65 mustang. New booster, master, prop valve (adjustable), metal likes, soft lines, calipers and wheel cylinders.
Pretty much everything in the brakes is out of the box new. Except the springs in the drums.
Anyway, i cant get a pedal.
Fronts are bled well. Solid streams of fluid out the bleeders. No air. But no pressure being developed near as i can tell.
Rear has no fluid movement whatsoever. Cannot get anything going through. Not via gravity, mytivac, or two man. Confirmed clear lines before reassembley, and the master is putting out fluid at the rear line port.
Im stumped.
Ideas?
Any chance you hooked up to the wrong ports on the master? Front circuit goes on the rear ports, usually. This makes a surprising difference to fluid/pressure delivery.
Did you prime/bleed the Master before hooking you lines?
Keith: theyre definitely plumbed properly. Forward resivoir is much smaller and headed to the rear circuit
914: with the way this thing goes together, there was no way to. So we filled the master. Crack like at master, pump pedal to floor, close line. Repeat a lot.
Did you go step by step to the rears? Pressure from the master cylinder (check), pressure out of the proportioning valve, pressure to the T at the rear axle etc? I always treat these like you would an electrical issue............start at the beginning and keep going down the line till you find the point of failure.
The other thing that comes to mind, is the pedal/master cylinder fully releasing? I had a similar issue on the Datsun once and figured out the master cylinder wasn't fully returning that last 1-2mm.
I've uses two methods for new systems:
1. Back bleed the system. I've got an old pump can I use..........crack the bleeder, pump, close bleeder, repeat.
2. The method I learned via Carrol Smiths Tune/Prepare to Win books; lines from the bleeders to jars/can of brake fluid. Pump the pedal (air gets pushed out fluid sucked in) until you no longer get any air bubbles in the jar. This method works really well when you don't have a helper.
Adjust the rear shoes all the way to the drums. The wheel cylinders are just growing and shrinking.
If you can't get anything out of the front port( the one that goes to the rear) you may have the front piston stuck down a dry bore a bit, covering the transfer port. Take the front line off, tap the front end of the cylinder and maybe it will pop back. Also, check pushrod length and make sure there is a wee bit of free play.
Next time, don't push the pedal down so far. I never push the pedal any more than it would normally travel. Also, bench bleed the master, so you don't have to shove all that extra air all the way to the back of the car.
Is the prop valve adjusted to closed?
Keep it coming! Gonna try it ALL after work
Had two tings like this on my 1969 Cougar brake bleed issues earlier this year.
1)Is the splitter on the rear axle leaking or plugged up. Mine was a PITA to get sealed up for some reason
2) Soft pedal in my case was solved when I adjusted the back shoes out to the drum surface
I installed new shoes and cleaned and greased the adjuster the cranked it in when installing the hardware. Angry suggested I look at that as my issue and tweaking them brought the shoes out to the drum and gave me a good pedal. Your case may be worse if the car has 4 wheel drums. I converted to front disks so I had good braking action but a weeny pedal. That fixed it.
Robbie
MegaDork
3/20/20 4:27 p.m.
L5wolvesf said:
Is the prop valve adjusted to closed?
Totes. I had this exact issue duster on the Skylark I did last year. There is a spring loaded failover in the prop valve on dual circuit cars that can shut one circuit if there is a large pressure differential.
I needed to take the valve apart to reset it.
Find the root cause? Inquiring minds want to know.
Its in the prop valve. Teardown is happening now.
Glad you found the problem.
How about swarf left in there? Sonofa.....
In reply to Dusterbd13-michael :
Too many bad new parts. They're everywhere
Yup. Sad thing is that i have had the EXACT SAME PROBLEM with two other adjustable prop valves before. I should have preemptively disassembled this one...
