I can't bleed my bleedin' brakes. (Shimano SLX 2012)

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I can't bleed my bleedin' brakes. (Shimano SLX 2012)

30 posts & 12 voices | Started 7 months ago by Brown | Latest reply from ampthill

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Brown - Member

I'm trying to bleed my 2012 SLX brakes and I'm failing. They keep pumping up noticably.

I'm fine bleeding most brakes - old shimano, older shimano, formula, magura - no problems. But can I bleed these? Not a chance.

I've followed the instructions to the letter, four times. I've checked the system multiple times and I'm fairly certain (99%) there are no leaks. I've got to the stage (several times) where I can't get any more bubbles of air out, and yet they still pump up.

So. There's clearly either:
a) still air in there (and idea where or how to get it out?).
b) Or someone has fiendishly emptied my mineral oil and replaced it with something else. (Could anything have happened to the oil? I didn't think it could absorb water or anything like that.)
c) Or I'm just being a total muppet.

Any ideas?

Posted 7 months ago #
Brown - Member

Anyone? They're doing my head in!

Posted 7 months ago #
tony24 - Member

Just bled my xt's have you got the funnel ? What process are you using?

Posted 7 months ago #
neilsonwheels - Member

It's because its 2011 try again in a few months.

Posted 7 months ago #
Brown - Member

Using a syringe instead of a funnel. But it probably is because I'm a few months too early.

Posted 7 months ago #
cruzheckler - Member

how can you do it WITHOUT the funnel?

Posted 7 months ago #
bryan-g- - Member

If they are like the XT ones I have I pushed the fluid from the caliper up wth a syringe, that did the job.

Posted 7 months ago #
DickBarton - Member

Have you tried moving the calipers? Might be trapped in the body so move it so the air shifts...

Posted 7 months ago #
tony24 - Member

I cannot see how you can bleed them without the funnel. You have to pull as well as push so it cant be done.

Posted 7 months ago #
cruzheckler - Member

If you bleed without the funnel all you are doing is pushing air into the reservoir

Posted 7 months ago #
DickBarton - Member

Can you reverse bleed? From calipers up...

They still use mineral oil? Have you used dot fluid instead?

Posted 7 months ago #
Brown - Member

I'm using half a syringe on a hose, screwed into the reservoir. It's basically a funnel. Or is there something magical about the funnel that I haven't realised?

I've reverse bled them, on and off the bike, shaken them. sworn at them, slapped them about and I still can't seem to get all the air out. Does it get trapped anywhere in particular?

I think I might be getting somewhere by dangling them underneath the bike, letting the pistons come out and then pushing them back in again. I can only think I have air trapped in the caliper somewhere, somehow.

Posted 7 months ago #
Brown - Member

Scratch all that. I've found the problem. A piston seal was leaking.

Posted 7 months ago #
mart - Member

Apart from your bleed nightmare, how do rate the brake, assuming you've had some trouble free use of them? What's the smallest rotor you reckon you can get away with for UK trail centre use?

Posted 7 months ago #
Brown - Member

Pretty good really. Rotor-wise, I had 160 on the back and 180 on the front and that was plenty for general riding and playing in Wharncliffe. For more XC use I'd have 160 front and back happily as there's plenty of power. I like the slightly squidy feel you get from shimano brakes so they're good for me in that way and they've been pretty consistant in use really.

That said, my 2004/5 XT rear has now gone back on, having outlasted two sets of servo wave Shimanos...

Posted 7 months ago #
PJay - Member

I thought that you were meant to bleed with a syringe from the bottom up. The funnel screws on to remove the need to take off the resevoir cap.

This is an M575 bleed video but I think the technique is the same.

It won't help if you have a leaky seal though, I didn't spot that

Posted 7 months ago #
chilli - Member

I had the same issue and it was the same problem, since found out it's a common fault, replaced seal,cleaned em up, sold on ebay for £115!!! bought some nice formulas instead.Sorted.

Posted 7 months ago #
pete68 - Member

Right, I need to bleed my 2012 cya after making a hash of shortening the hose. Where do you get a suitable syringe from? I can't seem to find a shimano syringe online and nothing came with the brakes. I do have the little yellow funnel.

Posted 7 months ago #
DickBarton - Member

Got to a local vets...I got a small supply from them, think they charged me a princely sum of 50p! I explained what it was for and they didn't seem that fussed...

Posted 7 months ago #
dave_aber - Member

If you bleed without the funnel all you are doing is pushing air into the reservoir

Is that not the point of bleeding? Move the air from where you don't want it to where you do want it?

Posted 7 months ago #
cruzheckler - Member

why would you want air in the reservoir??

Posted 7 months ago #
DickBarton - Member

Because you can then remove it very easily...by adding more fluid (which then removes/replaces the air)...but if the air is in the hose or stuck in the caliper then it won't be replaced...

Posted 7 months ago #
dave_aber - Member

^ wot he said.

Posted 7 months ago #
cruzheckler - Member

but how would you add oil with no yellow funnel - this is where this came from btw

Posted 7 months ago #
DickBarton - Member

A syringe? I don't know...I don't know how the brake works for bleeding...never seen one...but I'm guessing if a funnel can be fed into the reservoir then a syringe can go likewise (and assuming the nose of the syringe is smaller than the funnel), then air should escape more easily as it will escape via the gap between nose and reservoir.

Posted 7 months ago #
cruzheckler - Member

not able to comment then dick as it was specific question

Posted 7 months ago #
DickBarton - Member

Of course I can comment...it's bleeding a bike hydraulic brake system...however the funnel gets fitted, the 'hole' will be pointing upwards (otherwise the fluid will drain out)...so instead of sticking a funnel in there, use a syringe...and just dribble the fluid in...any air that remains in the reservoir will then work it's way to the bleed hole and will therefore escape...

Just checked a picture of a 2012 SLX brake lever...appears to be a rather standard looking setup for the reservoir so the syringe will work fine for ensuring the last of the air has been removed from the reservoir.

Are you asking about a funnel because the instructions say you need a funnel or have you got a wealth of brake bleeding experience and knowledge that means a funnel is the best solution?

Posted 7 months ago #
cruzheckler - Member

both

Posted 7 months ago #
dave_aber - Member

Shimano's Words

Looking at the Shimano bleeding guide, it is pretty comprehensive. It's basically a back-bleed using a syringe into an upper catch tank (the "funnel"), followed by a gravity bleed into a bag, followed by a 'conventional' pressure bleed of the caliper using the lever/master as the pressure source, followed by a final reverse gravity bleed of the reservoir, and a neat clean removal of the catch tank.

You can do all of this without the funnel, but it won't be as clean.

In most hydraulic breaking systems it isn't so important to get all of the air out of the reservoir - every road car / road motorbike reservoir has air in it (at the top). For this application though, where excessive vibration could lead to any air in teh reservoir getting mixed with the fluid, then introduced into the pressure line it is desirable to get all of the air out eventually during the bleed.

You could do all of this with just a large syringe though, and some rags to clean up any overspill.

Posted 7 months ago #
ampthill - Member

book marked to help me find those instructions....

Posted 7 months ago #

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