Hi I am new here and was hoping someone could help me out? I recently had to replace the Master Brake cylinder, all slave cylinders and the brake switch on my 79' Series III SWB because it was leaking. After I fitted all the parts, and bleed the brakes, I tried to apply the brakes and the pedal would loose pressure and go to the floor, only after a few pumps of the brake pedal will it return to normal operation. After driving a while the same thing happens when I apply the brakes. I've tried different bleeding of the brakes and my mechanic even tried to pump out the system but the same thing happens, any ideas? Thanks for any advice.

 

Did you prime the master cylinder with new fluid before you installed it?
Mike

 

Hi Disco Mike, yes I did, I do however notice that there a slight seepage of brake fluid from the new brake switch, could it be the brake pressure distribution valve? I can't see anything else I could have done wrong?

 

That seepage could allow air into the brake lines.
Mike

 

ok cheers, I guess I'll try replacing the valve.

 

I dont have any exp. with the 79 III but I had a similar problem on my Porsche. The switch would be the number one guess for me. Any seepage in the brake system is unacceptable, point blank, period.Its practically the one thing on therover that shouldnt leak.

 

thing is the switch is brand new, and I had to order everything with great difficulty because I am overseas. My truck's been off the road since January.

 

Just about anywhere where brake fluid will get out, air will get in - as has been said above, fix all apparent leaks, rebleed the system on all four corners and try it again.

One thing the series brakes are prone to and if it does this while stationary then this will not apply to your situation, if the drums aren't properly round (you'll need to check them with a micrometer or caliper to be sure, even if they look round) the pistons get pushed back into the cylinder as the drum rotates, forcing fluid back into the reservoir. Depending on how ou of true the drum is depends on how far the piston gets pushed back in - but it has a similar feel to air in the lines and can mean the pedal will drop almost to the floor on the first press of the pedal - pumping the brakes brings the pistons back out and normal braking is resumed.

Hope that helps,

 

I was told I can remove the shuttle valve entire, and fit two unions to join the piping, minus the valve. That way the two sections are still seperate.
anyone here can confirm this? I have 2 inlet pipes and 3 outlets from the shuttle valve, has anyone done this here before? thanks