bleeding rear brakes

[Barrabob]

okay i have bleed plenty of brakes before but usually i dont let air in them in the first place so dont need to bleed them later just top them up.

went in for a set of rear pads at a shop and the kid cracked the bleed nipple without presure on the system i asume to push the piston in and i got back brake with no peddle.

Been pumping and bleeding for a bit but still no peddle and i havnt seen any bubblles coming up the bleed line either.

take it back in the morning hope i dont get any funny stories.

any ideas like undo the banjo at the slave and bleed there and then move down the line??

Really shouldnt be this hard.

Usually if theres air you can pump it till it goes hard then when you realease it looses presure then you can pump it up hard again.

[I-K]

went in for a set of rear pads at a shop and the kid cracked the bleed nipple without presure on the system i asume to push the piston in

If he really did that, he needs a crack himself, as in across the head.

What happened to the big flatblade screwdriver between the old pads and twist?

any ideas like undo the banjo at the slave and bleed there and then move down the line??

Prezactly. I've never done a brakeline or a master cylinder swap where I didn't have to crack the banjos at some stage. Air gets trapped somewhere between the bolt and the inner surface of the banjo chamber such that pressure in the system just pins it in place instead of flushing it upwards.

Solution, squeeze the lever, crack the banjo, let some fluid ooze out, then whack it back up tight and continue bleeding as normal. If still no go after a while, do the other banjo.

The main suspect usually seems to be the banjo at the master cylinder end.

Whenever I do this, I strip every shred of bodywork off the bike and park it in the opposite corner of the shed, under plastic, and I drape a wet cloth over the lower portion of the affected rim.

[Yankee]

I am doing a brake change this w/e and this little post has helped out all ready!!
Cheers Bob and Ick!!
I remember letting a bit of the brake fluid dribbling onto my 1st bike back in the day.... surely the stuff isn't THAT corrosive.... w/in the hour I needed a new side fairing!! So that wet rag trick is a good idea for the rim....
I knew of the big screw driver trick (you sorta figure those types of things out for yourself), but wasn't aware of the banjo culprit....

Long winded cheers!

[mike-s]

using a g clamp you can compress a piston gently and as long as you've got the cap off the reserviour and a syringe to drain any extra fluid out, you dont need to go ANYWHERE near the bleed nipple. Also if the guy has fudged it this badly another thought is to push the piston in totally and drain the system and start from scratch to make sure it's bled properly.

oh and agreed about the bodywork. at the least i put a torn up garbage bag, covered in a wet towel if i dont remove the bodywork in the general area. does the job usually

[mitch179]

IK is on the money, when i did the fronts on my bike (twice, once when i broke the brake res the other when fitting braided lines) i had to crack the banjo at the MC cause it gets an air lock, and if u dont get it out .. then good luck pumping away til your hand falls off

and im with IK on giving that dude a crack for opening the bleed nipple to start with!

[Ben]

get a clear bit of tube(1m clear), place it over the nipple, pump the brakes as normaly, and as you go to unscrew the nipple suck on the tube, make sure the resevoir is full and when you stop getting air bubbles hold the pressure and lock it up. Repeat till good, any questions pm me
hth cheers

[javaman]

Things could be hard when air gets in AND would not go away with normal bleeding procedure.

In this case I would get a 1m clear tube, put it on the nipple and SUCK the bastard (loosen the nipple first of course).

Once done proceed with normal bleeding procedure

[Barrabob]

will give the suck and spit technique a go.

a old mechanic taught me that if you just crack the bleed nipple and keep pouring fluid into the master cylinder you will have clean fluid and no need to bleed it just gravitys through.

this sucker i poured half a bottle of brake fluid through last night and it still wont pump up but by that stage the knurling on the brake pedel had taken a toll on my hand from all the pumping and bleeding so i will get back to it when i have time.

[Gosling1]

.....The main suspect usually seems to be the banjo at the master cylinder end.

always and forever has this been the *best* place to bleed any brake system.

Think about air bubbles trapped in a tube........where do they normally go ??? well, ya cannae change the laws of physics...........air bubbles *rise* .....they do not go seeking a bleed nipple that is way down the end of the forks......

On the old bikes I work on, bodywork is not an issue, but tanks are, so use a nice fat towel around the m/c to soak up any excees fluid......and beware, once you build up pressure in the m/c, it only takes a *little* squeeze on the lever to have brake fluid going *everywhere* -

Rear brakes are no different - the highest spot in the system is *generally* the banjo bolt under the rear m/c........

Tip # 69 - Its Not So Bad To Have Air In The Rear Brake Line.....

Especially if you have a braided steel line - otherwise you get a brake *switch* not a progressive *brake*............

[I-K]

I forget where I saw it (the Products section of a Pom bike mag, most likely), but there's a braking kit out there with a bleed nipple on the master cylinder banjo bolt... which also doubles as a pressure sensor you can use as a takeoof to work the brakelight on your special or to provide telemetry on your racebike.

Now that's clever.

[Yankee]

I "flushed" a bottle of brake fluid through my two front lines tonight when replacing the pads. The glass I was using to catch the "excrement" from the clear tube started off black and slowly turned to the clear yellow of the new fluid. Never let the level go below the low line, and I now have AWESOME brakes!! couldn't have been easier!