How to remove stuck Brake Caliper Pistons?

Help,

I'm trying to remove the brake caliper pistons but they're stuck!

I have a '82 750 Seca, it's been in storage for the past 12 years and one of the brake seals was leaking. I figured I'd replace seals and dust rings so I removed both calipers and they are on my bench. I put a C-clamp on one piston and slowly pressed it in a bit, but it was extremely tight. I tried pressurizing the calipers with 115psi to see if I could move the piston (on both) out but neither budges!

What should I try next?

thanks in advance for any suggestions.

George

 

Temporarily reconnect the caliper(s) back onto the brake lines (but not with brake pads and not assembled to bike fame & rotor), bleed brakes to get air out, and use brake pressure to pop the pistons out one pump at a time. Works like a charm every time for me. A bit messy when the piston finally does pop out, so have a bucket ready to catch the spill.

 

What did you pressurize it with? Compressed air? Mine was stuck too, I just pulled the caliper off, removed the pads and squeezed the lever to have the brake fluid push it out. It worked perfectly, just put the caliper in a plastic bag so fluid doesn't run everywhere.

 

I used my air compressor at 115 PSI and an air gun with rubber tip. I snugged the tip into the threaded brake hole and blasted away. Nothing. Piston didn't move, air didn't escape.

I guess I'll try bolting back on the brake lines, bleeding and squeezing them out that way. I'll have to equalize the piston extension dimension on both so one doesn't pop out before the other!

Thanks for the suggestion.

George

 

A much safer way is to use your grease gun. replace the bleeder screw with one that will allow the grease gun to fit on. Still have to clean out the grease, but it's a whole lot safer than making air gun out of your brake. Wow, that would be a what, 400 caliper airgun? <G> The grease would not run all over the place liek the brake fluid, and would go slower and more controlled, too.

ymmv,

dave

 

+1 on the grease gun. I used this trick a bunch of times, even on automotive calipers.
and..... most grease gun tips will fit right on a standard bleeder screw. it's absolutely the safest and easiest way to do it.

 

When I did mine, I had to let my compressor get up to it's max (130 psi) before it would pop out. Even then it slowly creeped out.

 

shop air is has a relatively low pressure when compared to hydraulic brakes, and even more so, a grease gun, hence the steel line, or reinforced hoses. I'd recommend either of the 2 but not shop air. I have had great success putting the caliper in a vise and opening the bleeder too. Once it's moving, the rest is easy.

Good luck!

 

All, thanks for your help.

In the time since I posted last, I remounted the calipers, stuck a home-made vacuum pump on the bleeders, pumped out the air & filled the lines & reservoir with fresh fluid. Started cranking on the brake lever while ensuring both pistons slid out evenly. I stopped once or twice to to wedge one while the other "caught up". Done!

Both pistons came out and believe it not, using just a hand towel and brakeKleen, I wiped off the crude from the pistons and they're bright, shiney and new!!!

I will be paid back in kind by Karma though, if not this, it'll be the next project (my carbs).

The XJ Gods let no one off easy!

 

Grease Gun is the way to go!
It forces out the Piston.

The main reason that the Piston sticks is Crud Buildup in the grooves of the Bore where the Caliper Piston Seals seat.

Remove the Piston.
Remove the two Seals.
Clean the Caliper of all traces of the grease.
Using a scraping tool ... scrape-away all traces of Buildup in the grooves.
Scrape to bare aluminum.
Clean the whole Caliper with Brake Kleen Spray.

Lube the grooves, seals and piston with fresh Brake Fluid before re-assambly.

 

Why does everyone insist on using a grease gun when the pressure from the brake system is more than enough to push the pistion out? I just cant justify spending the extra time (and money if you don't have the grease gun) cleaning the caliper body out. And you have to get it spotless as I would think you don't want grease and brake fluid mixing. Just my 2 cents.

 

I agree with dannzeman. I think the only reason you would use a grease gun is if the brake fluid pressure simply wasn't enough. THEN the grease gun would come in handy as a last resort. As for the air method...YIKES! All I can see is a hole in the garage wall that I would have to repair. Would make for some good video footage though!

 

That works just fine, as well. Assuming your brake system is still fully assembled, bled, and has reasonably fresh fluid in the lines...

But.... if you have the caliper already off the bike, it takes 10-15 seconds tops to pop it out with a grease gun, followed by a few seconds of paper towel action (grease cleans up very easy from the caliper)... why not go that route? Grease guns are cheap - 15-20 bucks. a tube of generic grease is maybe another 4-5 bucks. The only catch is that you have to plug off the hole where the banjo bolt goes.. maybe with a similar-size bolt (10x1.25mm)

 

The grease gun approach is the universally applied method for getting out a STUCK Caliper Piston.

If you can get it out with Brake Hydraulic Pressure ... its moving; not stuck.

A STUCK Piston can be quite a fight getting out. Some may require having to lock-on to the shadow of oxidation, near the end of the Piston, and "Exercising-it" back and forth to get it moving.

Just remember the key to movement is the surface of the cut channels the Seals seat into.
Getting ALL the oxidation and crusty build-up off the inside diameters of those two channels is what's going to make your Brakes operate like they should when the job is done.

In some cases it takes some real heavy-duty scraping to get the build-up scraped off.
But the build-up is what is making the Bore "Out-of-round" and causing the Piston to bind, be lazy or stick.

 

I hope all you guys using grease guns for hydrolic removal of a sstuck caliper piston are doing a complete system clean and flush of your brake system before puting everything back together.

Even the smallest amount is left in the system is dangerous. You caliper can freeze up on you during heavy breaking. I had it happen before on a truck about a week after I had it worked on at a shop. That's how they did it and it almost got me killed.


I recommend that you stay away from using grease and just use the hydrolics from the master cylinder. It may be messy but you don't have to worry about not getting all the grease out of the system.

 

Fair warning, but: you apply grease right to the bleeder valve, with the banjo bolt hole blocked off. No other brake components are exposed to grease.
so all you have to clean up is the piston bore, which probably needs some good scrubbing anyway, and the passage in the bleeder valve, which can be done with a squirt of brake or carb cleaner.

 

Bumping this thread. Reduce, reuse, recycle.

Just dealt with this myself, and yes, it was suggested to reconnect the caliper to the master cylinder. Problem was, the system had been drained and the naughty bits removed from the bike, so that wasn't an option. Besides, it wasn't working too well when it WAS connected to the master cylinder, so I really kinda doubt it would have helped much. I tried to avoid using the grease gun, but I didn't appear to have much of a choice.

Two different people using two different air compressors failed at the task. That puppy was NOT coming out without a fight. So, one cheap handheld grease gun (courtesy of Harbor Freight) later, which the sheet of paper says can generate 4500psi, the piston inched its way out.

And yes, I do intend to clean out the guts of the caliper, thankyouverymuch.

/O RLY?
//Ya RLY.
///Kthxbai