How to bleed rear brakes?

[piorun]

On my latest trip I blew a brake line going to the rear. by the time I got home rear reservior on master cylinder was completly dry. Today I repalced the brake line. When I was trying to bleed them there was no air or fluid coming out. I tried everything I know with no result. How should I bleed those brakes?

[EarlJr]

http://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-69328.html

Suck it back.

[DaveVA78Chieftain]

With the master cylinder (MC) is run dry, the first thing you have to do is bleed the Master cylinder.  Did you bleed it first?

Dave

[piorun]

Yes I bleed master cylinder. I use Mityvac to suck the fluid with no result. There is something like a proportioning valve. I wander if there is some special way to open it.

[Froggy1936]

You have upset the safety valve (the one that turns on the brake light) You will have to open a frt bleeder wile pressing the brake pedal to move it to the other side  Optimal is to catch it in the center then pressure bleed all 4 wheels Must keep MC resivouir topped off  Frank

[piorun]

I will try it tomorrow

[DaveVA78Chieftain]

To ensure we both have the same bleeding concepts in mind:

Manual Brake Bleeding
1. Remove the reserve by applying the brakes several times with the engine off.

2. Fill the master cylinder reservoirs with brake fluid and keep at least one-half full of liquid during the bleeding operation.

3. If the master cylinder is known or suspected to have air in the bore. then it must be bled before any wheel cylinder or caliper in the following manner:
   a. Disconnect the forward (blind end) brake pipe connection at the master cylinder.
   b. Allow brake fluid to fill the master cylinder bore until it begins to flow from the forward pipe connector port.
   c. Connect the forward brake pipe to the master cylinder and tighten.
   d. Depress the brake pedal slowly one time and hold. Loosen the forward brake pipe connection at the master cylinder to purge air from the bore. Tighten the connection and then release the brake pedal slowly. Wait 15 seconds. Repeat the sequence, including the 15 second wait, until all air is removed from the bore. Care must be taken to prevent brake fluid from contacting any painted surface.
   e. After all air has been removed at the forward connection; bleed the master cylinder at the rear (cowl) connection in the same manner as the front in Step 3.d. above.
   f. If it is known that the calipers and wheel cylinders do not contain any air, then it will not be necessary to bleed them.

4. Individual wheel cylinder or calipers are bled only after all air is removed from master cylinder:
   a. Place a proper size box end wrench over the bleeder valve. Attach transparent tube over valve and allow tube to be hand submerged in brake fluid in a transparent container. Depress the brake pedal slowly one time and hold. Loosen the bleeder valve to purge the air from the cylinder. Tighten bleeder screw and slowly release pedal. Wait 15 seconds. Repeat the sequence, including the 15 second wait until all air is removed. It may be necessary to repeat the sequence 10 or more times to remove all the air.

5. It is necessary to bleed all of the wheel cylinders and calipers, the following sequence should be followed:
   l) Right rear wheel cylinder;
   2) Left rear wheel cylinder;
   3) Right front caliper;
   4) Left front caliper.

6. Check the brake pedal for "sponginess" and the brake warning light for indication of unbalanced pressure. Repeat entire bleeding procedure to correct either of these two conditions.

Dave

[DaveVA78Chieftain]

COMBINATION VALVE
The combination valve has two or three sections in it (figure 1). Each section serves a different function.

For front disk/rear drum systems, the metering or hold off section (A) of the combination valve limits pressure to the front brakes until a predetermined input pressure is reached. This should be enough pressure to overcome the rear brake shoe springs. There is no restriction to inlet pressures below 200 kPa (30 psi). This allows for pressure equalization during the no apply periods.

The pressure differential warning switch section (B) constantly compares front and rear brake pressures from the master cylinder.  If the front or rear brake systems malfunction, it energizes the warning lamp on the dash. The switch latches in the "warning" position after a malfunction occurs. The only way to turn the lamp off is to repair the malfunction and apply enough pedal force to develop about 3100 kPa {450 psi) line pressure.

The proportioning section (C) of the combination valve limits pressure to the rear brakes after a predetermined rear input pressure has been reached. This prevents rear wheel lockup on vehicles with light rear wheel loads.

[piorun]

My rig has disk brakes all around. Combination valve looks the same accept it does not have the rubber plug on the left.

[piorun]

Got it done. Bled front brakes to get the combination valve open to the rear than back brakes bled nicely.