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General Category => Maintenance => Topic started by: pict on August 13, 2021, 05:05:04 PM

Title: Remove seized rear brake master cylinder piston?
Post by: pict on August 13, 2021, 05:05:04 PM
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?
Title: Re: Remove seized rear brake master cylinder piston?
Post by: FJmonkey on August 13, 2021, 06:26:18 PM
 Hook the hydraulics back up and push it out from behind.
Title: Re: Remove seized rear brake master cylinder piston?
Post by: pict on August 13, 2021, 06:37:55 PM
Quote from: FJmonkey on August 13, 2021, 06:26:18 PM
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.
Title: Re: Remove seized rear brake master cylinder piston?
Post by: 5speed on August 13, 2021, 07:00:52 PM
Quote from: pict on August 13, 2021, 06:37:55 PM
Quote from: FJmonkey on August 13, 2021, 06:26:18 PM
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.
Title: Re: Remove seized rear brake master cylinder piston?
Post by: pict on August 13, 2021, 07:51:10 PM

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.
[/quote]

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.
Title: Re: Remove seized rear brake master cylinder piston?
Post by: krusty on August 14, 2021, 01:33:51 AM
IMHO grease gun method works best.
Title: Re: Remove seized rear brake master cylinder piston?
Post by: 5speed on August 14, 2021, 07:27:14 PM
Quote from: pict on August 13, 2021, 07:51:10 PM



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
Title: Re: Remove seized rear brake master cylinder piston?
Post by: ribbert on August 14, 2021, 10:38:33 PM
Quote from: 5speed on August 14, 2021, 07:27:14 PM

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

Noel
Title: Re: Remove seized rear brake master cylinder piston?
Post by: 5speed on August 15, 2021, 05:50:18 AM
Quote from: ribbert on August 14, 2021, 10:38:33 PM


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

Noel
I was referring to my luck at cleaning it..remember schleprock from the flintstones? lol
Title: Re: Remove seized rear brake master cylinder piston?
Post by: pict on August 15, 2021, 08:24:23 AM
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.