Caliper rebuild

I rebuilt my master cylinder but the caliper was still dragging on the disk, so I took the caliper apart. Major issues here, The piston barely moves. I can't imagine how I could even get the brakes to work! Long story short, I can't get the piston out.

I know I once saw a pictorial, step-by-step rebuild instruction page on this site, but I can't find it. Does anybody know where it is?

Also, can I take the whole caliper and just soak it in something to try and get the parts free? This thing is a mess!

 

You need to rebuild the calipers. The best,and safest, way to remove the caliper is to take them off the bike put a grease nipple into the hole the bleeder valve comes out of. Then block the hole the brake line goes into with a bolt and pump it up with grease until the caliper pops out. You will have people tell you to use air this may or may not work. But the air method IS dangerous as the caliper can come flying out and hurt someone if you are not careful.

 

To get mine out (both of them). I just used the master cylinder to pump brake fluid into the calipers one at a time. I used a bolt and a copper washer to block the brake lines one at a time at the splitter while I pumped the handle. Worked like a charm and didn't grease up my whole caliper piston.

Just make sure you keep feeding the MC with brake fluid.

If you have a hydraulic pump on your bike already, why would you go to the trouble (and mess) of using a grease gun?

 

+1 on the MC pump method

 

Problem is you them get brake fluid all over everything. I personally prefer the grease method. Cleanup is not as messy as brake fluid!

 

so the piston itself comes out with enough pressure heh? How do you go about putting it back together??

I'm about to tear my 550 Maxim caliper apart because its sticking as well. Any other words of advice to those who never done this yet? All I've read from around here was to be certain everything is 'lick-clean' shiny clean inside as well as the piston itself polished while its apart. I'm more nervous about putting the dang thing back together correctly

I am looking for something like this as well and haven't found anything... seems important enough I'm surprised it doesn't get floated around like Fitz's rear brake check thread

 

Due to age it may be more prudent to replace piston with a nice new stainless steel one and renew cailper seals at the same time.

When refitting clean and lubricate piston seal and caliper with new brake fluid, make sure its square to the cailper and push into caliper body. A small amount of force may be required but they do usually go back quite easily.

 

For re-assembly of new piston with new seal into caliper:
I ended up using a bench vise with padded jaws and a wooden block on the piston. Slowwwllly pressed the piston in.

It made a god awful groan as it fitted itself into position - but -no leaks and everything works!

 

The reason that everyone's had a slightly different "reassembly" experience is the same reason I haven't done a "how-to" yet--

the brake calipers are different from model to model to model; between 550s, 650s and 750s, Maxim and Seca.

There are at least 4~5 different calipers spread across the XJ range.

 

I actually just got done blasting the piston out - I used the air compressor at my job with a rubber nozzle fitting pressed in, and jammed some rags under it to catch it. Eased out slowly and when it finally came out the POP was a little startling, but altogether pretty straightforward.

 

Well I've tried both methods, and that damn thing aint comin' out! I managed to get it almost all the way out with brake fluid, but it just stopped and refuses to budge.

I ordered a housing off e-bay, and will rebuild that with a new piston, seals etc. There just comes a point where it makes more sense to spend an extra $25.

 

using this method, i managed to get one of my pistons on one caliper out. following that, every time i squeezed the brake lever, fluid shot out the side no longer holding a piston.

what's the method for blocking that off, so that enough pressure will build up on the other side?

(there ARE two pistons per caliper, right? or am i reading the exploded diagram's forked lines wrong?)

 

The Grease Gun Method is highly effective.
If the Caliper hasn't been removed from the system; using the Master works --> IF ... the Master is healthy and Pumps well.

Extreme Measures:

Add a Tablespoon of Water and Plug the Inlet Port and Close the Bleed Port.
Heat.
The water will Boil at 212-Degrees.
Steam Pressure will force the Piston out.***

+++
DANGER
+++

Observe Extreme Caution.***
Eye and Projectile Hazard.

 

my master cylinder is, indeed, fairly healthy, and seems to pump quite well. but on every pump, the brake fluid is squirting out of the side of the caliper no longer holding a piston.

(i am about to rebuild the master cylinder also, but only as a maintenance measure, not because it is in dire straits.)

for that matter, the pistons and piston seals seem to be in good order, but i am also replacing them as a maintenance measure.

it seems like the issue of squirting fluid will continue regardless of what measure i use, be it grease, boiling water, or just pressure from the master cylinder, unless i can find a good way to block off the hole that is now present from the one piston that has been removed.

 

Can you not replace and partially hold the already removed piston in place with rods and 2 x G Clamp assembly so that the other (stubborn) one pops out?

 

yes, i suppose i can! i'll try that.

 

If you look VERY CLOSELY at the Piston, ... you'll see a "Shadowed Area" at the Front.
You can Grab the SHADOWED AREA --> ( The Very end of the Piston that never encounters the Seal ) <-- with Vice Grips or Channel Locks and PRY the Piston out.

At the very least, ... you can Torque-it straight ... and/or ... Lube it with Brake Fluid to Un-seize it.

If you grab it tight enough to leave Tool Marks, ... KEEP the Tool Marks within that Narrow Band that does not retreat into the Bore far enough to encounter the SEAL.

 

I thought I'd share the method I ended up using:

I split the calipers (the 700 has two calipers per piston, not sure about other models). On the side with the hose attachment, I plugged the hose hole with one of the bolts that holds the calipers together. On the bleeder screw side, I just left the bleeder screw in place as a plug.

Then, on both sides, I plugged one fluid transfer hole with a bicycle inner tube, and used a bicycle tire pump with a rubber needle fitting to "inflate" the other fluid transfer hole. All four pistons popped out with very little effort using this technique.

Tip: point the piston away from your face, and preferably at a pile of rags or something. They shot out with some amount of force.

Anyway, my calipers are super clean, with new piston seals and fluid transfer o-rings, and new pads. On to the master cylinder!

 

Look-in the Caliper Seal Retaining Channel.
Make sure the whole channel is perfectly clean.
It does not take too much foreign matter lodged in them to cause the Piston t bind.