Remove seized rear brake master cylinder piston?

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Rear brake was binding so loosened caliper nipple and seemed I could release pads by levering them open. So I figured caliper pistons are likely free. Pulled the rear master cylinder and removed the boot and circlip and noted corrosion likely from water ingress. The end of the piston is there but the spring is not pushing it out. Any ideas how to get it out, or is it likely not salvageable with a rebuild kit?

[FJmonkey]

 Hook the hydraulics back up and push it out from behind.

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Hook the hydraulics back up and push it out from behind.

How do I pump fluid into the banjo connection? What could I use to pump it with? Thanks.

[5speed]

Hook the hydraulics back up and push it out from behind.

How do I pump fluid into the banjo connection? What could I use to pump it with? Thanks.

bolt the brake hose back on and use the brake pedal.
If that doesn't work, remove it from the bike, heat the body up and try and blow it out using compressed air.

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bolt the brake hose back on and use the brake pedal.
If that doesn't work, remove it from the bike, heat the body up and try and blow it out using compressed air.
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Pedal wasn't offering any resistance before I removed it so I think the piston is probably pushed in near the maximum travel. If it does move it again it will likely just push it further in. I'll try compressed air. Perhaps installing an M10 x 1.25mm threaded grease nipple into the banjo bolt thread and pumping it out with a grease gun might work. Anyway I get the idea thanks.

[krusty]

IMHO grease gun method works best.

[5speed]

Pedal wasn't offering any resistance before I removed it so I think the piston is probably pushed in near the maximum travel. If it does move it again it will likely just push it further in. I'll try compressed air. Perhaps installing an M10 x 1.25mm threaded grease nipple into the banjo bolt thread and pumping it out with a grease gun might work. Anyway I get the idea thanks.

it won't push the piston in any further..the brake fluid is between it and the master cylinder housing. The grease fitting idea works..I just don't like the thought of grease in the brake system..even if I cleaned it a dozen times murphy's law says I will miss some. lol

[ribbert]

The grease fitting idea works..I just don't like the thought of grease in the brake system..even if I cleaned it a dozen times murphy's law says I will miss some. lol

It's not going to be in the "system" just the master cylinder and that's pretty easy to clean thoroughly once the piston's removed. My mechanic recommends kero or petrol to dissolve the grease (mostly because you are likely to have some already) compressed air and finish off with a cheap can of Brake Cleaner to get rid of any residue.

He also recommended this tutorial as being very helpful and said it would save him a lot of typing.

https://www.youtube.com/watch?v=cCo85w2OdWo

Noel

[5speed]

It's not going to be in the "system" just the master cylinder and that's pretty easy to clean thoroughly once the piston's removed. My mechanic recommends kero or petrol to dissolve the grease (mostly because you are likely to have some already) compressed air and finish off with a cheap can of Brake Cleaner to get rid of any residue.

He also recommended this tutorial as being very helpful and said it would save him a lot of typing.

https://www.youtube.com/watch?v=cCo85w2OdWo

Noel

I was referring to my luck at cleaning it..remember schleprock from the flintstones? lol

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Had difficulty sourcing an M10 x 1.25 grease nipple in Canada though. All I have come across so far seem to have an M10 x 1.0 thread. Have ordered a new master cylinder on aliexpress instead.