How to Remove stuck brake piston ?

[fjrider]

Got brakes off off an older 1981 gs850l, and brakes are locked. ANy tips for pushing the piston out safely so I can clean and rebuild the calipers? Thanks.

 

[LarryA_Texas]

It may not be the best way, safest or even recommended, but I just hook it up to a working master cylinder and pump gently until the hydraulic pressure forces it out. It's messy but it works.

 

[Dogma]

Larry's method is the 2nd way to try, if you have an air compressor to try first. If you do try compressed air, be careful. The piston will blow out hard enough to do damage, take out an eye, etc.

 

[fjrider]

Thanks for the tip. I spoke to someone else today wh recommended air pressure from compressor and it worked great. Used the small orifice air nozzle on the air compressor, and pressed it into/against the brake caliper threaded opening (where brake line usually feeds in). Gave it air pressure little by little, and wallah ! the piston moved slowly out. I tried in on another caliper and gave it too much pressure, and the piston popped out like a gun sound and went about a foot away from the caliper.

Wrap it in rags when doing it just in case.

Thanks for the advice....now I have two ways - brake fluid from master cyclinder, and air pressure.

 

[BassCliff]

Hi,

Yes, be careful using an air compressor to blow out the brake piston. Wrap necessary parts in a rag in such a way to do no damage. I have put the caliper in a vice and then used a rubber tipped air nozzle to blow air into either the bleeder port or brake line port (depending on which is open, which can be blocked) and pushed out the piston. Incrementally increase the air pressure until the piston "blows" out. Don't try to just run up the pressure all at once.


Thank you for your indulgence,

BassCliff

 

[sschering]

I've heard a grease gun works well.. find a zirt that fits and pump away..

 

[BassCliff]

Hi,

Yes, a grease gun will work but they're messy.



Thank you for your indulgence,

BassCliff

 

[sschering]

Hi,

Yes, a grease gun will work but they're messy.



Thank you for your indulgence,

BassCliff

Wrapped in a towel it won't be so bad..
It's better than air blasting brake fluid all over the shop or a flood of Dot 3 on your work bench.. Grease tends to stay in one place

 

[fjrider]

Thanks for all the advice. I tried the air method and noticed two things:

1. It works.
2. It is kinda messy if you are not careful. When blowing the air in, sometimes excess fluid blow out. So, it helps to wrap it all in rags.
3. Too much pressure too quickly causes piston to push out very quickly, sometimes with an alarming "pop" and with some velocity. Wrap it in rags, and blow slowly.

I am hoping to find a small manual fluid hamd pmp (lie grease gun) that I can load with brake fluid and just pump it out slowly like it is design to do. Maybe I'll adap and old master cyclinder and see how it goes.

 

[Nessism]

Air is simple and fast. Use a rag to protect the parts, and yourself, first. Grease is messy and unnecessary, assuming you have access to a compressor.