Brake advice

[scott]

Hi guys, just replaced the seals, pistons and the rubber o ring on my rear calliper (z1000a2)...the fluid is coming out of the bleed nipple although quite slowly but there feels like no pressure on the pedal. I have no leaks or weeps and air did come out of the nipple. The pistons seem to move ok as well. I made sure the relief hole in the master cylinder was clear to. Is the lack of pedal pressure due to a faulty piston in the master cylinder?

[z1bman]

its probably the seal in the master cylinder has probably been damaged as the only time it travels its maximum travel is when you bleed the brake & any corrosion or contamination in the cylinder will take the edge of the seal

[PAULJAC47]

Hi Scot, how did you bleed the brakes? in my experience they can be a right sod,i use a vacumn pump to pull the fluid through,previous to this i used to try all the old methods but always seemed to not get all the air out,to test your master cylinder blank off the output and see if you get firm pedal,,Good luck Paul J

[scott]

Paul, the only time I've had problems bleeding the back was due to clogged bleed nipple and relief hole, apart from that it's always been easy for me.....6 pot tokicos have been a pain in the arse though...I'll try to blank it off first, if that fails then must be as z1bman says....dodgy piston seal...cheers guys

[Bill Newman]

Scott - I dunno if this helps.

When you rebuilt the calliper did you get enough lubricant on the seals/pistons, because if you are reusing the same pads the first push of the pedal will move the pistons some distance. If the seals are new they can grip the piston and roll out when it moves. Plenty of fluid and a really gentle first pull/squeeze/push to get the pistons located....

[scott]

All that went fine bill....if the seal has rolled would it not weep at all?

[Fred the Zed]

Hi Scot, how did you bleed the brakes? in my experience they can be a right sod,i use a vacumn pump to pull the fluid through,previous to this i used to try all the old methods but always seemed to not get all the air out,to test your master cylinder blank off the output and see if you get firm pedal,,Good luck Paul J

+1 Sounds like an airlock. try back filling carefully with a syringe. That's how I bled my Shed's rear brake

Fred

[scott]

Thanks Fred, I'll give that a try

[scott]

Thanks for the advice guys ...it will be stored in my sieve like memory for future reference...the primary cup seal in the master cylinder had decided to find a new home down the side of the spring instead of on top of it....replaced the cup and had it bled up in minutes