Topic: Stuck Caliper Piston

[hopterfixer]

I have seen this topic come up several times and wanted to throw in my experience.  I had a stuck caliper piston, sitting 11 years, water in the line, rusty, STUCK.  I used the grease gun method and it worked pretty slick.  Remove the brake line from the caliper but leave the bleeder screw tight.  Remove any fittings from the end of your grease gun hose.  Thread the hose directly in to the brake line hole on the caliper just a little, squeeze the grease gun handle and watch the magic happen.  Any other methods?

[grumburg]

Tried several. Never found one that works better.

[ic455]

Are you all using hand powered grease guns?  If so, are they full-sized or the miniature-type?
Plan on trying this out (when I get my bleeder repair kit), just wanted to know how everyone is doing it.

[Bob Wessner]

I used a smaller gun, but only because that's what I keep around for lubing the swing arm.

[johnny-from-bel]

There is no better mehod

[grumburg]

I have seen this topic come up several times and wanted to throw in my experience.  I had a stuck caliper piston, sitting 11 years, water in the line, rusty, STUCK.  I used the grease gun method and it worked pretty slick.  Remove the brake line from the caliper but leave the bleeder screw tight.  Remove any fittings from the end of your grease gun hose.  Thread the hose directly in to the brake line hole on the caliper just a little, squeeze the grease gun handle and watch the magic happen.  Any other methods?

Only difference is I have a metric Zerk fitting I keep just for the occasion. Thraeds into brake line hole. Just use a standard gun.

[hopterfixer]

I used a full size, hand powered grease gun, but it did not take a lot of muscle to push it out.  Using a metric zerk to thread in is a great idea, no chance of messing up the threads. 

[Toyman321]

I used an air compressor on mine....  thing sounded like a gun went off when it finally gave

[Dave K]

Yep, I have done that too. I though had my hand in the caliber with a rag to catch it. Of course when it flew out of there, it pinned my hand to the other side of the caliber. I made a few new faces and words and learned a lesson! OUCH!

[Chris Liston]

I used an air compressor on mine....  thing sounded like a gun went off when it finally gave

Same here,  Just place a towel folded over a few times on your work bench and place the air nozzle into to brake line fitting and POP.  Sounds like a gun but does that piston come out

[anubiscycle]

When I do this I pull the caliper from the bike (Duh), remove the brake line and take one of the allen head mounting bolts (that holds the two halves together) and put it in the brake line hole. Then remove the bleeder and make sure it is clear of crap. re install it loose and pump away with the grease gun.

[liaudio]

I've never had mine to the point where it needed a grease gun. What I have done and what most of you already know already is below.  I am assuming that your master cylinder is ok.  If not, this method wont work.  If the bike has been sitting long enough to seize the piston, it might be a good idea to rebuild the master cylinder.  Maybe not. 


Leave everything assembled. 

If you took off the caliper to rebuild it, put just the bleeder and the brake line back on. 

If the caliper is still on the bike, just take the caliper mounting bolts off so the pad and piston are totally free to move.

Have extra brake fluid ready and just start pumping away at the brake lever. 

Add brake fluid if it starts to get low. 

If the piston doesn't look like it's moving outwards at all, you may have to try something else. 

If the the piston appears to be moving, just keep pumping away, adding fluid as necessary.

Eventually, the piston will fall out of the caliper.

No more stuck piston!

[Raul CB750K1]

Never found an occasion when "works like a charm" applies better. Thanks for the tip guys!!!

A picture is worth a thousand words....

[dusterdude]

oh yea,the grease gun method is slicker than snot.

[Tom in Newcastle......Ontario]

Just used the grease gun method........got a metric bolt that fit the brake line hole,( I think it was a 10mm)cut the threads off,drilled a hole 7/32 all the way through the threaded section, and tapped a 1/4  28 NF thread and than added a standard grease zerk.......worked great,excellent idea guys Thanks

[Steve F]

I've tried both the compressed air and the grease gun, and the air method was successful only once.  Beside it being dangerous and maybe will damage your piston once it goes flying across the room at mach 1, I'll never do that again nor would I recommend it.  The grease gun method is totally safe. 

[sandcastcb750]

I force it out with the master cylinder, why make it difficult?

By the way, it is usually the brake pad that is stuck/not moving as opposed to the piston. After you remove some meat or corrosion from the brake pad, the brake works great.

[Dave K]

On my K3, the pads float freely on top of the piston and on my K3 I can't think if away that they could stick. But, my piston certainly will stick. Especially, when I have been negligent in changing brake fluid. I have always used compressed air to clear it, but it certainly shows here that there is more than one way to skin a cat.

[Raul CB750K1]

I force it out with the master cylinder, why make it difficult?

By the way, it is usually the brake pad that is stuck/not moving as opposed to the piston. After you remove some meat or corrosion from the brake pad, the brake works great.

In my case, it was a spare cylinder, so I had no master cylinder available. The pad was stuck too, but you can apply WD40 adn as it protrudes you have some leverage to bash it or move it until it breaks loose. The piston is another business, there is no easy way to get a good grab of it and turn it or pull it. Before I lost my patience, I soaked it with WD40 -even through the caliper holes- and decided to do something else until I search on the forum for some tip. This forum proved invaluable again with this tip. As you can see in the picture, you don't even need to tap anything; when you remove the zerk fitting, the gun hose ends in an M10 tip that bolts straigth into the caliper. To close the other hole, you either use the bleed nipple or use one of the M10 caliper bolts as I did -again following some of your advice-

[swan]

Wow, thanks everyone!

I had six calipers with frozen pistons. Two came out with compressed air and went off like a gun. The remaining four would not budge. I read this, bought a 10mm zerk fitting and a grease gun today and removed the last four easily with this method. Thanks again!

[JAG]

Okay..  Newbie to all this stuff, so bare with me..

When I purchase my bike it had no front brake at all..  I open up the master cylinder, saw that there wasn't any brake fluid, so I figure, DUH, that's why the brake doesn't work. Added some fluid, and started pumping away. After about 100 or so pumps from the brake lever it started to stiffin up and give resistance, so I figured it was working.. Did it a few more times, and now the brake is not allowing the wheel to move at all!

So took apart the caliper and what not, got to the piston and realized I couldn't get it out, so I just forced it back in so atleast my wheel would turn freely..

With using this grease gun method to force the piston out, is that also allowing for some lube to be applied to the inner sides  to allow for free movement of the piston so it won't freeze up allowing the wheel to not move? Or is that after all the position for the brake fluid?

I tried to bleed the brakes while it was froze against the wheel, but the darn thing is frozen in place and I have no earthly idea on how to set it free without rounding off the edges of the bleeder.

I hope I've been clear with my issue. Do I need to just get a re-build kit or is there a way around all of that?

Thanks for the help!!!

[Dave K]

You really need to get the bleeder loosened. I would try a 6 pt. wrench or socket. If you have an air impact, try that on a low setting and build up the air pressure till it breaks loose.

[TwoTired]

With using this grease gun method to force the piston out, is that also allowing for some lube to be applied to the inner sides  to allow for free movement of the piston so it won't freeze up allowing the wheel to not move? Or is that after all the position for the brake fluid?

Grease just contaminates the caliper innards.  You will have to clean every bit of that grease out of the caliper before using it.  I always use the master to pump out the caliper piston.  This will require bleeding most of the air out of the system, and possibly cleaning/rebuilding the master cylinder first. (If it's not working right now, it's not going to work any better after the caliper is working.)   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.  Then clean and rebuild that, too.
In the FAQ, is a front caliper rebuild walk through.

As for the caliper bleeder,  A six point socket is required to get that off.  If it is at all stubborn, too much torque will break it off. You can try soaking the threads and the valve seat with a penetrating oil.  If you no longer have the rubber boot over the bleeder valve, the seat is corroded, too.  So put oil inside that bleed hole too and wait 24 hours.  If the bleeder valve breaks off anyway, then you can still use the caliper, but you will have to bleed the entire system through that tiny bleed hole at the caliper.  This can take a couple days as you reposition the bike to allow the air to rise to the high point the system.

Cheers,

[InaneCathode]

I use air and a pile of towels/rags to catch the projectile when it comes out.
The ONLY reason why i dont use the MC (really you should, its easier and better on the system) is i hate brake fluid. Its nasty. Has a weird smell, texture, and it always gets on everything.

[JAG]

Okay tried messing with the front caliper again to no avail.

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.

I tried different copper fittings laying around the garage to try and hook up to the air compressor to it. Nothing really worked.. Tried and hook the line back up and tried the squeezing method again, nothing. 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.

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??

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


I'll address it some more tomorrow.. Thanks for all the indepth help TwoTired.