Is this bad ??

yesterday night I was bleeding 2 rear brake, It was dark that time so im in hurry and forget put the rubber thing that suppot to be on top of the bleeder screw ( is this bad ? ) I went to auto part and non of them carry that black rubber, and by that time I take out the brake calibor the piston that support come out( and I should use the D-clamp to push it back on ) but the piston is still stuck inside ( it support come out when I take out the calibor ) can any one tell me what happent here ( because I missing that black rubber thing cause to the calipor piston not coming out ? )thanks.

the black rubber cap doesnt matter. im not sure what you mean about the piston popping out but still being in :screwy:

yeah dude, i didnt understand one thing that you were trying to say....

PHEW!! it good to hear that black rubber is not important thanks,

you know when ever you take out the brake caliper, to take out the brake pad, after put the pad on , you have to push the piston using the large C-clamp, but my piston already in there , it mean i dont need the C-clamp to push it in, my question is , why the piston doest not coming out?.

I think you worry too much about little things. Be glad you didn't have to push it back in. Sometimes they don't pop out. Did you have trouble stopping before? Put that shit back together and drive man.