Rear cylinders still leaking after replacing them

the wheel cyliners need to be replaced ,that is most likely where it is leaking , recommend bleeding the brake system both front and rear after changing the rear wheel cylinders

Did you get a good bleed with fluid coming out at all four wheels? If they bled good, and the pedal still goes to the floor, you need to check the brake master cylinder-it is probably shot with an internal leak. An internal leak will not let fluid pressure build up, so no brakes.

Did you keep the brake fluid reservoir from going dry while bleeding? If it went real low, air might have got back into the lines.

It is not uncommon when bleeding brakes on an older vehicle for the master cylinder to suddenly develop an internal leak and require replacement . Here's why: pushing the pedal all the way to the floor causes the master's piston to push in farther than ever before. The rubber cups then travel over a section of the cylinder not usually touched by the cups-old fluid can develop a crud there and when the piston pushes over it, the cups can get ruined. To avoid this when bleeding brakes, put a short piece of 2X4 wood block under the pedal. Then the pedal will not extend the master's piston beyond it's normal travel. Of course on a new master cylinder, you do not have to do this. A new master cylinder does require bench bleeding before installing, however, to ensure no air pockets develop from there.

Put a new copper washer under the flex hose
to caliper where it leaks

There is no bleeding the master,just do the system
at all four corners

Make sure you bleed from rear furtherist from master cylinder and make sure when your helper is in drivers seat to pump brake pedal 4x then hold, at that holding point you open bleed screw then close once brake pedal is on the ground. Repeat 5x then move to the opp side and do the same. Then to the front furtherist from master cylinder and do the same. Making sure the brake fluid is always topped up also. Also check all your conecters in the lines are not leaking

you need to bleed your master cylinder also. you are going to need help pumping on the brakes. and you can bleed your brakes on the master cylinder lines just you bleed your brakes.

You probably need to start over...1st by bench bleeding the master cylinder...(you can do this on your truck...review the bleeding instructions...after completing this you need to be sure the master cylinder is full of brake fluid...you will need a helper...but your next step will be to bleed each wheel brake caliper or cylinder. Start with the right rear, next left rear, then right front to drivers side front...(farthest away to start) you may have a brake fluid leak...if not, your pedal pressure should continually raise...Hope this helps.

Did the pedal go to the floor beforehand? Was the master cylinder leaking, and did you bleed it properly? If the master cylinder was not leaking, check your brake lines going to the rear wheels.

Hi, the problem is usually the brake wheel cylinder inside. Put the car in park but do not set the brake. Jack up the wheel and remove the wheel and drum. At the top of the hub assembly you will see a cylinder between the tops of the shoes with rubber boots on each side. If fluid leaks out when you pull back the edge of either boot, the cylinder is leaking and must be replaced.
Purchase a new cylinder and also some brake fluid if you don't have any on hand. Check your reservoir. Hopefully it is not empty, or you would have drawn air into the system. Fill up the reservoir before replacing the wheel cylinder.
To replace, use a vice grip plier to remove the return spring that holds the shoe tops together, then pull the shoe tops away from the cylinder. Place something under the hub to catch the fluid that will leak during the replacement.
Loosen the hydraulic fitting on the back of the hub using a line wrench of the correct size, then remove the 2 bolts holding the cylinder to the hub (see picture below). Have the new cylinder handy and disconnect the line from the old cylinder. Quickly remove the old cylinder and put in the new one. Screw the line fitting on finger tight and then replace the bolts. Replace the return spring between the shoes. Tighten the line and open the bleeder valve above the fitting about one turn. The line may gravity bleed the air out. Give it a few minutes. If clear fluid starts to leak out and no bubbles, tighten the bleeder and reassemble the wheel. If it does not gravity bleed, replace the drum and have someone assist with a pressure bleed. With the bleeder closed, have the assistant pump the brake pedal and then hold it down while you open and close the bleeder. They should not let up on the pedal until you have closed the bleeder. repeat this process of ejecting air and fluid until only fluid comes out. Then replace the wheel and let the car down.
Please let me know if you have any questions, and thanks for using FixYa.

First do you have ABS next did you bench bleed the new master cylinder if not you can;t bleed the rest of the system You have to keep in mind that you have opened the entire system up and there is going to be a lot of air traped in it Getting back to the master cylinder it needs to be bleed pirior to installing it you need a little kit put the fittings into the holes where the lines go put the little hoses in to the resivoior put the cylinder in a vice and push on the pistion from the back until no more comes out of corse you need to fill it first then install it and rebleed the lines starting at the ferthise cylinder away from the master and work to the closest and its going to talk at least 10 to 15 pumps for the rears less for the front becase there closer and there is less line to bleed Make sure you have no leaks first if you see anything at all stop and fix the leak Hopefuly don;t have abs thats a whole differant thing but the brake still work fine with out it get them working and worry about that later good luck

several thing came cause this. \
1). rear section of the masker brake cylinder has air.
2). break or leak in the brake line
3). brake cylinder (piston) boot leaked.

have some one help you to bleed the brake.
let me konw if you need instruction on bleeding the brakes.