scottynz

I have a 2015 Giant Roam 1 with Shimano hydraulic disc brakes (M355). The brakes became spongey after only a few months' use and the front brakes became completely useless. As the Giant store wanted to charge me the same amount for labour to fix it under warranty as a regular bike shop would to do the job, I figured I would just do it myself. I bought a bleed kit from Amazon (one with a syringe to attach to the caliper rather than a cup) and set about doing the job. I succeeded with fixing the brake on the first try. I decided to do the back brake as well, since it was not particularly responsive (though not dead). I ended up rendering it useless! I have now tried 5 times to bleed this brake and nothing! I have tried hanging the bike vertically so that the air moves more easily to the top of the line, but still nothing. One thing I am not sure about is how to secure the bleed hose to the fluid line. The kit comes with cable ties, but there is seemingly no way to attach it with this brake system. I end up having to hold the hose in place at the opening, but this means I cannot put enough force into the syringe to get the fluid moving through the line. If I use both hands on the syringe, the hose pops off and oil goes everywhere (I fear I may have screwed my brake pads now since they are covered in oil). There have been several times though, where I seem to have pushed all the air through the line, nothing has gone wrong, yet still the caliper is as loose as can be and the brakes are completely ineffective.
So, any advice? Any idea what I might be doing wrong? Is there a trick to the back brake that I'm unaware of? Is there any way to clean my brake pads now that they are covered in mineral oil (Riding with just the front brakes is kinda dangerous, since even though they are tight, the oil on the pads makes them less effective... and squeaky!).
Thanks in advance for your help. I'm getting really frustrated with this!

drlogik 

Watch these videos. Explains everything. What it sounds like you aren't doing is purging the air out. Air in the system will give mushy brakes and if too much render them useless. You have to have one end of the system open while you pump fluid into the other end. As you pump fluid in, air and fluid will come out the other end. Once only fluid is coming out you close the bleed port. If the other end isn't open and you put pressure into and against the closed system, the hose will blow off and you won't purge the air and the brakes will be mushy....sounds familiar right?

If you don't have a bleed cup it's not s show-stopper as you just put a rag under the bleed port on the brake lever (or caliper if you are bottom bleeding) and let the fluid spill onto the rag. A bleed cup makes this much easier though. In your case you will probably want to top bleed AND bottom bleed to purge all air bubbles out. For Shimano systems be sure to use MINERAL OIL-based fluid and not DOT fluid. They are completely different and not compatible. Best to buy the Shimano brake fluid.

I started bleeding brakes working on cars at a gas station when I was in high school so this is easy-peasy for me but in general it really is easy once you do it the first time.

One thing neither of these videos tells you to do though is purge air bubbles out of the syringe. To do that, pull fluid in and push fluid out while the end of the syringe or hose is deep into the fluid. Pump in and out slowly until only pure liquid is in the syringe with virtually no bubbles. Even tiny bubbles in a system as small as a bike will make for mushy brakes. As you put the hose onto the bleed nipple also start to pump a little of the fluid out as you attach the hose so that you don't have a bubble at the very beginning.

The best video I have found. It's very good. Watch it straight through at least twice so you remember what steps comes next.

This one is good to:

or this one if you don't have a bleed kit:

gsa103

Try tubing with a slightly smaller inner diameter, it may fit better. Home depot potentially has something suitable.

1) Remove wheel (to prevent oil on the rotor)
2) Remove brake pads (to prevent contaminated pads), and insert the yellow plastic bleed blocks. (Your LBS would probably just give you some if you lost them)
3) Un-bolt the caliper from the frame
Having the caliper free let's you rotate it around to free any trapped air pockets, and generally makes it a much more pleasant experience.

Full Shimano tech docs are here: https://si.shimano.com/#models/1768
Bleeding instructions per Shimano: https://si.shimano.com/php/download.p...006-01-ENG.pdf

In a short answer, no, there is no good way to clean contaminated pads. There are bunch of various home brew methods (automotive brake cleaner, propane torch, etc) sometimes work, do nothing, or utterly destroy the pad, with about equal chance.

Given that the back brake is likely completely full of air (been there done that).
My advice is as follows:
Buy the proper Shimano bleed kit (with funnel) oil, and 2 new sets of brake pads. Then start over from scratch and perform a full top down on the rear.

Chalk it up to a learning expense. The first time I bled Tektro brakes, I flubbed the process pretty badly. Oil everywhere, except the caliper which was full of air.

scottynz

Hey guys, thanks so much for this advice! I will make another attempt in the next couple of days. Regarding the tubing, that's not really the problem. It attaches nice and snugly, but the way the opening is set up, there's nowhere to secure it. The nipple that you attach the tube to is inside a larger 'hole' that's covered with the dust cap. It doesn't protrude, so there is no way to hold it in place other than with your hand. I'm thinking this is not a one-man job, especially if I'm going to need to remove the caliper! That means one person holding up the caliper end of the hose, one holding the tubing in place, and one injecting the fluid!

gsa103

The caliper can just hang down, it's not a big deal.

It sounds like a longer piece of tubing may help, since you should be able to hold the syringe with enough slack in the tubing that if you move the syringe it shouldn't pop off. Or try some more flexible tubing which might fit tighter and flex easier making it more resistant to popping off.

Canker

Put a zip tie around the tube and nipple to help hold the tube on or just gravity bleed the brakes. Shimano are easy. Sram/avid on the other hand you have to sacrifice a chicken to the Gods before you even begin the hard stuff.