How Do You Syringe Bleed Brakes

[hoggyf]

Struggling to bleed my brakes at the mo so tried using a syring but i can't get it to work no matter what I try - any advice??

[lowbrow]

Front or back? Have you changed the pads?

[hoggyf]

back, replaced the amster cylinder but it just won't bleed up so thought i would try a syringe (as has been mentioned on other topics) but when i press the syring it just ends up blowing off the bleed nipple (yes the nipple is open before anybody dives in!!!)

[steve1979]

Try filing up the reservoir, then putting the empty syringe on the bleed nipple and as you pump the break lever start to pull the syringe creating a vacuum and when you get to the end of the syringe lock the nipple and repeat process, worked on my road bike clutch after i changed a seal in the clutch slave. oh and don't let the master cylinder run empty during the process

Edited May 15, 2010 by steve1979

[tltel]

HI

The way I bleed my back brakes is to use syringe with a small piece of pipe and fit this onto the master cylinder inlet pipe ( remove pipe from reservoir first). open bleed nipple and push new fluid through the system. shut nipple and pump brake pedal a few times still with syringe attached, then remove syringe refit reservoir pipe, top up reservoir,(dont over fill it because fluid needs some space for when it expands) hopefully brakes will be working after that.

Hope this helps

TLTEL

[hoggyf]

Still struggling,

been at it most of the day off and on, couldn't get the pushing method to work at all but it keeps pulling bubbles out by pulling on the syringe then opening the nipple, I get loads of bubbles but can't get any pedal.

I did get the brake to work once but when i test rode it the brake wouldn't lock up even at walking pace, given up for today before the big hammer comes out.

never had this trouble on other bikes or cars, left it all connected up overnight and will give it another try tomorrow.

[jmurray]

http://www.youtube.com/watch?v=FcQq4U5ALyk...player_embedded

[jse]

Still struggling,

been at it most of the day off and on, couldn't get the pushing method to work at all but it keeps pulling bubbles out by pulling on the syringe then opening the nipple, I get loads of bubbles but can't get any pedal.

I did get the brake to work once but when i test rode it the brake wouldn't lock up even at walking pace, given up for today before the big hammer comes out.

never had this trouble on other bikes or cars, left it all connected up overnight and will give it another try tomorrow.

HoggyF,

I understand, back brake bleeding can make you want to resort to handgrenades to "fix" the bike. Sometimes it goes easy with no problems or it can (as you've found out) drive you nuts.

The pressure syringe can help but it does not push much volume so sometimes it does not solve the issue. From what I've found, the main problem with back brakes is an air bubble hiding at the top of the banjo fitting on the master cylinder. If you look at the M/C you'll see what I mean.

This is due to the fact that the outlet is above the inlet for the fluid and higher than the rest of the system. Sometimes (if you can reach it) pressurizing the system and cracking the top fitting on the M/C will work out the air, but if all else fails, you may need to take the M/C off it's mounts and rotate/lower it enough to allow the bubble to be forced out of the fitting area.

Usually, you want to "bench bleed" a M/C by filling it with fluid before installing it, which will help with the bleeding later. If you pull on the syringe, you'll probably only be sucking air past the threads on the caliper bleed nipple (even if you have a bleed hose on the fitting going into a can of fluid), I would avoid that.

Jon

[jonny042]

Still struggling,

been at it most of the day off and on, couldn't get the pushing method to work at all but it keeps pulling bubbles out by pulling on the syringe then opening the nipple, I get loads of bubbles but can't get any pedal.

I did get the brake to work once but when i test rode it the brake wouldn't lock up even at walking pace, given up for today before the big hammer comes out.

never had this trouble on other bikes or cars, left it all connected up overnight and will give it another try tomorrow.

I went through this on Saturday, and I agree with JSE on the root cause of the problem. I was able to "dislodge" this bubble by removing the brake pedal and dust boot, and actuating the master cylinder with a philips screwdriver. With a hose on the bleed nipple, open the nipple half a turn and leave it open, and move the Master cylinder all the way until it bottoms. Do it fast, when I did this it dislodged some pretty big bubbles.

Brake is still not great but it go tme out riding for the day yesterday.

[hoggyf]

This has got to be worse than chinese water torture - arghhhhhhhhhh

I can get a bit of a pedal by syringe back bleeding so you think to yourself I'll give it a couple of pumps on the pedal and build a bit of pressure then bleed of the last of the air - no air comes out and you lose the pedal, it is so frustrating. Gonna remove the master cylinder tomorrow and try to invert it without losing the fluid from the master cylinder. Then again a box of matches might be easier and it'll free up some space in the garage.

[gasser_david]

Hello

I'm no expert - starting again after 7 year layoff - but .......

Essentially,in proocess of "sorting out" 2001 TXT which has also suffered 7 year layof- includes brakes.

Just done front - hope to do rear at weekend.

Used syringe method of "pushing" from bleed nipple up to master cylinder.

To get fluid to flow - trying DOT 5.1 - found that had to open bleed nipple more than anticipated.

This caused fluid to come up thread and leak slightly.

So ...... if sucking not blowing from bleed nipple - would assume that air getting down thread.

As air should move easier than liquid may explain your problem.

FYI front brake was sharp before I started and still is.

Propose to use method for rear as shown on US gasgas site video and if not a success - will try pressurising from bleed nipple with bike front wheel on a beer crate to raise level of master cylinder.

Back brake razor sharp at moment hence still debating as to "leave alone" - only doing it as fluid 2001 vintage - not inspired by your problems.....

david

[hoggyf]

IT now appears to work -

2 man job, one of whom was an enduro and former trials rider (ta very much for the help), what we did was disconnect the supply pipe from the bottom of the reservoir and connect the syringe to that, pressurise the system, then while holding the pedal down, crack the rear banjo, after a couple of goes pedal was firm, disconnect syringe, reconnect reservoir and top up.

Was a bit of a mare as the sysringe wasn't an ideal fit but witha couple of cable ties and holding it in place we got it done, couldn't have done it as a one man job though.

Easy when you know how