Topic: NOTHING can remove my brake piston

[Hondawggie]

1980 cb900 Custom Honda.   Rear brake piston, aka 'puck', is stuck in place.
This is the 12-year-not-ridden bike I brought back to running condition in the past few weeks.

I noted that when I went to bleed the rear brake, the piston would not move and I was using a special high-speed vacuum brake bleed tool -- and getting nowhere.

So today I removed the caliper and noted that the puck was stuck in a half-way-on position, ie. the puck was not fully recessed in the caliper bore but the puck was also *not* extended out far enough to cause the pads to put friction on the brake rotor.

I then disconnected the brake hose from the caliper and allowed all the fluid to drain out of the caliper.  It was quite full, so I know I'm getting fluid from the master cylinder.  I removed the bleed nipple and the hose bolt and left them off.

After the caliper was drained of fluid, I removed the rubber apron dust seal from the outside of the puck, and used a brass wire toothbrush to clean around the exposed part of the brake puck.  I then tried pushing the puck into the caliper bore with both thumbs-- would not budge.  So I got a small block of wood and lightly tapped on the puck and the puck did in fact recess a bit into the caliper bore, but still would not move like it should.

I then got 120psi compressed air and THE F-ING PUCK WOULD NOT MOVE A MILLIMETER........
f|_|ck.

Okay, got determined and put a vise grip onto the rim of the puck (the part that does NOT ever slide inside the caliper bore).  Then I put the vise grip into a bench vise, the vise grip is now vertical and is tightly clamped in my bench vise, now I can grab the entire caliper for leverage and turn it to get the puck rotating in the bore.

NOTHING.   my vise-grip was an AMERICAN made one, not chinese, we are talking U.S. MUSCLE VISE GRIP here, clamped tightly on the outer exposed rim of the brake puck, I'm 210 pnds and muscular, I've got both hands on the f-ing caliper trying to get it to turn while the brake puck is 100% stationary, in the vise grip, while the vise grip is clamped into my bench vise.

NO THE PUCK AINT GONNA MOVE.

I just don't get it -- both of the front calipers on this bike disassembled easily.

I try 120psi air again on the caliper after squirting it full of Amazing blaster and putting Blaster on the outer rim of the puck where it descends into the caliper bore.

NOTHING.

So right now, I have the entire caliper submerged in 50/50 acetone and automatic transmission fluid.  My plan is to leave it in there one week.  Before totally submerging the caliper, note that I had previously removed the bleed nipple and the hose port bolt and left them off for the week-long submerge in my 50/50 sauce.

Anyone have any ideas how to get this puck out of the friggin caliper?

[754]

 I yse my grease gun adaptor... 1500 psi gets it every time...

[scottly]

+1 on the grease gun method. I've used it several times in the last few months. Pistons that wouldn't budge with compressed air pumped right out, with no drama.

[754]

 A lot safer too...

[MCRider]

+3 on the grease gun. I had one terminally stuck, air wouldn't budge it. I was very sceptical about the grease gun method. But what did I have to lose? Threaded it in a few threads, gave it a few pumps and the piston started to move. Moved about 1/8 inch with each successive pump, i couldn't believe it.!

Do It!

[Jerry Rxman Griffin aka MuthaF'er]

+4 on the grease gun. Just do it dammit 

[trueblue]

+5 on the grease gun, I have also used the mastercylinder on my bike to push the pistons out, bleed out the cylinder and have it off the bike AWAY FROM THE PAINT and keep squeezing the brakes, just keep the reservior full, easier to clean the caliper up afterwards than grease, and gives about the same pressure.

[Hondawggie]

+3 on the grease gun. I had one terminally stuck, air wouldn't budge it. I was very sceptical about the grease gun method. But what did I have to lose? Threaded it in a few threads, gave it a few pumps and the piston started to move. Moved about 1/8 inch with each successive pump, i couldn't believe it.!

Do It!

Okay tomorrow I'm buying a grease gun.


I have 3 Questions:

(1) Is the grease gun screwed in (somehow?) to the
- bleed nipple's threaded hole
- OR  is the grease gun hooked up to the brake hose's threaded hole?

(2) How do I block off the brake hose threaded hole if the grease gun gets connected up to the bleed nipple?

(3) do I need a special adapter to connect the grease gun hose to the brake caliper's port, whichever port that is from (1) above?

I said 'a week's dousing of the brake caliper' as I figure a week's 'cooling off'
period will kill the desire I had today to smash the borgas frat p.o.s. caliper with a
huge mofo sledge hammer.  If I can figure out how to hook up a grease gun
I'm not gonna wait.

[MCRider]

The end of the grease gun hose is a metal piece about 1-1.5 inches long. It will unthread from the end oif the hose. This leaves the rubber hose with a male thread ending. The thread is not the same as the thread in the caliper bleeder hole. Or the hose hole, either.  However it will thread in and catch a couple of threads, just turn it in by hand till it stops, don't force it.

To plug the other hole, you'll need a 10mm bolt of the proper thread. I think various motor mount bolts or you may have to go to the hardware.

No special adapter. Justpump the gun.

For me this was so easy I kicked myself for not trying it sooner. Hope it works for you.

[Bob Wessner]

This worked for me as well. I don't know if it made any difference one way or the other, but I put a couple of turns of Teflon plumber's tape around the grease gun threads before threading it to the caliper.

[DH]

I did mine thru the nipple. Blocked the hose port with appropriate
size/thread bolt, and was able to lightly force the grease gun fitting over the end of the bleeder. Takes ALL the drama out, as long as the nipple has been loosened previously and the bleed passage is clear

[MCRider]

I did mine thru the nipple. Blocked the hose port with appropriate
size/thread bolt, and was able to lightly force the grease gun fitting over the end of the bleeder. Takes ALL the drama out, as long as the nipple has been loosened previously and the bleed passage is clear

Wow, I hadn't thought of that!

[754]

 I have not tried using the threads on the greasegun pipe, but know it seems to work.. but there is a chance you could hurt the threads.
 I make adaptors on the lathe, that match the correct threads, AND have a seat taper, so I can go into the brake line hole, OR against the shoulder, like on a MC. then the other end is tapped for a grease fitting..
 I should make some up to sell.

 if there is fluid in the caliper the greaseGlob, usually just falls out, if it cottage cheese in there, you have to wipe it out..
 Its a tool that is actually fun to use.

 A long time ago , I watched in amazement as they pumped out the track adjuster on a TD 15 bulldozer.. .. with an ordinary grease gun!!  then I found out how much pressure they make.. like 1500-2000 psi!

[Jordan]

+1 on grease gun took 5 min. worked like a charm

[Hondawggie]

Okay after listening to the tried-and-tested advice, I bought my grease gun, $16.99, one large-size 14oz tube of lithium grease (the cheapest type of grease) for $2.99, and a 12" rubber hose for $6.99 to extend/relocate the tip of the grease gun (the tip that apparently will fit around the bleed nipple on the calipers, thanks for sharing that).

The rubber extender hose will extend the 'business end' of the grease gun from the gun's short metal rod to the end of this 12" rubber hose so I can sit down on a stool and drink a cold one whilst leisurely pumping and applying 1500psi pressure to my stuck brake puck.  Without the rubber extender hose I'd otherwise have to orient the grease gun vertically above the caliper's bleed nipple and have to stand up to pump the gun.

I also got a 10mm x 1.25 thread-pitch bolt to block off the brake hose port, $1.99 for a pair of them bolts.   $30 total for the kit.

Now I gotta go the the garage and try out this approach.  If this 1500psi grease gun dont work, and keeping in mind the caliper has now been 100% immersed in 50/50 acetone+atf for one full day -- if this don't work I don't know what will.

[Bob Wessner]

Well, if it works, you'll only get but one swig of the beer. 

[Hondawggie]

Well, if it works, you'll only get but one swig of the beer.  

Not even one.   It was a crack of the tab to open the can meanwhile pumping my new grease gun raise the can up to take a drink, 'plop' whats that oh just the puck falling a few inches into my drip pan.

about $0.25 of grease, a look of astonishment, an undrunk cold one.
Pretty efficient.  Very humbling.


So I thought a bit and realized 'why isn't the rear brake's master cylinder pressure able to move this puck while the grease gun did it in seconds'


- is it the much greater leverage due to the surface area of the grease gun's plunger being pushed by the arm of a big dummy, compared to the much-smaller surface area of the master cylinder plunger?

- what's the best way to get the grease out of the inner channels of the caliper?

[MCRider]

Great news. Amazing huh?

Don't know about the pressure.

Wipe as much out as possible. Then some degreaser on a cloth, as little as possible. Takes more time to clean it than to get the piston out eh?   

[Hondawggie]

Great news. Amazing huh?

Don't know about the pressure.

Wipe as much out as possible. Then some degreaser on a cloth, as little as possible. Takes more time to clean it than to get the piston out eh?   

Will do, degreaser.
Pretty darn effective this grease gun and at $30 much cheaper than buying a used caliper off ebay and praying its in better shape.

Is it possible that I have compromised my master cylinder's inner rubber seal parts on the master cylinder piston by pumping and pumping the brake pedal with a severely stuck brake puck?   I'm wondering if I should just assume the worst, I spent a lot of time trying to bleed it before discovering the stuck puck being the problem.

Or do the master cylinder inner rubber seals hold up real well.

[Markcb750]

That Archimedes dude had his #$%* together didn't he?

[MCRider]

Great news. Amazing huh?

Don't know about the pressure.

Wipe as much out as possible. Then some degreaser on a cloth, as little as possible. Takes more time to clean it than to get the piston out eh?   

Will do, degreaser.
Pretty darn effective this grease gun and at $30 much cheaper than buying a used caliper off ebay and praying its in better shape.

Is it possible that I have compromised my master cylinder's inner rubber seal parts on the master cylinder piston by pumping and pumping the brake pedal with a severely stuck brake puck?   I'm wondering if I should just assume the worst, I spent a lot of time trying to bleed it before discovering the stuck puck being the problem.

Or do the master cylinder inner rubber seals hold up real well.

Besides didn't you need the grease gun for something else anyway. Both my lawnmower and my rider lawn mower take grease (they aren't the newest machines).  

My bet is your MC is fine, if it isn''t obviously leaking out of the piston/seal area.

[754]

 Be careful putting a bolt in the brake line hole, if you botton it, you can damage the seat, bolt should seat on the cone, or be shorter, and seal with a washer under the bolthead..

[MoMo]

That Archimedes dude had his #$%* together didn't he?

That is a reference I never thought I'd see .....Larry

[trueblue]

I always use methylated spirits for the final clean of any brake components before reassembling, it doesn't affect the rubbers and removes any residual grease or oil which will affect the rubbers

[Hondawggie]

Got the mstrcyl all cleaned, the puck's o-ring groove was gunked up bigtime, cleaned the groove with my brass O-ring picks.   I then used 000 steel wool to polish off a whole bunch of oxidation in the bore and also in the o-ring groove.

Thanks TB about the 'methylated spirits' I should try that.  I currently use IPA.
I cleaned the rubber parts with IPA (isopropyl alcohol, I learned to used IPA when cleaning parts and o-rings on ultra-high vacuum semiconductor manufacturing machines, IPA cleans with no residue, doesn't hurt the rubber parts).  

Puck slid easily in/out of the bore, then I put dot 3 in the bore and o-ring groove, then put the now-cleaned o-ring in the bore, tapped in the puck, reinstalled the dust boot around the puck, hooked up the brake line to the caliper, put my speedy-bleed vacuum bleeder on, started bleeding, NOTHING.

Tap-tap-tap on the footbrake, NO FLUID enters my speedy bleed bottle that's connected to the caliper's nipple.

So I then yanked the master cylinder.


I got a baddie.







If you've ever had a m/c apart, you will instantly recognize the circlip and the washer on the shaft of the plunger.  Those 2 parts close off the end of the bore where the m/c piston slides in-and-out.

Did I remove the circlip and washer from the m/c?  NOPE.  The circlip etc. fell into my hand as I removed the brake pedal linkage from the m/c plunger.

The circlip and washer must have fell off a long time ago all by themselves, look at the oxidation everywhere, on the plunger/shaft, the washer, the circlip, the m/c piston and its bore.

These photos were snapped AFTER I spent a noteworthy amount of minutes with a wire brush brushing lots of oxidation and junk off of the parts in the photos.   If you'd see these parts fresh off the bike before my wire brush treatment you'd have said 'no good toss  em.'

I just wanted to see the parts to figure out how, with the rest of the bike in extremely good shape, and the front brakes only required caliper cleaning and bleeding -- I wanted to see how a 9k mile bike can puke its master cylinder circlip.  Because when that happened more than 12 years ago, I suspect brake fluid leaked out of the m/c bore and down onto the plunger shaft and the other bits.  Brake fluid being highly corrosive would explain why there is more rust on this one small part than the entire rest of the cb900's parts *combined.*

I'm gonna clean/remove the m/c piston and *try* to salvage the bore.  Otherwise I have to hit ebay and find a 'new' m/c.