Dreaded Combo/Prop Valve Issue

[3404bbl]

I put a combo prop/metering valve, similar to the one SixPak posted below, on my 63 Dart. I've got an issue with the front brakes. If I pump them up, I can hold them all day long. If I let off 1/2 or even 3/4 pedal, I still have good brakes. But, when I let all the way off the pedal, the next push goes all the way to the floor. Pump two or three times and they're solid as a rock. Master Cylinder is good. I used the plugs that came with the M/C and isolated the issue to the front. With the back M/C reservoir plugged off and the back brakes plumbed in, it's solid as a rock. WIth the front reservoir plugged off and the front lines plumbed in, the problem is consistent.

My question is in regards to the metering valve. Is there something funky with them, that would cause the problem? I was at a car show this weekend and there were a lot of street rods with similar combo valves, with one of the ports to the front brakes plugged off, and the other port going to a splitter that fed both sides. 99% of the street rods did it this way. I saw at least 15 cars with one port blocked off, and only one car using both front ports. Does anyone think if I changed mine to plug off one of the front ports and use a splitter off the other, it might help my problem?

[bOb shingler]

i don't even use one of those. did you bleed the brakes?

[farmington]

If your pedal feels good sometimes and then goes to the floor its the master cylinder thats bad.  the combi valve is nothing but a distribution block with a pressure switch inside that connects to the brake light on the dash.  My duster sat without brake lines for 20 years.  After I put a new m/c and brake lines I couldn't get any fluid to the rears.  the fronts bled fine.  I took out the plug that covers the pressure switch and it was all cruddy, cleaned it up, replaced everything, and voila, then I could get fluid to the rears and they bled just fine, thank you.   Check that.  There's nothing but that inside of the combi valve.

[3404bbl]

through, just fluid. I'll try cleaning the pressure switch.

[signet]

there may be a need for a residual pressure valve if that combination valve is for a disc set-up.

[Jim_Lusk]

That's not an a-body valve, but that shouldn't matter. You might to replace the front brake hoses as they may be balooning.

[qkcuda]

I read somewhere that certain bleeding methods won't work properly with a combination valve.  I'm thinking there is a problem if you vacuum bleed them, but you can pressure bleed them?  Can anybody clear this up, since I will be doing mine this winter?

[redfastback]

gravity bleed it first to see if fluid is getting there.  open 1 bleeder at a time and wait for fluid to starting coming out.  no need for special bleeding.  after that do the old fashioned method of one on the pedal and one at the brakes bleeding them.  jim did bring up a good point about the front hoses though.  you may have a bad master.  how did they bleed at the front?  good?

[joesnow]

Don't count out a bad master. I have had a simailer problem on a none mopar. Bad Mastercylinder.

[NYrr496]

Sounds like a bad master to me more than anything.

[acpat]

  master