Issue with rear hydraulic brake.

[Sqealybrakes]

Hello all,

My uncle advised me to come ask this here.

Bought a mountain bike the other day, not got a lot of experience but have been tinkering.

My main issue is the back brake.

It's a Shimano deore br-m595 https://i.imgur.com/ssHMepY.png

From what iv read it's a great brake. There was no resistance to the brake lever. I checked the pads and they seemed fine.

So I bought a kit, topped up the oil and bled my brakes. It wasnt straight forward and the one video I could find of this brake system getting done, that way did not work.

I have the little funnel that screws in. But that does not fit. It's a reservoir (see pic - https://i.imgur.com/YHfrMRI.png)

It was entirely dry. So I topped it up with liquid. And then went about bleeding. So I attached a tube to the bleed nipple and just into a bag to contain the liquid.

I pumped the brake 3 times. Held it on. And then quickly opened and closed the bleed valve. This got most of the old fluid out. But the reservoir was not going down like the guy in the video said it should. It just remained full until I could get no more old mineral oil out the system.

So. I problem solved. I attached a syringe to the bleed nipple ensuring no air was in the tube or the syringe. I also made sure the reservoir was open, but full. I then opened the bleed valve and pushed oil up through the system until the reservoir overflowed a little bit. I did this a few times until no bubbles came out.

I sealed the system and the brake was firm. Not as firm as I would like. But 1000% better than it had been.

However the back brake is still not great. It slows you down. But it just does not have the bite of my front brake.

It also sings. Makes that horrible squealing noise.

So I took the wheel off and cleaned the disk, both sides with isopropyl alcohol and ensured it was nice, shiny, clean and bone dry.

The issue still persists.

So I took the brake pads out and took them to the sander and just roughed them up a little bit.

Still the issue persists.

I have ordered new pads which will arrive in a couple days.

But does anyone else have any experience or expertise they could shine on this.

I'm completely out of ideas and any help would be greatly appreciated.

Thanks in advance.

[mattsccm]

You are doing the rights things regarding the squeal.Check all is tight as well. As for the bleeding, well every brake is different so I can't help there but it looks as if the rear still has a touch of air in it.

[AndyA]

It sounds to me like you've got a leaky caliper. The brake fluid has to have gone somewhere when it leaked and it sounds like it's gone on your pads/rotor causing it to squeal. One way to check is to clean the caliper as best as you can, let it dry then put some tissue paper behind the pads, squeeze the lever hard repeatedly with a rotor or spacer between the pads. if the tissue paper is wet, you've got a fluid leak. With Shimano the easiest course of action is fit a new caliper, they're not expensive and come with new pads. There are basically 2 types, one that connects hose to caliper with a banjo bolt, and one that connects with a sleeve nut. If you've got the sleeve nut type you'll also need an olive and barb

[Brucey]

if the squealing only started after your bleeding antics, I'd suspect that you just spilt some fluid that contaminated the pads perhaps. If the squealing is an older problem it could indeed be a leaky caliper and new pads will only provide a temporary solution.

FWIW the bleeding process can be imperfect if the hose is awkwardly routed; eg when bleeding rear brakes it seems to help all the air to escape if the hose is routed uphill all the way from the caliper to the master cylinder. This often means that it goes better if the bike is tilted in a workstand or the front wheel is placed on a step or something.

cheers

[Sqealybrakes]

You are doing the rights things regarding the squeal.Check all is tight as well. As for the bleeding, well every brake is different so I can't help there but it looks as if the rear still has a touch of air in it.

Thanks for your reply. I think there is a bit of air in the system. As for the squealing. I think it may be a leaky caliper.

[Sqealybrakes]

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[Sqealybrakes]

if the squealing only started after your bleeding antics, I'd suspect that you just spilt some fluid that contaminated the pads perhaps. If the squealing is an older problem it could indeed be a leaky caliper and new pads will only provide a temporary solution.

FWIW the bleeding process can be imperfect if the hose is awkwardly routed; eg when bleeding rear brakes it seems to help all the air to escape if the hose is routed uphill all the way from the caliper to the master cylinder. This often means that it goes better if the bike is tilted in a workstand or the front wheel is placed on a step or something.

cheers

The squealing was there before I bled the brakes. And it's continued after, and after everything I have tried to clean the pads/rotor. From what iv seen it unfortunately looks like a leaky caliper. Which i didn't even think think of. I'm gonna strip the whole brake off the bike. Fit a spacer and do as you advised with the paper towel. And see if there is any leak.

Thanks a lot for your advice, it's given me soemthing to move forward on.