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How to get pistons out of rear caliper?

  • Thread starter Thread starter shortlid
  • Start date Start date
S

shortlid

Guest
OK, I have the seals to re-build my draging rear caliper. How do I force the pistons out to hone an dput new seals in them?? :?: Compressed air, grease gun?
 
Air pressure is the trick buddy. I used a bicycle pump, and fabricated a fitting for the bleed screw. Make sure your fingers aren't in there, and use a rag or something to prevent the piston getting dinged when it fires out like a gunshot...
 
Compressor OK?

Compressor OK?

Here ar work we have a rubber tipped blow off tool hooked to a 120 psi compressor will that work, or too powerfull? :twisted:
 
Re: Compressor OK?

Re: Compressor OK?

shortlid said:
Here ar work we have a rubber tipped blow off tool hooked to a 120 psi compressor will that work, or too powerfull? :twisted:
Click to expand...

That's what I used but I had the pressure dialed back to about 30 - 40 PSI. 120 may be a bit much I would think.
 
When I did it, I pumped the handle on the bike pump once, the gauge on the pump showed about 50lbs, and in about 30 seconds the piston shot out like a bullet. I was surprised it didn't crack the cast housing of the brake caliper or damage the piston, but it did dent the housing. Make sure your hand isn't in there...
 
Definitely dial it back to start. If it doesn't come out then I would slowly up the pressure. In addition to making sure there is something soft for it to hit when it comes out (it really blasts out of there even with lower pressure), look out for brake fluid spraying out all over the place.

I had a piston that wouldn't come out even with a full 125 PSI from my compressor. I finally got it out by putting the caliper in a vice (padded jaws) and using two screwdrivers prying up under the lip on the piston from both sides - I put popsicle sticks under the screwdrivers to keep from damaging the caliper housing. Then thicker wood shims as it got further out. It was a bear, but I finally got it.

It's also easier if you don't split the caliper halfs - that just make one more hole for the air to leak out.

Good luck
 
Can't get it out!!

Can't get it out!!

OK I can't ap[ply anough pressure with out leaking with the blow off tool.!! :evil: Will a hose attached some where work?
 
On really sticky ones, I have reconnected the lines and used the brake pedal.
 
Pull the wheel.

Remove the pads.

PLace small piece of wood between piston and caliper.

Step on rear brake pedal.

Mop up brake fluid.
 
Shortlid, Lots of useful suggestions here, all of which work in some fashion or other. I prefer to wrap the entire caliper completely in a grease rag, leaving the brake fluid line port where you can reach it with a rubber-tipped air nozzle. My nozzle has a fairly long lever so I can begin with low pressure and slowly increase it until it pops the piston out. You ARE going to spray fluid out, but the rag will keep that from painting your shop space, and the rag will more or less prevent the piston from bopping the spouse in the head in the event that you're doing this in your living room while watching football... After you've separated the piston out and performed your hone/polish, do yourself a favor and open the bleeder nipple when you begin to rinse out the caliper with whatever solvent you prefer to use.
 
Re-connected an only ONE came out??

Re-connected an only ONE came out??

Ok, used the hydro. system (rear brake master cyl. to push the piston out. I even put the wood wedge in there. But it only poped one piston out the other moved a bit but would not make it the rest of the way!! :evil:

Any other ideas guys?
 
Yep, when one comes out and the other doesn't, it gets tougher since you can't pressurize the system. See my previous post with instructions on prying it out. If you go slowly, pad things, and work evenly from both sides, you can do it without damaging anything... It might be easier if you split the caliper - you can get better access to it that way.

Good luck
 
If you remove and drain it life will be easier on you. Simply plug the joining hole shut with a plug and finger and then pressurize with a blow nossle with rubber tip like described above. It WILL pop out of there. Follow the precautions mentioned, be careful.
 
Re: Re-connected an only ONE came out??

Re: Re-connected an only ONE came out??

shortlid said:
Ok, used the hydro. system (rear brake master cyl. to push the piston out. I even put the wood wedge in there. But it only poped one piston out the other moved a bit but would not make it the rest of the way!! :evil:

Any other ideas guys?
Click to expand...

If you reinsert the one that came out, then use a C-clamp to keep it from coming all the way out, then the pressure will be applied to the stubborn one.
 
What ever you do-- DO NOT USE CHANNEL-LOCKS!!!

Previous owner of my Honda destroyed piston this way. Took me 2 months to get another to the tune of $85.00. Do not reach for channel locks, maybe a strap-wrench, but no channel locks!
 
Hoomgar said:
If you remove and drain it life will be easier on you. Simply plug the joining hole shut with a plug and finger and then pressurize with a blow nossle with rubber tip like described above. It WILL pop out of there. Follow the precautions mentioned, be careful.
Click to expand...

Don't do this.

If you place a finger near a hole and pressurize the fluid behind it the fluid can be injected into your skin. If you have to work with air under these circumstances use no more than 30 psi. One small slip could be very bad.

vaccine injection devices use air pressure to administer with, brake fluid can be harmful if injested.
 
I personally would be very hesitant to touch the pistons with anything made of metal. Screwdriver tips, pliers, channel-locks, anything. Unless I miss my guess, those pistons are made of aluminum. The instant that you apply pressure of any sort to that polished, machined surface, you're going to mar it. Scratch it. Scar it. Damage it. Then you have a piston that no longer fits smoothly into the cylinder bore... draggy, sticking brakes if they function at all. Partially push the first piston back in place, enough to seal the o-ring a bit and hold that one in place while you re-pressurize the caliper with air, hydraulic fluid... whatever. That will force the pressure back onto the sticky piston. Basically what you want to happen is to first remove the farthest piston from where the fluid or air pressure comes in to the caliper. Once you've gotten that farthest one, the closer one will still usually pop out with moderate pressure. Even with the pressure leaking through the orifice, the first piston should pop out.
 
An elegant solution. That just HALTS me in my tracks. Ya'll just BRAKE me up. BIND me up and wrap me in a red bow. Somebody STOP me! (I have entirely too much fun here :) )
 
Piston removal

Piston removal

This may be too simple, but whenever I work on my seals I just pump the pistions out to their furthest travel using extra brake fluid. If I am lucky one usually becomes unseated and pops out. The other one I pull out with a reverse pair of pliers, pliers that push out rather than clamp onto. In my case, 81 GS1100EX, I have to split the rear caliper to get the second piston out. Good Luck
 
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