Just replaced my Master Cyclinder and Both Rear Wheel Cylinders. I have good fluid going to the Front Calipers but nothing going to the back wheels at all could it be the proportion Valve???

 

Did you bench bleed the master cylinder before you installed it? Have you been bleeding the rear wheels? Those are loooong lines, if your lines got full of air during the process it can take quite a while to bleed fluid back through them.

 

Just start cracking lines and see if you have fluid. Start at the master and see if fluid drips out.

 

have fluid going all the way to the proportion valve but nothing coming out of the back of it it seems I am wondering if it is the valve because if there are seals in there they might have gotten eaten up due to how bad the brake fluid was. if there are seals in there. I did look at a couple of valves on ebay waiting to hear back to see if they will fit the ford

 

The problem I have run into is rust and sediment. It can be sitting in the system and when you work on it, it gets stirred up and can clog things up.

 

+1 on bench bleeding. It's one of those things that doesn't really seem like it would be required, but it often makes a huge difference. I had previously thought any air will eventually get pushed out when bleeding from the wheels, so why bother bench bleeding the MC? I had a eureka moment over my morning coffee, and I think the secret has to do with the volume of pressurized fluid delivered from the MC.

I think what happens is this: When you push on the pedal while bleeding, any air in the lines obviously gets compressed. However, pushing the pedal only sends a relatively small amount of fresh, bubble-free fluid into the lines. This small volume is not enough to clear the line in one shot. If there was no resistance in the lines, this wouldn't be an issue, as each subsequent bleed cycle would move the air bubbles closer to the bleed screw.

However, add some resistance in the lines, even slight, such as the internal workings of a proportioning valve, and the equation changes dramatically. The air bubble won't pass through the valve. Instead, the air compresses in the line upstream of the valve, and the valve never unseats because the inlet pressure never gets high enough. If you had an unlimited volume of pressurized fluid feeding into the lines, the valve would indeed open once all the air was compressed, but that's not the case. You've only got a limited volume coming from one cycle of the MC, and it's not enough to compress all the air, reach the required pressure (it may not be much), and force its way through the valve.

That's my verbose theory of what is happening and why bench bleeding is so important, even though at first glance it just seems like extra work. Bench bleeding reduces the volume of air present in the lines at the start of bleeding, and helps overcome the volume limitations of manually cycling the MC. It also explains why most shops use a pressure bleeding system, the type that uses a pressurized container feeding through the MC via an adapter in place of the MC cover. That type supplies a essentially limitless supply of pressurized fluid, overcoming the volume limitations of us mere mortals cycling the brake pedal.

My hunch is your proportioning valve is just fine but you've inadvertently introduced air into the upstream lines. Instead of trying to bleed all the way from the wheel cylinders, crack the fitting at the inlet to the valve. Have a helper press and hold the pedal (this will get messy) until you secure that fitting. Release and then hold the pedal down again while you repeat cracking open that fitting. I bet it would only take three or four cycles max to clear any air upstream of the valve. Then the valve should operate normally and you can complete the bleeding process from the rear wheels.

Working from memory here, I think some proportioning valves even had a protruding little pin you held one way or the other with a special clip while bleeding. This held the internal workings open so air bubbles would pass right through. Anybody remember that one, or am I in left field thinking of some other vehicle? I'd get up and dig through my manuals, but the cat is giving me the evil eye for even thinking about stopping scratching her ears.

 

Did you replace the rear brake hose? They can fall apart internally and look fine from the outside. Open the flare nut on the side before the hose see if you have brake fluid there if you can get brake fluid there but not at the wheel cylinder then its probably your brake hose falling apart on the inside created a blockage.

Another thing that can happen is Ive seen hoses fall apart in a way that a flap breaks off and acts as a one way check valve. Brakes will apply but wont release right away.



Also there is a clip to hold the pin out on the prop valve for bleeding. Thing is though Ive never seen this make a bit of difference. Ive even seen holding this pin out and pressing on the pedal will recenter your prop valve so your brake light switch will shut off. Didn't work on my Mercury and not sure if the valve is stuck as can happen if you drive it long enough or if its just the system is not getting equal pressure front and rear.