First off - This is my first time posting so Thanks in advance forany help. (ltrftp)
here goes,
I was changing my rear pads out for the first time myself- had a friend helping
So I pop the caliper off the mount, pads come loose, piston is still pressurized.

New pads are thick, so I need to push the piston in. so I pry it in with the old pads and a screwdriver. It pushes in as normal with resistance.
Only now I have no pressure all of a sudden. When I pump the piston out, it doesn't stay. if it doesn't suck back in on its own, its easily pushed in with 1 finger.. so I check for leaks, can't find anything but a little moisture on the hose under the conduit, but no apparent leak.

So even though I didn't open the system, I thought maybe it was air. So I held in a pump and let the relief valve loose and re-tightened.

Is the next step completely bleeding and replacing the brake fluid? or, is it likely I busted a seal when I pushed the piston in?

obviously, I had pressure at first, having to pry in the piston, which makes me believe whatever the problem is, it started with pushing in the piston.

Any suggestions, before I bend over for the dealer and say ok.?

 

I don't understand what you are trying to say? When you pump it it doesn't stay out but then it doesn't go back in on its own? Where is it then? The pistons aren't supposed to go in on their own, i don't think ever. Some have springs on the side to press the pads apart but that's it usually the movement of the rotor will push them apart enough.

so whats your problem exactly? Take some pictures maybe it will clarify

 

the piston has no pressure. (ie. won't stay out). But like I said this wasn't a problem until i pushed the *functioning* piston in to put new pads on.
i don't know how else to explain it. I guess i could snap a pic of the piston...... but theres no leak around it or anything.........


???

 

Is there air in the system?

So there is no pressure when you push down on the petal. Is the petal getting stuck in down position when you remove the little spring? And when you pull it up is there pressure?

If you pull it up and there is a little pressure its probably your master cylinder seal is busted.
if not it could be just air in your system

 

did you pump the pedal many times or just 1 time? you need to pump the **** many times.

 

Had the same problem when i changed my brake pads too. You have air in the line from when you had to loosen the bolt to release the pressureso you couldpush the cylinder in. Go buy a bottle of brake fluid, and pump the **** out of the brake while the little bolt with the rubber cover cap is tightened. Pumpthe hell out of the brake, and then hold itdown firmly. If you have a friend to help, have themloosen that little bolt quickly, and quickly tighten it back. ( YOU KEEP HOLDING THE BRAKE DOWN ALL THE WAY ORAIR WILL GET SUCKED RIGHT BACK INTO THE LINE)
It will spray out some brake fluid, somake sure it doesnt go in your eyes.Repeat that step several times, and make sure you dont run out of brake fluid while doing it.It doesn't hold much brake fluid, so after 2 or 3 times of pumping it and letting the pressure out of the line, you will probably have to fillit back up with brake fluid. Just make sure you keep holding the brake down firmly each time you release the pressure out of the line. Dont let off the brake until the bolt has been retightened.

A friend of mine taught mea little trick a long time ago while changing the brakes on my car that made bleeding the air out of the line a lot easier. Get a rubber hose/tube that fits snug over the little "nipple" thats under theblack cap.Like one of those littleblack rubber air lines you see under the hood of cars. Anyway, get a full bottle of brake fluid, loosen the brake fluid bolt, the slip one end of the hose over the nipple thingie, and put the other end of the hose into a bottle of brake fluid. And simply start pumping the brake slowly. The air in the line will be pushed out, and when you let up on the brake lever, brake fluid gets sucked back into the line instead of air.. It works great on cars. I'm sure it would work the same for a bike.

 

If you want to spend some money you can buy a decent handheld vacuum pump and its a 1 man job after that. From experience, the bleeder screw doesn't need to be loosened very much at all. It will easily suck air in around the threads. I put some teflon tape around the threads to prevent air getting in. Vacuum pumps also keep brake fluid from getting all over your bike, floor, face, etc.

 

Why do the seals take up so much volume space in the resovoir it makes things messy . Also I didn`t ride the bike before I changed my pads how gripy should the brakes be . I`m thinking I have air because the front and back don`t really stop the bike very quickly .

 

The bike should stop faster than it can acclerate.

 

thanks for the input - solid help.

I guess I did have air in the line, because i pumped my heart out last night for close to an hour, and it finally seemed to start working properly and bleeding w/no air / pressurizing.

I did notice at one point that when the piston did come out, and stayed pressurized, it looked like it was coming out crooked.. so i tapped it until it straightened out withthe butt-end of a screwdriver. as soon as it straightened out, it easily pushed in (still had air in the sys at this point). so that was akward, coming out crooked and all. - i assume that happened because of prying the piston in at a bad angle.


now as soon as i get my $8 mounting bolt from the dealer (because my Friend snapped mine) I can hope everything falls into place.