Rev 4t Front Disc Bleed

[gazzaecowarrior]

Please help me as I've drawn a blank. My front brake felt a bit spongy so I thought i'd bleed the system and get any air out. I've bled hundred of brakes but just can't seem to get any real pressure back in the system. It just about starts to apply the pads when the lever is pushed right in. Also what comes out of the nipple doesnt seem to be as big as usual.The brakes were fine before I bled them so I'm certain it's not the seals. I havent adjusted the levers at all. Could it be a blockage ? Usually when I bleed the front brake you see a few little bubbles in the resevoir but I havent seen any. Could there be a blockage here ? I have compressed air and was thinking of bowing it through from the nipple end and clearing the system and starting again. Would this be a good idea ? Just to confirm I'm not doing anything really stupid when I bleed the brakes I do the following :

- Put pipe on nipple and release nipple.

- Remove master cylinder cover and pump brake.

- When no air bubbles appear in pipe I keep lever pushed in and tighten nipple.

I also tried to do it as I would my hydraulics on my mountain bike i.e. from the nipple up backwards. I didn't seem to be able to push anything through at all. It does seem like a blockage.

I'm sure Im doing things right but I can't get the pressure up. Your advice would be much appreciated. Thanks. Gareth

Edited September 2, 2010 by gazzaecowarrior

[betabonkers]

Gareth you dont need to touch any nipples all i do is take the top cap off and just tickle the levers free play and you should start getting bubbles rising to the top, if not ill sort it at the trial sunday if i aint to hungover. Andy will be there though he could sort it.

[gazzaecowarrior]

Nice one jason. I am certain Ive got a blockage though somewhere. Im going to have a good look at it tommorow and saturday. If I've got no success I may give you a ring saturday. I've still got your number.

Gaz

[betabonkers]

no problem mate.

[deandev]

As it happens ive just sorted out my boys beta rear brake today. i did the same as you and had no fluid going through the system so i removed the bleed nipple which turned out to be blocked, 10 minutes with a bit of wire and some carb cleaner sorted out the blockage, 5 minutes later job done. may be the same for you? Cheers

[b101uk]

I also tried to do it as I would my hydraulics on my mountain bike i.e. from the nipple up backwards. I didn't seem to be able to push anything through at all. It does seem like a blockage.

There should be some clearance between the end of the master cylinder piston and the lever adjuster that pushes the master cylinder piston in, the clearance is there to allow the master cylinder piston to return fully allowing fluid from the reservoir into the master cylinder chamber, if there is no clearance then the master cylinder piston gets held in a bit thus the little hole that allows fluid from the reservoir into the master cylinder chamber is blocked off/restricted.

Hence the low volume/velocity of fluid arriving at the bleed nipple meaning any air in the system wouldn

[gazzaecowarrior]

Thanks for all your advice. I will try everything tonight and let you know. I allready have a degree of play between the lever pusher and the piston so i don't think it is that but I will certainly give it a go. Thanks.