortable using air pressure anyway and would like to explore more options before giving up and sending them out for rebuild. 

I believe the original service manuals suggested using Miller C4087 however the only complete C4087 I've come across for sale is $130.  A few forum posts suggest using grease gun via the appropriate fittings, does anyone have a list of the fittings needed for this approach?

I'm not apposed to sending the calipers out for rebuild but was hoping to defer until I'm ready to restore the entire car.

Any suggestions appreciated.
Thank you.

[Bullitt-]

  I would try using the car's master cylinder with if it can still build pressure. 

[mtull]

I would try using the car's master cylinder with if it can still build pressure.

I don't think that will be an option at the moment as the master cylinder seems to be stuck as well.  I removed the master cylinder from the brake booster which then allowed the brake pedal to travel to the floor and back.  I do have the correct 70 only brake pedal linkage thus, I'm not sure if the master cylinder is really stuck or if it's another problem.  With that said I thought about buying a cheap master cylinder and trying your approach.  Thank you for the suggestion.

[1970 cuda Joe]

Take the caliper off & fill it with Evap-o-rust for a couple of days. Drain it (if you don't want to get wet). Put a block of wood where the pads go & use a rubber tip blow gun to push the piston out. Usually loud when it coms out. Don't forget the leave the bleader screw in...Joe

[mtull]

use a rubber tip blow gun

I hadn't thought of that,  I'll give the rubber tip a try this weekend.

Thank you!

[MoparLeo]

If the piston is not bottomed out, use a C-clamp with an old brake pad in place and justslowly compress the piston ineo the caliper. Then you can put a piece of 2x4 into the caliper where the pads and rotor would normally be and use the compressed air to push the piston back out. This is how we did it in the shop when doing caliper rebuilds.. Keeps your fingers clear of the piston !!!
 Check my next post for videos.

[JH27N0B]

If you can force it back with a clamp like Leo described, that would be optimal.
I talked to a brake rebuilder years ago about getting frozen pistons out of master cylinders when compressed air wasn't working. He said they used grease.  Pump grease into the cylinder and it forces pistons out regardless of how rusted in place they are!

[mtull]

If the piston is not bottomed out, use a C-clamp with an old brake pad in place and just slowly compress the piston into the caliper. Then you can put a piece of 2x4 into the caliper where the p[ads and rotor would normally be and use the compressed air to push the piston back out. This is how we did it in the shop when doing caliper rebuilds.. Keeps your fingers clear of the piston !!!

Thank you for the suggestion, I'll take a closer look tomorrow.  It would be so nice if the C-clamp approach helps it move at least in one direction.  I'll pay especially close attention to: "Keeps your fingers clear of the piston !!!"

A few months back I soaked both calipers in Evapo-Rust but I don't believe I tried to push the piston in.  I'll let you know how it goes.

[MoparLeo]

https://www.youtube.com/watch?v=yBbazU2Spvk
https://www.youtube.com/watch?v=2L7fcgXhksI

[mtull]

https://www.youtube.com/watch?v=2L7fcgXhksI

Great Video.  Thank you

[Mr Cuda]

 I really like the grease gun idea/trick.
I will keep that in mind if I ever get a stuck caliper. No danger of sudden exit.
 I always popped the pistons out of stored calipers as they came off the parts car.

[mtull]

I tried a rubber tipped air chuck but couldn't create a tight enough seal to build sufficient pressure to get any piston movement.  I then tried a clamp to compress the piston into the bore.  No movement however it's possible the piston is already bottomed out?  I attached pics but understand it may be impossible to tell if the piston is bottomed out or not from just a picture.  Any thoughts appreciated. 

I think I'll try the brake-hose-to-air-compressor hose idea used in the video suggested by @MoparLeo.

Also found some other interested details, see pics.  You can see it's heavily pitted and was very rusty prior to a few days in Evapo-Rust.  Depending on the angle of the light I can barely make out a '9' where the assembly date is typically found but have no idea if '9' in this case represents the year or one of the three digit days of the year.  I think the casting date is 192, which might be July 11, 1969.

Thank you all for your suggestions, I really appreciate the time everyone takes to assist others on our forum.
M.