Another "brake help" thread...
I'm thinking
Give the pedal a hit to turn the light on, then back off the pedal and wait.
When you lift, the fluid should return to the master. and the springs inside the C-valve should center the shuttle valve, thus turning the light off. Give it a few seconds.
If this happens as above then;
First of all, the fact that the light turns on and off indicates that the C-valve is in fact working!
Secondly, Ima thinking;
one of two things is wrong,
1) one side of the master is not pumping fluid, or
2) one side of your system from the C-valve onward, has excessive fluid-travel.
I'm going with Option #2.
Here is a cutaway to help you envision how the M/C works.
In this image, the ports labeled "inlet" serve double-duty as compensating ports.
Notice that the "piston" on the right is NOT connected to the piston on the left.
The two pistons are supposed to be hydraulically coupled by brake fluid in that left chamber. Bench bleeding is essentially designed to fill that chamber.
Notice that the piston on the right has a stub-shaft integrated to the front of it. If the chamber is not filled , then that stub moves to the left and pushes that left side piston by mechanical action. This takes extra pedal travel.
The left side piston activates the rear brakes. If the shoes are not adjusted up tight, then that piston will have extra travel. Notice where the "inlet port" to that front chamber is.
If you make multiple stabs on the pedal, each time the power piston returns, more fluid will enter the chamber, and eventually, there will be enough fluid in the system to activate the rear brakes.
But, when you release the pedal, and wait, the shoe return springs in the rear brakes, will pull the shoes back onto the anchor, which will force all that fluid, back into the reservoir. and so, the next time you apply the brakes, you're back to multiple pumps.
I think, this situation can only exist if
a) that interchamber is devoid of fluid, or
b) the front brakes have excessive air in them.
As you can see, that inter-chamber can get fluid from both ends. So then, as long as the power-piston is returning fully toward the right, fluid will enter it. And whenever the power-piston travels past the "inlet port" on the left, fluid will again enter the port.
But look closely
If the left piston passes the port, there is nothing to keep the fluid in the inter-chamber from rushing out into the front reservoir.... which would allow the right-side piston to move forward and go into mechanical mode. Instantly, there would be a pressure differential in the lines and the "combination valve" would turn on the light.
Therefore, the key here, IMO, is to readjust the rear brake shoes to limit the wc piston travel. But of course, this also means to eliminate air in the lines, which is what the C-clamp system is designed to discover.
All that to say, what others have implied, is that your rear shoes HAVE to, at rest, be sitting on the top anchor-post, which means that the Parking cable must be fully relaxed.
Good luck
I'm thinking
Give the pedal a hit to turn the light on, then back off the pedal and wait.
When you lift, the fluid should return to the master. and the springs inside the C-valve should center the shuttle valve, thus turning the light off. Give it a few seconds.
If this happens as above then;
First of all, the fact that the light turns on and off indicates that the C-valve is in fact working!
Secondly, Ima thinking;
one of two things is wrong,
1) one side of the master is not pumping fluid, or
2) one side of your system from the C-valve onward, has excessive fluid-travel.
I'm going with Option #2.
Here is a cutaway to help you envision how the M/C works.
In this image, the ports labeled "inlet" serve double-duty as compensating ports.
Notice that the "piston" on the right is NOT connected to the piston on the left.
The two pistons are supposed to be hydraulically coupled by brake fluid in that left chamber. Bench bleeding is essentially designed to fill that chamber.
Notice that the piston on the right has a stub-shaft integrated to the front of it. If the chamber is not filled , then that stub moves to the left and pushes that left side piston by mechanical action. This takes extra pedal travel.
The left side piston activates the rear brakes. If the shoes are not adjusted up tight, then that piston will have extra travel. Notice where the "inlet port" to that front chamber is.
If you make multiple stabs on the pedal, each time the power piston returns, more fluid will enter the chamber, and eventually, there will be enough fluid in the system to activate the rear brakes.
But, when you release the pedal, and wait, the shoe return springs in the rear brakes, will pull the shoes back onto the anchor, which will force all that fluid, back into the reservoir. and so, the next time you apply the brakes, you're back to multiple pumps.
I think, this situation can only exist if
a) that interchamber is devoid of fluid, or
b) the front brakes have excessive air in them.
As you can see, that inter-chamber can get fluid from both ends. So then, as long as the power-piston is returning fully toward the right, fluid will enter it. And whenever the power-piston travels past the "inlet port" on the left, fluid will again enter the port.
But look closely
If the left piston passes the port, there is nothing to keep the fluid in the inter-chamber from rushing out into the front reservoir.... which would allow the right-side piston to move forward and go into mechanical mode. Instantly, there would be a pressure differential in the lines and the "combination valve" would turn on the light.
Therefore, the key here, IMO, is to readjust the rear brake shoes to limit the wc piston travel. But of course, this also means to eliminate air in the lines, which is what the C-clamp system is designed to discover.
All that to say, what others have implied, is that your rear shoes HAVE to, at rest, be sitting on the top anchor-post, which means that the Parking cable must be fully relaxed.
Good luck