problem bleeding back brakes

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plumduster

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still having problems with the 70 duster. installed new disc brake proportioning valve. rebuilt kelsey hayes 4 piston calipers. the problem I had was low brake pedal, so installed new rear wheel cylinders. Cannot get fluid to the back wheel cylinders. fluid does not seem to be going through the proportioning valve. I have been bleeding the brakes with vacuum bleeder, but no fluid. Car was originally drum brakes. Any ideas on what the problem is.
thanks wayne
 
Some of the problems:
Valve is jammed
flares on the lines are incorrect
blocked line
If you had a pedal before and now there is no fluid,its all up front my friend
Take a hammer and tap the valve to see if it unseats,what is the valve off of? New or used? Does it have a sensor in it,?mrmopartech
Call me tommorow at 514 659 0445
 
I'm having the same issue. Replaced everything but the lines and can't get pressure to the rear lines. Fluid does run out of the rear lines but does not spray or squirt out like it's under pressure. Going to try tapping the prop valve see what happens. Any other suggestions?
 
Take the line to the rear brakes loose at the proportioning valve and see if flow freely at that point. If not, it's in the valve, if it flows good, there is a downstream clog somewhere. If the valve isn't badly stuck, sometimes you can free it up by taking the plug out of the end of the housing and tapping on the spool valve inside. If it were me, I'd pull the valve off the car, remove the spool valve, and clean everything up real good before reassembly. don't get carried away sanding the spool or bore as this will ruin the valve. Just enough to get the spool to move freely. That spray brake cleaner works good on deposits that may be inside.
 
I just got finished with a 71 Nova disc brake conversion and had the same issue. I wound up having my buddy pump and hold the pedal and I bled the lines between the M/C and the prop valve, and the outlet fitting to the rear brakes. It took a lot of pumping to clear the air out of the rear lines. My Vacula bleeder was not effective, I think the prop valve limits the flow to the rear brakes quite a bit.
 
66dartman said:
I just got finished with a 71 Nova disc brake conversion and had the same issue. I wound up having my buddy pump and hold the pedal and I bled the lines between the M/C and the prop valve, and the outlet fitting to the rear brakes. It took a lot of pumping to clear the air out of the rear lines. My Vacula bleeder was not effective, I think the prop valve limits the flow to the rear brakes quite a bit.
Click to expand...


X2! I had the exact same issue, all new brake components from front to back to include new lines and proportioning valve. Vaccum bleeder does not work! Need a helper to pump and hold brakes or buy one of these bleeders, it works great!: [ame="http://www.amazon.com/Motive-Products-Custom-Power-Bleeder/dp/B0002KM5M4"]Amazon.com: Motive Products Custom Ford Power Bleeder(0106) Ford 2 Tab: Automotive[/ame]
 
I flat do NOT BELIEVE in "vacuum bleeding." ESPECIALLY in the case of "cups" in drum brakes or hydralic clutch slaves, air can suck past the cup---simply because of it's shape. A cup in a hydraulic slave, or a wheel cylinder, is designed to hold POSITIVE PRESSURE IN (internal pressure), and NOT keep positive pressure OUT (atmospheric pressure), which is what you create when you pull a vacuum.

I also agree --one step at a time.

Stuck proportioning valve, or if you have a "factory" type multi block with warning light switch, it may be stuck or mis - plumbed.

Blow/ flush out the lines. If you blow them out, do NOT use your compressor, which contains moisture. Get something dry, like CO2 or Nitrogen.

Don't be afraid to crack fittings on the way back, such as at the prop. valve/ switch block. You need to be thinking of getting a friend who can pump and hold some pressure at the pedal, or else go to pressure bleeding (pressurize the master)

Make sure the master has not lost prime. It's why you have to "bench bleed" a master.
 
the two person method works best, if you cant find a helper try this
with all bleeders closed, find a length of pipe, 2X4, anything that you can use to press the brake pedal all the way down then wedge between the pedal and the seat or seat frame, with the pedal held in the fully depressed position go around back and open the bleeder, close bleeder remove wedge from pedal and repeat, continue repeating until only clean new brake fluid comes out of the bleeder, dont forget to check and refill the master cylinder every few cycles then go on to the next wheel
 
The valve closed off,did it's job. as the pedal travel was over-pushed. Only push 1/2 way then close bleeder.To re=center- open front bleeder, turn on key, push pedal,watch brake light go off, or feel the click in the pedal. Valve back to center, now will allow fluid to rear/ front again. Don't push pedal past 1/2 way.
 
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