I have a 2002 civic and the drum brake wheel cylinder piston keeps on popping out. I bleed the brake and it’s find. But as soon as I turn the car on and step on the brake I lose pressure and it pops out. Mind you i went through 2 bottle of brake fluid to make sure all the bubble were out. I need help. I was think the brake booster or master cylinder but I have no idea

 

How tightly does the drum fit over the shoes?

 

It’s pretty snug and I forgot to mention I changed the hardware and brake pad at the end of the summer

 

Looks almost like it’s too short. Have you compared the wheel cylinder length between that and the other side?

 

No that I think of it I have not

 

Was the drum on and over the studs before you bled the system?

Also, check the other side as the wheel cylinder may go into the shoe recess, the shoes need to be raised.