1979 front brake caliper.

[Anthony10370]

Hello again,

Well I am trying to rebuild my brake calipers (one at a time) to do a complete brake job, and I cannot seem to remove the piston from the bore all the way. This is the first one (from a 928) I am rebuilding and it has not started well.

To remove the piston I have attached the disassembled brake caliper to the brake line and pressed the brake pedal a bunch of times, keeping an eye on the fluid level. However this has only popped it out what seems to be 99 percent of the way. I cannot pull the piston out, not even with a vice holding the front edge (non piston surface), and no matter how fast I stomp on the brake pedal, nothing happens except some brake fluid building up in the bucket (below the caliper).

This is where I am at:


Is there any way other than compressed air to remove the piston?, as I would rather not have a metal cylinder flying across the room at 900 MPH.


Thanks,
Anthony.

[Opelotus]

Is the piston cocked in its bore, preventing it from moving any farther? Can you push the piston back into the bore to verify this? Another possibility is that the lip seal on the piston is preventing it from being removed all the way. I have had similar problems with brake calipers slides getting stuck, ended up heating with a torch to get the slide to pop out, the damn plastic/rubber bushing swelled or something, making it stick. Not sure what to do in this case, as the assembly has brake fluid in it. Possibly try rotating the piston as you pull it out, use a pair of channel-lock pliers around the top edge of the piston.

[JK McDonald]

Hey Anthony10370, Get a Big Ass hammer and chisel - no wait that was my last project. I think using an air nozzle with a soft rubber nosecone and an air compressor is your best option to pop out the caliper piston. You also might try placing a “C Clamp” around the assembly to ease the piston back in and then as a back stop so the piston isn’t damaged as it comes out. Spray lots of WD40 down around the inner seals and usually a couple of brief shots of 40 - 50 psi of air pressure will do the job. Keep your fingers tucked well back…..

Once you have cleaned up everything and installed the new seal kit - use brake fluid for lubrication and the C clamp to gently ease the piston back into place. Make sure to square up the piston by releasing the clamping pressure a couple of times as the piston slides in. Take your time with the insertion by repeatedly turning the clamp a quarter turn - then release until it is completely seated or bottomed out.

Good Luck, Michael

[Anthony10370]

Got it out finally. Well after using compressed air, getting it cocked, retracting it, repeat, repeat, repeat, repeat, repeat; then practically beating the piss out of it with a soft blow hammer to get it realigned one time. Then used compressed air again and the piston came fully out.

Thanks for the C-clamp suggestion JK McDonald it worked to stop the piston nicely.

[Fabio421]

I have a pair of good early calipers I will sell you cheaply if you need them.


Edit: Nevermind. I see you got it out. Congrats.