cabby Posted November 14, 2011 Report Share Posted November 14, 2011 Put this topic in this section as it's a bleeding brakes issue and not specific to a particular make, anyway... Sons bike had squealing brakes, thought, new pads should sort that, it didn't all it got me to notice was the pots were hardly moving, so split the caliper, removed pots, replaced with new seals and pots. Replace fluid, try to bleed and getting no pressure at all in the caliper, can't even get fluid to flow out of the bleed nipple. Am I missing anything ? I have removed the piston from the MS and it looks fine, well to my eyes that is....ideas folks ?? Quote Link to comment Share on other sites More sharing options...
stevecollie Posted November 14, 2011 Report Share Posted November 14, 2011 Am I missing anything ? Just some "Brain Cells" Quote Link to comment Share on other sites More sharing options...
chewy Posted November 14, 2011 Report Share Posted November 14, 2011 did you "prime" the slave cylinder somehow get fluid behind the pistons. best done on assembly of pistons into thier pots. once thats full..fluid coming out of the nipple you can back bleed using a syringe ensuring that master cylinder piston is fully back. Quote Link to comment Share on other sites More sharing options...
cabby Posted November 14, 2011 Author Report Share Posted November 14, 2011 did you "prime" the slave cylinder somehow get fluid behind the pistons. best done on assembly of pistons into thier pots. once thats full..fluid coming out of the nipple you can back bleed using a syringe ensuring that master cylinder piston is fully back. I did put some behind the pots, yes. Quote Link to comment Share on other sites More sharing options...
clay Posted November 14, 2011 Report Share Posted November 14, 2011 (edited) did you "prime" the slave cylinder somehow get fluid behind the pistons. best done on assembly of pistons into thier pots. once thats full..fluid coming out of the nipple you can back bleed using a syringe ensuring that master cylinder piston is fully back. Just check, that there is no ball bearing, beneath the bleed nipple,, before back bleeding. Other wise you could end up having an early shower,,,, belive me, done that, got the tee shirt Edited November 14, 2011 by clay Quote Link to comment Share on other sites More sharing options...
cabby Posted November 14, 2011 Author Report Share Posted November 14, 2011 Back bled, loads of air coming up right til there was none and MS was full, but still no pressure at the caliper Quote Link to comment Share on other sites More sharing options...
scraggydog64 Posted November 14, 2011 Report Share Posted November 14, 2011 I have had some long nights in the garage bleeding brakes, the rear brake on my last mont took weeks to get right. In the end, following the recommendation of a knowledgeable friend I got a Gunson Easy Bleeder (about Quote Link to comment Share on other sites More sharing options...
cabby Posted November 14, 2011 Author Report Share Posted November 14, 2011 Yes rear brakes are a nightmare, though I wouldn't have thought my front would've been so tough. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted November 15, 2011 Report Share Posted November 15, 2011 Th proiblem with a number of brakes is that they have "up loops" in the hydraulic pipes that trap pockets of air. All you do when trying to bleed with the lever / pedal is move the air pocket about but not far enough to expel it. - It floats back to the top of the up loop when the pedal / lever is released. This is usually a worse problem on back brakes. Can you suspend uor bike so there is a continual rise or fall in the pipe or can you remove a compoent and raise or lower it to get the same effect. On some bikes with twin slave cylinders on the same caliper (as most bike now are) the bleed nipple is in some cases on the lower cylinder and the air collects trapped in the upper cylinder. Bck filling with a large syringe or easybleed is the best solution (I prefer not to drill caps)but parking the bike in the right position overnight or for a few hours can get the air to the reservoir naturally. Another thing to check for is corrosion in the slave cylinder seal grooves. This distorst the seals and although they may not leak it prevents them controling piston movement correctly. Cheers Quote Link to comment Share on other sites More sharing options...
cabby Posted November 15, 2011 Author Report Share Posted November 15, 2011 Have tried all various types of methods, unfortunately I had to split the caliper to get the old pots out, last night I tied the lever to the bars but still to no avail. I have ordered another m/s piston. One question though, when I pull lever in and out I get air bubbles coming up ?? Should that be happening or is that a sign of m/s piston seal gone ??? Quote Link to comment Share on other sites More sharing options...
tankygsy Posted November 15, 2011 Report Share Posted November 15, 2011 In order: Release the adjuster on the brake lever so the master cylinder piston is fully contracted. Back bleed with a syringe. When you think you've forced enough through it and it's spraying out the reservoir slow the pressure on the syringe down a bit so the reservoir fills up. Tighten bleed nipple. Replace reservoir cap, make sure the reservoir is completely filled so that it oozes out when you put the membrane back in. Now with the system sealed up put a spanner on the bleed nipple and while holding the brake lever in open the nipple. Close the nipple and let the brake out again and repeat once more. This will push the pistons out to the disk. You should have a brake now. If not don't worry, fill the reservoir up again and repeat the bleed process just with a wrench and the pumping process. If you don't have a brake now something isn't quite right somewhere and needs investigating. I find after I've bled the brakes it takes a bit of use for them to fully firm up, once they do I then adjust my brake lever to where I want it. You have to release the adjuster to bleed them, if not the piston in the master cylinder will not draw fluid in the suction side of the reservoir. Quote Link to comment Share on other sites More sharing options...
cabby Posted November 15, 2011 Author Report Share Posted November 15, 2011 Still no joy, can it be the caliper seal rather than the ms seal possibly, bearing in mind I have split the caliper. Quote Link to comment Share on other sites More sharing options...
tankygsy Posted November 15, 2011 Report Share Posted November 15, 2011 If the caliper piston seal was leaking you would clearly see fluid coming out if it. Quote Link to comment Share on other sites More sharing options...
cabby Posted November 15, 2011 Author Report Share Posted November 15, 2011 Fair point, someone else said that also, I replaced it tonight anyway, and still not a single bit of movement in the caliper Quote Link to comment Share on other sites More sharing options...
tankygsy Posted November 15, 2011 Report Share Posted November 15, 2011 (edited) Are you sure you are bleeding enough air out of it, I force about 60 - 70ml through the line to ensure the air is evacuated. Edited November 15, 2011 by tankygsy Quote Link to comment Share on other sites More sharing options...
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