no pedal pressure, unless i pump it up?

I have a dilema,
i have no brakes unless i pump the system a couple of times. if i wait about 30 seconds, i have no pressure again.

I have the following: 78 cj5 W/ disc front, drum rear.

i have swapped the proportioning valve, due to a leak, and the master cylinder, both rear slave cylinders, and the calipers on the fronts to try to remedy the problem with the brakes losing pressure.

I have bled the system and have about a gallon of fluid litterally through the system from bleading and bleading. i have the cleanest brake fluid in the world, trust me Please reply?

 

If one of your fittings is loose it will suck air into the system and you can bleed and bleed and never get it. I would suggest you check your fittings for tightness. Did you bench bleed the master, sometimes the air in the valves is the most persistent.

Are your new calipers on the proper side? It easy to flip them leaving the bleeder screw to low to get the air out, make sure the bleeder is at the top. Good luck.

 

Sometimes when you replace the proportioning valve you get alot of air in the system that can be difficult to get out. I have pump bled brakes systems for over an hour with no success and then hooked up a pressure bleeder and got all the air out in less than 5 minutes. And like the previous post stated, make sure the calipers are on the correct sides, the bleeder fittings should point up.

 

I too am having the exact same problem as the OP.

I recently installed a dana 30 from a 79 CJ5 with a disc brake set up.

I suppose I might have installed the calipers on the incorrect sides. I should have the banjo bolts below the bleeder valves when the caliper is properly installed, correct?

Edit : After some reading I found the best approach is to use a MC from a later model CJ with the disc/drums combo and proportioning valve. I noticed however the front and rear outlets for the newer master cylinder are on the opposite side of the master cylinder currently in the jeep. Will I need to replace all the brake lines(not the hoses) to accommodate the new set up?

 

ok, so i power bled the system and now have much better brakes but still have to pump it to get real pressure. I am thinking that bench bleeding the master is next. does anybodt know where to get a kit to do the bench bleed?

 

A lot of replacement master cylinders come with plastic fittings and hoses to use but you can also just buy some steel hard line with fittings that screww into the master cylinder and bend them so they go back into the reservoir under the fluid level. You can do this in the vehichle and have someone pump the pedal and watch for air coming through the lines.

 

Have you adjusted the back brake shoes? If they are having to move too far you will never get a good pedal on the first press.
This is a fairly common problem.