Stuck rear caliper piston

[chazchuzzlewitt]

typical... go to check & replace my rear brake pads and find out what was causing the sqealing I was getting... right-side outer pad was worn down almost to the bracking and the piston is stuck in the out position and doesn't want to budge... tried bleeding the moving it but it's still removing to give more than a tiny amount... any tips?!

[Denis]

Hi chaz

One side hey ...rebuild both calipers ! Get rebuild kits, take both rear calipers off and clean/polish/refit the flex parts in them. Never done it ? I can help.

When it happens on one side, the other is also due. Sure, you can fiddle in there and maybe even break a piston but this kind of binding cannot bre cured with banging or magic fluids.

Boenne chance 

Denis

Paris, France

[s class]

Chaz,

Agreed  rebuild the calipers.  Its not that difficult to do yourself.  Just work carefully to avoid dirt ingress.  And please only use genunine benz caliper overhaul kits.  The cheap spares shop stuff just doesn't fit, or if it does, it just doesn't last.  If that doesn't appeal to you, remove the calipers and send them in to a brake repair specailist.  They usually don't chard much to overhaul calipers, so long as there is no pitting in the bores. 

Cheers, Ryan

[chazchuzzlewitt]

thanks for the replies. I did manage to push it back in with a G-clamp, there I could see the rubber seal is shot on one side.

[Denis]

Hello fellows

What most people do not know is that calipers release the brake pads with more than just one taking his foot of the pedal (hydraulic presure goes to zero). The rubber seal that chaz saw merely protects the cylinder and piston from rust and abrasive materials. About a cm into the bore, a FLEXIBLE brake seal (rectangular cros-section) flexes OUT when the brake is applied and back IN (returns to a non-deformed state) when the brake peal is released. Brakes will drag more or less permanently when this seal can no longer take back its shape. That is why one MUST overhaul old calipers, not just replaces the "ugly" seals

regards !

Denis

Paris, France