Author Topic: Brake caliper - piston stuck (Read 18272 times)

anotherCB · « **on:** April 05, 2011, 12:38:41 PM »

I just disassembled my front brake, but cannot get the piston out. I think I could just hook it back up to the system and "pump" it out with the brake. Or is there an other way? Doesn't seem to move at all, tried to push it in but just won't move. The bike is a K7. Thanks.

cobra2411 · « **Reply #1 on:** April 05, 2011, 12:42:31 PM »

I ended up hooking mine up and pumping it out. When they're free a quick blast of air from a compressor will pop them out very quickly but if they're seized...

I also hit mine with penetrating oil and heated it with a propane torch to expand it. Hook it up, bleed it out and start pumping. It should move. If not penetrating oil and heat. Also you'll want to have a pan under it to catch the fluid as it pukes out.

I've got a few calipers that I have to go though and rebuild so I can do a dual brake setup... Not particularly looking forward to it.

Open to other suggestions too...

Radam · « **Reply #2 on:** April 05, 2011, 12:45:35 PM »

I've always used an air compressor. Make sure you have it wrapped up in a towel or something because they come out at high speed.

Gaucho · « **Reply #3 on:** April 05, 2011, 12:53:23 PM »

Grease gun in the bleeder screw and a regular bolt to plug where the brake line goes. Pop goes the weasel.
Gaucho

cobra2411 · « **Reply #4 on:** April 05, 2011, 01:16:07 PM »

How do you attach the grease gun? Also do you know off hand the thread size of the brake fitting?

anotherCB · « **Reply #5 on:** April 05, 2011, 02:13:00 PM »

Thanks guys, will try the compressor first and if that doesn't work, hook up the unit and "brake it free".

swellguy · « **Reply #6 on:** April 05, 2011, 02:20:24 PM »

Quote from: cobra2411 on April 05, 2011, 01:16:07 PM

How do you attach the grease gun? Also do you know off hand the thread size of the brake fitting?

10mm grease nipple. Grease gun nozzle loosens up, slip it over the nipple then tighten the nozzle up. Then pump away. Slowly but surely it comes out. Did mine last night. Lots of grease to deal with afterwards, though.

Steve F · « **Reply #7 on:** April 05, 2011, 03:45:42 PM »

The grease gun is WAAAAAAAy safer than compressed air, if you can get compressed air to do anything at all. Also, grease won't get all over everything like brake fluid can, and it won't destroy painted surfaces either. The clean-up is two minutes.

nokrome · « **Reply #8 on:** April 05, 2011, 06:45:56 PM »

i recommend compressed air and maybe a little heat if its really seized,
as far as the danger factor, come on folks, we are motorcycle riders, we live for danger!!! just dont aim it at your face when you are doing it

i tried the grease gun method before, all it did was make a big mess

octagon · « **Reply #9 on:** April 05, 2011, 08:36:19 PM »

it's easy to break your fingers using compressed air so keep them out of path of the piston.

plippo · « **Reply #10 on:** April 07, 2011, 07:50:45 AM »

I have used successfully a Blind hole bearing puller that I recently purchased from HF for the hub bearing job.
Worked a charm. I bit of heat with the heat gun and came out in one shot...:-)

RickB · « **Reply #11 on:** April 07, 2011, 08:07:10 AM »

I had a friend make a grease nipple that went into the bleed screw and we greased it out. No way it was coming out any other way.

MCRider · « **Reply #12 on:** April 07, 2011, 08:33:55 AM »

The grease gun was my savior. Unthread the head from the hose, leaves a male threaded portion. Its not the correct thread for the caliper, but it will catch a few threads. Pump away and the piston comes out slowly and tenderly.

Air is great after its unstuck, but as mentioned BE CAREFUL it will come flying out like a bullet.

anotherCB · « **Reply #13 on:** April 07, 2011, 05:58:54 PM »

Will go for it tonight and let y'all know how it went. My grease gun gave up on me so will use the brake fluid method...

MCRider · « **Reply #14 on:** April 07, 2011, 06:08:44 PM »

Quote from: anotherCB on April 07, 2011, 05:58:54 PM

Will go for it tonight and let y'all know how it went. My grease gun gave up on me so will use the brake fluid method...

Obviously that should work. remember that when the piston comes out there will be fluid everywhere, that's a big cavity behind the piston. And you won't have near the progressive control the grease gun gives. I can see the piston breaking free and shooting out like the air does. Keep it covered up and away from things you don't want hurt or stained by the fluid.

splitt · « **Reply #15 on:** April 07, 2011, 08:32:39 PM »

If you try to use an air compressor, wrap it with an old towel like radam said & place it inside a 5 gallon bucket to keep the piston from damaging something. Also, don't get your fingers in front of the piston when it comes shooting out of there. I tried 140 psi on mine, but it wouldn't budge. The only way that I was able to get mine out was the grease gun method. The grease gun method is slow & controlled.

BeSeeingYou · « **Reply #16 on:** April 07, 2011, 10:13:37 PM »

I have never had to use any other method than using the MC. I don't see why you need to screw around with grease, air, the associated mismatched threads, cleaning grease out of the small passage, and flying pistons. The piston will not come shooting out and fluid will not go flying everywhere as long as you go slow and easy on the lever. Once the piston reaches a position where it is almost free the O ring will lose it's seal at some point on the piston and you will get a small amount of fluid leak and then you lose pressure. This is when you stop and just grab the piston and pull it the rest of the way out. This has worked for me on one bike that sat for 25 years and another that sat for 20.

TwoTired · « **Reply #17 on:** April 07, 2011, 10:29:03 PM »

Quote from: srust58 on April 07, 2011, 10:13:37 PM

I have never had to use any other method than using the MC. I don't see why you need to screw around with grease, air, and the associated mismatched threads and flying pistons. The piston will not come shooting out and fluid will not go flying everywhere as long as you go slow and easy on the lever. Once the piston reaches a position where it is almost free the O ring will lose it's seal at some point on the piston and you will get a small amount of fluid leak and then you lose pressure. This is when you stop and just grab the piston and pull it the rest of the way out. This has worked for me on one bike that sat for 25 years and another that sat for 20.

+1
I've always used the MC to get the piston out. It's never ever come flying out. At some point the puck is released, which you can easily catch with your hand. When the piston itself goes past the seal, it leaks really bad, and you pull the rest out with your fingers over a catch can. I usually have a can of Brakleen nearby to immediately wash off any sort of splash or splatter on painted surfaces.

The lastest job was on a bike that sat for 25 years (77-Cb750F). The MC just had crystals in it. So I rebuilt the MC first, then bled the system and pumped out the pistons using C clamps on the piston that moved the easiest to keep the dual calipers in balance. By the time one started leaking, they both came out with fingers.

FYI
Cheers,

bryanj · « **Reply #18 on:** April 07, 2011, 11:18:38 PM »

I agree with TT, if its still on the bike use the Master cyl, I did use the grease gun method when i had a "collection" of calipers in a box and it was quicker than fitting each one up and bleeding, likewise when i had 10+ masters to strip i found it made it easier if i played an oxy acetalene flame down towards the circlip first as it disposed of all the crud and corrosion---but not worth it for a one off

faux fiddy · « **Reply #19 on:** April 08, 2011, 01:50:55 AM »

Quote from: MCRider on April 07, 2011, 06:08:44 PM

Quote from: anotherCB on April 07, 2011, 05:58:54 PM
Will go for it tonight and let y'all know how it went. My grease gun gave up on me so will use the brake fluid method...
Obviously that should work. remember that when the piston comes out there will be fluid everywhere, that's a big cavity behind the piston. And you won't have near the progressive control the grease gun gives. I can see the piston breaking free and shooting out like the air does. Keep it covered up and away from things you don't want hurt or stained by the fluid.

+1 I was going to say, fluid will need to be cleaned up. Best to prepare in advance. (pan, rags, Soap and water, etc.)

MCRider · « **Reply #20 on:** April 08, 2011, 05:35:55 AM »

Quote from: tree fiddy of industry on April 08, 2011, 01:50:55 AM

Quote from: MCRider on April 07, 2011, 06:08:44 PM
Quote from: anotherCB on April 07, 2011, 05:58:54 PM
Will go for it tonight and let y'all know how it went. My grease gun gave up on me so will use the brake fluid method...
Obviously that should work. remember that when the piston comes out there will be fluid everywhere, that's a big cavity behind the piston. And you won't have near the progressive control the grease gun gives. I can see the piston breaking free and shooting out like the air does. Keep it covered up and away from things you don't want hurt or stained by the fluid.

+1 I was going to say, fluid will need to be cleaned up. Best to prepare in advance. (pan, rags, Soap and water, etc.)

Yup, the grease gun may be messy, but grease stays put pretty well. You'll know where it is and its easy to wipe out. It won't damage what little it may get on. Someone said 2 minute clean up and I'd agree with that. I resisted using the grease gun for a while, frustrating myself till i did. So easy.

c(b)hris · « **Reply #21 on:** April 08, 2011, 05:58:23 AM »

As far as the mess goes just plan ahead and wrap the whole caliper loosely with some shop towels. Soaks up the brake fluid and protects the piston from shooting out.

anotherCB · « **Reply #22 on:** April 08, 2011, 06:02:53 AM »

Since I hadn't a grease gun handy last night I used the brake fluid method--got it out in no time, the spill wasn' bad since i was prepared. Then I got carried away, what started as a brake pad job ended with me holding the triple tree in my hands! Reason is that I wanted to polish the forks, paint the speedo-tach bracket, do a better job hiding my wires in the light, check wheel bearings and clean the wheel anyways, so while I had the caliper off, I just went for it all. Too bad though, around midnight after a couple beers, i pushed the caliper pistin back in the wrong way, flat side out...That means I have to do the brake fluid method AGAIN

MCRider · « **Reply #23 on:** April 08, 2011, 07:23:59 AM »

Quote from: anotherCB on April 08, 2011, 06:02:53 AM

Since I hadn't a grease gun handy last night I used the brake fluid method--got it out in no time, the spill wasn' bad since i was prepared. Then I got carried away, what started as a brake pad job ended with me holding the triple tree in my hands! Reason is that I wanted to polish the forks, paint the speedo-tach bracket, do a better job hiding my wires in the light, check wheel bearings and clean the wheel anyways, so while I had the caliper off, I just went for it all. Too bad though, around midnight after a couple beers, i pushed the caliper pistin back in the wrong way, flat side out...That means I have to do the brake fluid method AGAIN

That sounds like par. We've all been there.

krusty · « **Reply #24 on:** December 17, 2011, 08:42:42 PM »

This morning I read through this topic and found the solution to my problem of a stuck piston. Having tried all the usual like air pressure, heating, soaking in various potions (which had worked before) I tried the grease gun.
I'm sold! It was dead easy and took a matter of a few minutes.
Having had success with my CB750F piston I then had a go at the rear brake slave cylinder of my 1960 Suzuki 250TA. Same result. Fantastic! Thanks guys.

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Author Topic: Brake caliper - piston stuck (Read 18272 times)