brake problem

[Shields14]

 master cylinder wont pump any fluid to the back brakes  took the line off at the proportion valve and nothing there. no leaks anywhere.  any ideas

[Musicman]

Is this a stand alone adjustable prop valve?
I will assume for the moment that it is not, and that we are talking about a Combination Valve... that said, some of these units, depending on the year and application, have the ability to block fluid flow to the rear brake system if the Hydraulic Safety Switch has been activated. In other words, if you have a problem with the rear brake lines, a substantial leak for instance, the resulting hydraulic pressure differential between the front & rear side of the system will cause a shuttle valve to move toward the rear of the main valve body, activating the brake light switch and blocking fluid flow at the proportioning valve. If this is the case, it must be re-centered.
It could also be the master itself... assuming it's a dual master, have you verified that the master is actually pumping out through the rear line?

[Shields14]

no the master is not pumping out the rear to the m.c

[tan top]

 is it a new master cylinder your fitting ? who it made by ?

[Shields14]

no its the stock 1  77 newyorker.  i took the brake booster off and revamped the rod i am wondering if it just on a bind and not getting deep enough, can someone explain to me how these work if i take the lines off at proportion valve or even the lines off at m.c  and i pump it ,should oil be coming out or does it have to have some kind of back pressure, probably wondering why i got rid of brake booster  lol  the car is a derby car this sight is a awesome place to find out stuff about mopars thats why i asked here, i take the brake booster off so when the car starts to belly it doesnt bend the zoomie pipes. i have built alot of these and never had a issue burt i am right now, i took a couple other m.c and tried pumping them without lines hooked up and they wouldnt do much either 

[ACUDANUT]

Is this a stand alone adjustable prop valve?
I will assume for the moment that it is not, and that we are talking about a Combination Valve... that said, some of these units, depending on the year and application, have the ability to block fluid flow to the rear brake system if the Hydraulic Safety Switch has been activated. In other words, if you have a problem with the rear brake lines, a substantial leak for instance, the resulting hydraulic pressure differential between the front & rear side of the system will cause a shuttle valve to move toward the rear of the main valve body, activating the brake light switch and blocking fluid flow at the proportioning valve. If this is the case, it must be re-centered.
It could also be the master itself... assuming it's a dual master, have you verified that the master is actually pumping out through the rear line?

I ain't buying any of this Switch talk.  It's a combo valve blockage to me. Never seen or heard of a switch that moves brake fluid more or less to the front or rear. 

[tan top]

what i would do , take master cylinder off & bench bleed it  , so you know its working ok ,   if that checks out with out seeing or actually being there  , could be a problem with the  master cylinder push rod  linkage etc  , as the rears are fed by  the front of the master  cylinder

[Musicman]

I ain't buying any of this Switch talk.  It's a combo valve blockage to me. Never seen or heard of a switch that moves brake fluid more or less to the front or rear. 

I don't have the time to explain it all, but this may help you if your actually interested.

http://aero-cruiser.fl-ink.com/tip-run03-a01.htm

A quick quote from the above article;
There are a number of pressure differential switches that perform a second function. In addition to completing the ground to the red warning light, they also shut off the fluid flow to the rear brakes if a rear hydraulic failure has occurred.

[Shields14]

 

what i would do , take master cylinder off & bench bleed it  , so you know its working ok ,   if that checks out with out seeing or actually being there  , could be a problem with the  master cylinder push rod  linkage etc  , as the rears are fed by  the front of the master  cylinder

..  yup bent push rod built a new one and we r good to go. thanks for the help

[tan top]

good you got it sorted 

[ACUDANUT]