Topic: Stuck Caliper Piston

[InaneCathode]

Just for giggles, wear gloves when you're playing with brake fluid. It's glycol based and will absorb through your skin. Its known to cause reproductive harm so, keep that in mind

When you squeeze the handle its not doing anything to the piston?
You 'did' take the caliper off of the bike before you tried ejecting it right?
When you squished it back in you might have put it in crooked and forced it a bit crooked. Its likely stuck in the bore, that happens tho, no worries.
You'll have to bleed the brakes out before you can try to eject the piston again.
At this point i dont think penetrating fluid will free the bleeder, have you tried heat? Just get the bleeder glowing slightly then get it CLAMPED in the vice and twist that #$%*er out!

[TwoTired]

After working with the caliper as stated before, I continually squeezed the lever until the piston popped out , but it never let go and locked up my wheel, so I took it back off and used a C-clamp to push it back in. I must have messed up when I did that because now I cannot get it to budge what so ever.

You must remove the caliper body from the bike to extract the caliper piston.  Let it dangle from the brake hose over a catch pan.  The piston probably won't move now because of air in the lines.  It compresses ,whereas fluid will not.

Took it off and just squeezed the lever, and realized that there wasn't much fluid flying out. I could put my finger over and feel the air push out, but no real gush of fluid like I thoght would shoot out.. Is the line clogged? Also noticed the brake fluid was of a brown coloration.

Brown fluid bad.  Use new clear fluid.  Sounds like you still have a lot of air in the lines.

As far as the bleeder valve I tried the six point socket method- nothing. I went as far as tighteng the bleeder in the vice, and it never broke free.. Concerning the penetrating oil; is there a brand name, specifics??

Mix up 50/50 with acetone and auto trans fluid.

As far as the master cylinder, it did bubble up, and even shot out a time or two when I released the lever,

Means you built up air pressure in the system and then it blew the fluid back when it was no longer held by the lever/piston.

so I assumed everything was in order, but now I think there is a hefty amount of air in the line seeing as how I was pumping away at it and seeing no break fluid fly out of the brake line- that feeds into the caliper..

Yep, hefty amounts of air.  Did you check the FAQ, yet?  There's bleeding tips in there.
If your master is working, you can prime it by removing the brake line fitting at the master, holding your finger over the end so you can get fluid in front of the master's piston.  You should definitely be able to feel the pressure then.  If not, then it's master rebuild time.

Cheers,

[JAG]

Well thanks to you guys, I got er done, so to speak!!

-I drained out all the bad fluid, shot a little air through it, to make sure.

- hooked up the the caliper to the line, danglin, of course. and started pumping away.

-since I could not, for the life of me, get that bleeder unstuck, I had my step dad sit there with a 10mm wrench, and after 5 pumps, he would release the line, and watch the air shoot out. 5 pumps more, release and once again letting it shoot out..  We did this until the piston just fel out on the floor..  Oh man, you should have seen the crud that was built up!!

-Cleaned it all out, made sure it slid in there nice and comfy, and this time we mounted it all up there, and repeated the process as of, with concerns to the bleeding.. We did it till there was no more air in the line.

-Now I haven't road tested it, but he sat on the back of the bike, while on the center stand, to elebate the front tire, and I spun away, hit the break and it would catch, spun away, and pulling the lever once more, and let it stop the wheel. So even though I haven't road tested it, in theory it should work..

I'm so friggin happy, I had a beer to celebrate!

So cheers!!

And thank you!

[InaneCathode]

Good way to test is to give the brake a good HARD squeeze and see if it frees up right after you release the brake. Another good test is to park the bike in the sun and feel the brake pressure after its warmed up real hot. It should still be regular brake pressure, not self pressurizing. Its better to find that out before you're out on the road without a bleed screw wrench :O

[troppo]

well i`ve just had to something similar, and reading some of the horror stories about using air, i`m wondering what you guys were thinking?
i blew mine out with air at work (about 130 psi) i had the complete caliper (both halves) in the vice with a heap of rag wadding, plugged the air in and pressed the trigger, you screw the original bolts back in and clamp one half og the caliper in the vice (not too hard), put plenty of rags inbetwen the two halves of the caliper and pump it full of air. When its blown out a little, release the air, unwind the bolts a bit and repeat........
It may take a little longer but it will work most times, worked on the front brakes of a 78 escort that had sat in the weather for 15 years) and you wont have bits of brake flying around the room..
Soaking in WD40 or similar will help if its really bad.
Now before you shoot me down, i know not everyone has a compressor, but if you go to a local workshop with a sixpack under your arm i dare say you could convince someone to help you for five minutes
cheers all
troppo

[fixahonda]

At the bottom of the master cylinder reservoir, there are two holes to feed fluid to the system and allow air to get out.  The one closest to the brake hose has a very tiny hole at the bottom.  If you slowly move the brake lever, bubbles should pop out those holes, provided there is still air in the lines/ system and you have given them time to rise to that high point.  If that tiny hole is blocked, forget about getting the brakes to work right. That hole is quite tiny, something like .010 inch or so. Bigger is NOT better. So, don't just drill it out. Once you have the master working correctly and the system bled of air then simply keep adding fluid and pumping out the caliper piston until it pops free of the caliper body. 

Thank you so much for this bit of info. My master cyl was full of what looked like a mix between powder and congealed brake fluid. I cleaned the crud out of it, cleaned the hole closest to the handle and installed the rebuild kit. The other hole I though was blind as it appeared to have nothing but metal at the bottom. I tried bench bleeding it but as you could imagine it didn't work. I was about to head to the shop today to give it another go but thought I'd read the forums a bit before I went over. Glad I did!
I cleaned the small hole with a strand of wire and it bench bled perfectly!

My hats off to you...

[sbc1320]

I always used air and have done many cars this way. Always put a piece of wood in between and keep your hands out. The piston pop out against the wood and then I clean everything. Lubricate the oring and piston with brake fluid, then push back in by hand usually. Sometimes you will have to compress with clamp. If a dual piston and one is stuck, then I use several different layers of wood or paneling and step them out. Just shoot the air and one will move then the other, pull out one piece of wood and do it again and eventually both pistons will be out. Works fantastic.

[blake255]

Just want to throw my $.02 in on this one.  I had read about the air compressor method of freeing a frozen piston.  Figuring I needed a compressor around the shop, I went and bought one for $200.00.  Got it home, hooked it up, got the caliper, put 2 & 2 together and got…NOTHING.  It didn’t even budge.  I worked on it for about an hour each of the next two days.  I was bummed.  So I jumped on here and found this thread.  The next day I called a few local industrial bearing and supply houses to find a 10mm grease fitting and borrowed a grease gun from the maintenance shop at work.  Took it home threaded it up, pumped it once, pumped it twice, DONE!  Wow, that was easy.  Moral of the story: air compressor ($200) + 2 hours = nothing; 10mm fitting ($.25) + 30 seconds = success.

Yes, the fitting only cost 25 Cents.  What a deal.  But since then I’ve noticed most auto parts sell an assorted pack of metric grease fittings for a couple of bucks.  I’d say it’s worth getting the right fitting.

[low-side]

This method works great for bikes that have been sitting a long time.  If I need the piston out of a system that is working properly, I lock the MC lever to the bars so it won't lose excessive amounts of fluid and push the piston out on the bench with the compressor after wrapping it up with a towel - no fluid anywhere and no extra work.  If the system has been sitting and is internally corroded, I try air first.  If that doesn't work, it's time for the grease gun.  If it is so nasty that you need to use a grease gun grease contamination isn't an issue because it will need completely rebuilt anyway.  The grease gun hose uses a tapered thread, so I just screw itin until it begins to snug.  I've never had a stuck piston that the grease gun couldn't remove. 

[TwoTired]

Why is a grease gun preferred over hydraulic fluid?

[TomC]

Hi TwoTired
     "Why is a grease gun preferred over hydraulic fluid?"
     I have two words for you Leverage & Leakage.
     That said the only time that I have needed to use the grease gun method was on a 1969 Plymouth Barracuda 6 cylinder with disk brakes. Mopar did a really bad job of chroming the cast iron pistons. Clean up was a real pain!
          TomC in Ohio

[TwoTired]

So, you are saying the ram cylinder and longer handle of the grease gun make more PSI than the Master on the bike?

Any quantification of the pressure difference?

Cheers,

[TomC]

So, you are saying the ram cylinder and longer handle of the grease gun make more PSI than the Master on the bike?

Any quantification of the pressure difference?

Cheers,

Hi TwoTired
     I went out to my garage and did some quick measurements. Given the same pressure on the end of the lever my POC grease gun should produce 2.3 time the pressure that my Honda 14mm master cylinder would produce. I believe that I can put more pressure on the end of the lever of the grease gun than I can the master cylinder. Say 2 times +/- 1/4. That would be 4 to 5 times the pressure. Then I forgot to post my reply.
     Yesterday I received the January 2009 issue of Cycle World. Check out the question and answer on page 86.
          TomC in Ohio Who hopes he never sees a caliper piston so stuck that I have to use this method again.

[ev0lution7]

greese method worked for me 2 loved it

[grumburg]

Just want to throw my $.02 in on this one.  I had read about the air compressor method of freeing a frozen piston.  Figuring I needed a compressor around the shop, I went and bought one for $200.00.  Got it home, hooked it up, got the caliper, put 2 & 2 together and got…NOTHING.  It didn’t even budge.  I worked on it for about an hour each of the next two days.  I was bummed.  So I jumped on here and found this thread.  The next day I called a few local industrial bearing and supply houses to find a 10mm grease fitting and borrowed a grease gun from the maintenance shop at work.  Took it home threaded it up, pumped it once, pumped it twice, DONE!  Wow, that was easy.  Moral of the story: air compressor ($200) + 2 hours = nothing; 10mm fitting ($.25) + 30 seconds = success.

Yes, the fitting only cost 25 Cents.  What a deal.  But since then I’ve noticed most auto parts sell an assorted pack of metric grease fittings for a couple of bucks.  I’d say it’s worth getting the right fitting.

I don't even spend a quarter on a grease fitting. The grease fitting in the rear swing arm fits perfectly in the caliper.

[RM81]

Grease gun worked for me.  Thanks for the tip!

Does anyone have a source for 10mm x 1.25 grease fittings?  And what's the best way to remove all the grease afterwards?  I got my caliper soaking in some simple green, but there's still some grease in the threads/hole where the brake hose attaches.  It's a dual piston caliper.  I've already gone through a can of brake cleaner.  Any suggestions?

[coyotecowboy]

Starting fluid, wd 40, basically anything petroleum based.  Gasoline, solvent (mineral spirits) take your pick


[edit] I guess wd 40 is silicone based, but it will still loosen gun grease

[Porscheguy912]

Hole eee $hit.
This worked awesome.
Some of the best advise i have gotten from this site.
10mm grease fitting $1 and $3 for a new grease tube.
Success in 2 minutes with no bleeding knuckles...... Priceless.
Thanks!

PS: reason compressed air does not work so well is because air compresses and fluids don't.
You get the double whammy with this one; grease is thicker than air (it helps seal nasty rusted bits and it exerts more pounds per square inch of force to the piston).

The little secret is that the grease fitting has a one-way check valve in it. = Grease into the caliper with the only way out via the path of least resistance.... the piston.

In my case the pad is what was stuck, once it was out of the picture the piston pulled right out.

[Sparked]

I was fighting with a stuck piston last night, and after I got frustrated I checked the forum and look what I find.  Picked up a grease gun today and worked slick. Thank you everyone.  Now to rebuild the MC.

[camelman]

Awesome trick.  I'll try it next time.  I recently broke a piston loose by removing the bleeder and brake line, putting the caliper in a huge vice, and used a cheater bar on the handle of the vice.  I had so much force on the cheater bar that when the piston finally compressed into the caliper, it blew a large drop of brake fluid out of the caliper hard enough to blow through two tightly wadded paper towels!  I'm glad I wasn't standing in the way.  I resorted to this because I was blowing out the brake lines when I tried to remove the piston by squeezing the master cylinder tightly.  I got the piston out with the master cylinder after I loosened it in the vice, but it was a ball of rust, so I through the whole thing out.

Word of caution on the grease gun method.  Make sure to remove and clean your o-ring after doing this.  The o-ring rubber can stand up to alcohol (brake fluid), but not to petroleum.  If you do not clean the grease out of there, then it will degrade the o-ring over time.

Camelman

[patrickd]

Went to Carquest, bought a 10mm zerk, screwed it in where the brake line goes, put grease gun on it pumped it full of grease and out it came slick as can be.

[ev0lution7]

we have all had great luck with that method i think its totally awesome and very safe...
recomended it to my auto mechainc friends and they looked at me like i was crazy i told them it was safe and worked good... they just said:

BUY a new one... HA buy a new cb750 caliper.. i rebuilt mine... painted it and it looked better than new!

[Toxic]

I only had sucess with this method after bleeding the grease out of the bleeder fitting.

I think I was not able to get enough pressure built up as the grease was compressing the trapped air.

Once the air was bleed out it worked great.

[Cajun]

I will try this on a stuck one I have.  Thanks

[OldSkool]

Wow, this would have been so much better than the air compressor method that resulted in the piston hitting me right in the family jewels. If anyone in my neighborhood saw me in the garage that day I hope they got a good laugh. I'm just glad I didn't have to go to the hospital, it would have been a tough one to explain.