Brake Pistons not coming out?

[Stockko]

Hi guys

Just changed all the seals on the front brake callipers and cleaned everything up. I've refitted the callipers however the pistons won't push out, there no pressure behind the brake lever? Bleed the system to the point where there's no visible air bubbles coming out, any help would be appreciated.

[magg]

Master cylinder mounted on handle bar while trying to bleed?

[Stockko]

Yes

[jedidude04]

Did you use red rubber grease/soak the seals in brake fluid?

There might be air somewhere, i had to go through an entire bottle of brake fluid to fully bleed the system.

[magg]

Suggest you remove the master cylinder from the handle bar and position it horizontal while pumping the level. Air will get trapped at the hose to master cylinder junction because it is a high point when the master cylinder is mounted on the bar. Once you get any piston to move you can press it back into the caliper while stopping the other pistons from moving out, forces fluid and air back up into reservoir. I find it easier done with calipers and master cylinder off the bike, pistons packed out while pumping horizontal mater cylinder and pistons pressed back into calipers as they move out, until the lever is hard are no air is forced back into reservoir when piston are pressed into caliper.

[arsey30]

Try bleeding from the banjo bolt on the master cylinder. Wrap rag around the hose, then slacken bolt and pump lever, hold lever in and then tighten bolt. Do this several times to get rid of the air in the highest point in the system.

[dobbslc]

Try a syringe with a bit of tube on the bleed nipples and suck out the fluid, it will pull out any air with it. What's probably happening is the trapped air is just compressing as you pump the lever and not shifting any fluid. Newly build calipers or new lines is a PITA to bleed most of the time!

[Stockko]

Thanks all for the replys, I tired bleeding from the banjo bolt on the master cylinder which did the trick!