The Stovebolt Site Forums The Shop Area General Truck Talk Front brakes won't bleed.

This is my first time ever installing a brake system. I’ve got a '50 3100. I converted the front brakes to the disc set up from CPP. Added the dual master cylinder with no power under the floorboard. Stayed with the original Huck brakes on the rear. Both the rear brakes were rebuilt. I have the master cylinder plumbed thru a combination valve and installed a 2 lb residual valve on the front to prevent backflow. I installed all new lines and fittings. I bench bled the master and installed in the truck. The rear brakes bled fine and pumped right up. The front disc brakes are another story. When bleeding I can get little or no pressure out of either caliper. I Bench bled the master again just to make sure. Next I plugged the outlet ports on the master cylinder and checked the pedal. Pedal was solid so master cylinder is fine. I plugged just the front & tested rears. Great pedal, no problems there. Connected to just the fronts and pedal goes to the floor. Installed a couple of speed bleeders. Can get weak fluid pressure out of right side and nothing on left. I removed the left side brake line and get some fluid out. Reinstalled line. Tried bleeding again and nothing on left side. Started at the master and cracked fittings and can get fluid pressure right to right side caliper. Still nothing out the bleeder on left. Cannot find any leaks or blockages. What am I missing here?

Hy jss1956, it sounds like you have done everything correctly, did you plumb the discs to the primary side of the master cylinder [the side closest to the pushrod]? Try completely removing the bleed screw from the left caliper and see if you can get anything out of it, your caliper may be faulty, or possibly a plugged flex line to the left caliper. Let us know what you find.

By the pushrod I'm assuming that you are referring to the front of the cylinder where the brake lever (pedal) connects. Here is a link to a pic http://i157.photobucket.com/albums/t72/jss1956/DSCN1530.jpg . The connection on the left is going to the front brakes. You can see the blue residual valve on the left. The port on the right is feeding the rear brakes. From your description do I have this backwards?

Hy jss1956, if the master cylinder was for a disc/disc system the reservoirs should be the same size so capacity should not matter, however most vehicles with disc/drum brakes have the front [disc] brakes plumbed into the primary side of a dual master cylinder. Does your combination valve still have the ability to shuttle over and seal off a leaking system, or has it had the valve locked into position? If it is not locked in position, it may have shuttled over to seal off the front brake system during the bleeding process [the system with no pressure while bleeding]. There were some tools made to lock the valve in position while bleeding. If your valve still has its electrical connection and it is a one terminal setup, check for continuity between the terminal and the body of the valve, if it is a two terminal type, check for continuity between the two terminals. If you get continuity on either of those checks, then the valve has shuttled over, and must be recentered before you can get much if any fluid through the sealed off system. To do this you must open the rear system while generating a pressure in the front system, you may have to plug the port right at the combination valve to accomplish this. Gently bring up the pressure and check for continuity, when the continuity goes away the valve is in the center. I would try and purchase the locking tool for your valve and keep it in place until all brakes are bled. I would also suggest that you plumb the front brakes into the primary reservoir, hope that helps.

If the portioning valve is from CPP you can disconnect the rear brake line from the proportioning valve and manually reset the slide valve using a small screw driver. CPP has a write-up on their site how to do this. They also sell a plug to replace the sensor switch on the proportioning valve when bleeding, to prevent this from happening, cost is about $10.

You would think they would just include it in the kit (like an alignment tool when you buy a clutch and pressure plate).