No brake fluid coming to the rear

[rickseeman]

Thanks to everyone for the help. The owner is coming tomorrow and we are going to apply the ideas given here. I'm sure it will lead to an answer and then we can fix it. Some things go easier than others. This one wasn't easy for me. Ed: I didn't get any fluid out of the lines when we changed the wheel cylinders. Doug: I think he's bringing new rubber lines with him. By the way MoparLeo, the gentleman that gave me my commercial check ride was a SR-71 pilot. His name was Paul Jones.

 

[Mebsuta]

My money is on the rear brake hose (body to axle). They tend to collapse/plug up with age.

That's exactly what it was for me.

 

[Adam12]

I don't know brakes so I'm going to have to beg for help. This 70 Road Runner hasn't been on the road in many years. We put on a new master cylinder and tried to bleed the brakes. I think the fronts bleed fine but there is no brake fluid going to the rear brakes. We replaced the rear wheel cylinders. I think the power brake booster is out because the brakes feel the same with the motor running or off but that I don't think that's our problem. I'm thinking maybe one of the brass blocks underneath the master cylinder. (Whatever those do.) What do you think the point of failure would be? Surely someone besides me has had this problem trying to wake one up. Thank you.

Did you bleed the master cylinder first?

 

[rickseeman]

Well, thanks to all of you for the help and advise. After I looked at the diagram of the distribution blocks/proportioning valve under the master cylinder and the spool/valves/small passageways in it I thought that must be the problem area. I thought a few of you were crazy when you said the rubber hose. But this morning when we took the rubber hose loose from the rear end nothing came out. Then we took the hose loose from the front and brake fluid pumped out easily. So I kept pumping to get new fluid in the metal lines and flush out the old fluid. I figured if the hose was bad it would leak. How could a rubber brake hose not let 500 psi brake fluid pass through? I don't know and I don't care. We now know that when we put on a new hose we will have fluid to the rear end. Then we will bleed the rear brakes. Our thanks to all of you!!!

 

[Bird 426]

Glad that you found it!

 

[Sixpactogo]

Well, thanks to all of you for the help and advise. After I looked at the diagram of the distribution blocks/proportioning valve under the master cylinder and the spool/valves/small passageways in it I thought that must be the problem area. I thought a few of you were crazy when you said the rubber hose. But this morning when we took the rubber hose loose from the rear end nothing came out. Then we took the hose loose from the front and brake fluid pumped out easily. So I kept pumping to get new fluid in the metal lines and flush out the old fluid. I figured if the hose was bad it would leak. How could a rubber brake hose not let 500 psi brake fluid pass through? I don't know and I don't care. We now know that when we put on a new hose we will have fluid to the rear end. Then we will bleed the rear brakes. Our thanks to all of you!!!

I know you said you don't care but just to let you know what happens with the flexible rubber brake hoses is they have something like 1/32nd orifice in them. After time, they collapse and block the flow. Normally, when they collapse, they will let fluid go through when you step on the brake because it is high pressure but will not let the fluid go back to the Master. People always want to blame the brake cylinder for not releasing when all along it was the hose.
That said, you may want to replace the front wheel hoses too.

 

[rickseeman]

He ordered new front hoses also.

 

[Willislav]

I had the same problem recently on my 70 Charger that had sat for over 20 years. It was the rear flex line.

 

[moparedtn]

Thanks for coming back and letting us know what it turned out to be, Rick.
You'd be surprised how many times folks don't do that and leaves us hanging.

 

[racingjim]

Sometime the rubber hoses get damaged by using a pair of vice grips to pinch the hose so fluid doesn't leak out. That will collapse the hose. Any rust in the system can build up. Whenever I don't get fluid to a bleeder screw (assuming there isn't gunk in the bleeder screw), work your way back to the master cylinder while someone holds their foot on the pedal (loosen the steel fittings at each brake line juncture). At some point the pedal should start to drop. If you get all the way back to the master cylinder, and still no pedal movement with the foot on the pedal, then condemn the master cylinder (in the port within the master there is a residual pressure check valve for all drum brake circuits to prevent air from getting drawn in from the wheel cylinder when you let off the brakes). It could be plugged.
THT