calipers rubbing and no pressure in lever - disc brake

Mrtennis

So I installed my new (second hand but new to me) juicy ultimate rear brake today and it's not working right.
There is no pressure in the lever. You can pull it back to the handlebar with hardly any resistance whatsoever. This put a slight braking force on the rotor but hardly anything. The when I release the lever, as there in no pressure in it, it doesn't spring back like it should. The calipers then retract a bit but are still clamped to the rotor and they rub. The wheel will still spin but obviously stops extremely quickly.
I am guessing the no pressure in the lever is because they probably need bleeding? How about the calipers no retracting to their original position? I have experimented and take the wheel off, pushed the pads back and then the wheel spins perfectly. The I press the leaver, with the rubbish non-existant pressure and the pads don't go back out to where they started.
So is it just a matter of bleeding them? Or do I need to clean the pistons?
I have built my bike and I mostly understand how disc brakes work but these are my first set. If I take the pistons out to clean them will the fluid just pour out? I don't have any DOT fluid yet to fill them back up so just want to know that if I go and take it apart this evening, if that's what it needs, will fluid be going everywhere and they won't be up and running until I fill them again?

supersonic

Clean pistons, and bleed.

You'll need the proper bleed kit, available on ebay cheaply.

Mrtennis

Thought so.
Also, having never had these, or any disc brakes before, there is something I'm not sure about. From the lever's resting position (not squeezed) I am able to push against the back of the it in the direction of the front of the bike. It then flicks forwards, like it's on a latch. Is it meant to do that? It doesn't seem to be a problem but as I said they are second hand and having never used any disc brakes before I don't know if this is normal, for this specific model or any disc brake.

mattv

Where did you get the brake from? I have seen avid brakes do this in the workshop a few times, with no real explanation or fix. A clean up and bleed helps, but never gets them perfect. Avid brakes are very powerful and very light, but their quality control is dire.

Chunkers1980

Should have bought some new m596s

Mrtennis

mattv wrote:

Where did you get the brake from? I have seen avid brakes do this in the workshop a few times, with no real explanation or fix. A clean up and bleed helps, but never gets them perfect. Avid brakes are very powerful and very light, but their quality control is dire.

Bought them off ebay . With all due respect, after doign a load of research before buying any disc brake, there were scare stories and positive stories for every brake out there. If anything the scare stories seemed to be in the minority with these brakes.
The guy I bought them off said they had been lying around for a couple of years but were still working. So I suppose the fact that they've been lying around, many people would say they should be bled etc. Which makes sense. On the other hand my bro has some juicy 5's on his bike which he hasn't had to touch since he bought the bike about 6 years ago. He has talked me through much of the rest of my build as he knows about bikes. The one thing he doesn't know anything about though is hydro discs as he's never had to do anything to his!