piston wont retract!!!

[gonso523]

I have heard it and read it but can't get it. I have replaced my master cylinder, converted to stainless steel lines bought a new piston, piston seal and bleeder. I scraped the hell out of the caliper and my piston won't retract. there has to be one small technique to bleeding the lines or cleaning out the calilper that I am missing. any help would be great.

[TOOLS1]

Use a pump type oil can, and a piece of vacuum hose, to pump the fluid up to the master cylinder from the bleeder. Air wants to go up, not down, and these master cylinders do not move enough fluid to force it down. About your piston not retracting. Is it not releasing from the disc?
TOOLS

[gonso523]

the piston will not release unlease it is hit with a rubber mallet. this oil can thing. are you talking about the speed bleeder kit they sell at harbor frieght or sears or is it something else? where can I get one?

[gonso523]

I just googled it and will pick one up. the other thing I think I am doing wrong is not building up pressure in the line. all I do is fill the line and after there are no bubbles in the line I squeeze the lever and shut the bleeder valve.

[shinyribs]

I just did a caliper today and the piston did not want to move freely in the bore. If installed it would not have retracted either. I sanded the inside of the caliper where the pad rides( Not the piston bore)until it would move freely. A thin coating of silicone grease will help a piston retract down the road. Advance Auto sells a good silicone grease,non-melting,for about $7 a tube. Works good in a lot of other places,too.Handy to have around.

These pistons only retract a very small amount. Any resistance at all will cause it to stick. The rubber piston to caliper seal is what actually causes it to retract. The groove that the seal goes into is machined with a very slight taper that cocks the seal slightly.That cocking causes the seal to "bind" sort of and gives it the ability to retract.Very important that that groove is clean for it to work properly.

Picture=1,000 words

[TOOLS1]

Not a speed bleeder, or a bleeding kit. It's just a simple oil can with a pump. You can get one at any hardware, or auto parts store.
TOOLS