Bleeding some shimano brakes... is the hose blocked?

mac_man

Been trying to bleed a shimano M485 brake, I've followed a video found on youtube... basically take off resevoir cap, apply tube and bag to bleed nipple. Open bleed nipple, squeeze brake lever, close nipple, release brake lever. repeat to clear bubbles. This seemed to work initially. However there's now no more oil flowing through the tube, although the resevoir is still full

Is this a blocked hose or something?

I was messing about with the brakes earlier whilst the pads were out and squeezed the lever and the pistons came out slightly. seemed to be a fair amount of gunk behind them... could this be what's blocking the hose?

supersonic

It's always best to clean the pistons before a bleed, and alwats push them all the way home and use a spacer to stop them moving when bleeding.

Don't push them all the way out! Clean with very mild detergent, rinse and dry well. A tiny smear of mineral oil on the piston can help.

Try bleeding again.

mac_man

I think I might have pushed one of the pistons all the way out though...

Basically the oil is not being pushed through the hose when I squeeze the brake lever... there's no oil coming out the bleed nipple at all... which is making me think there is a blockage of some kind.

supersonic

Push the pistons as far in as you can, add the spacer and squeeze the lever again.