[Trep01]

Hello, I've spent some time researching this topic throughout the forum and have read through my manual but I just can't figure out why I can't bleed my brakes. I bench bled the MC and had my brother pump the brakes while I loosened the "bleeder". Nothing comes out. No fluid and no air. I even bought a brake bleeding vacuum tool and nothing flows through the lines to the rear drums. Any words of wisdom? Thank.

[dave-r]

More info required.

These questions are to get an idea of the state of your master cylinder.

How did you bench bleed the master cylinder?
Did you hook two lines from the output ports back into the reservoirs?
Did you get good flow of fluid through the cylinder? Did you push the piston the full length to get out all the air?

Next questions.

When you open the bleeder and push down on the brake pedal do you;

Have a firm pedal or does it easily go all the way to the floor?
Do you hear any air pushing out of the bleeder?
Does the fluid level in the master cylinder move at all?

[Trep01]

Thanks dave.....I bench bled as you described. The bleeding kit came with the MC and I bled with the tubes in the kit and by pushing the piston all the way in (about 8 times). The fluid flowed over well. I'm not hearing any air come out of the bleeder and the fluid isn't going down at all. I tried to bleed the rear wheels yesterday and wasn't able to get either wheel bled.

The pedal is firm and when the bleeder is opened, doesn't go down to the floor. As we pump it it does firm up and then when we open the bleeder, nothing happens.

Thanks again.

[Adrian Worman]

On 72 on cars, maybe others I ain't really sure, don't they have a brake pressure warning switch on a valve just under the m/cyl? Mine has, I had to thoroughly clean it when I last did a fluid change.
That can be checked to see if fluid is reaching that union just by loosening it, at least you know you got a blockage some where, maybe in that valve
At least crack the union to it anyway, if you can see any traces of fluid, you can rule out a m/cyl issue then too.

[burdar]

You shouldn't have a firm pedal if the lines are full of air. It sounds like you have a blockage somewhere. Make sure your getting fluid to the prop valve. If you are, then make sure you're getting fluid through the valve. My guess is you have a problem with the prop valve.

Once you can confirm you have fluid flow through the prop valve, just open all the bleeders. Let gravity moved the fluid for you. Some people have said it took an hour for fluid to get to all the wheels. I got fluid to all wheels in 10 minutes by just having the bleeders open. Then bleed the brakes starting at the right rear wheel and ending at the left front wheel.

[dave-r]

Have you tried opening the bleep valves on all four wheels?

The flexy hoses can collapse internally causing a blockage too. But it would be unusual to happen on all three at the same time.

[Trep01]

Thanks to all of you for your help. I figured it out......don't try to bleed your brakes with the battery disconnected. I connected the battery and the fluid started to flow. Yes, I feel like a fool.

Thanks again.

[dave-r]

Battery?

The battery has nothing to do with the braking system. You got me confused now.

[RedRaven]

Hey Trep,
Hey fire away with the questions and listen to these guys they know their stuff....

Dave,
Now there are two of us Trep and me to VEX the bejasus out of you lol.

[Trep01]

Dave, I really have no idea......believe me. I enlisted the help of my brother and he noticed that the valve below the MC (proportion valve?) had an electrical lead coming out of it. He thought that maybe the value was closed because the battery was disconnected and at that point I was ready to try anything. I hooked the battery cable to the battery and on the first try we had success. I know, it makes no sense to me either. However, the fact that the fluid started to flow was enough to bring credibility to his suggestion.

Coincidence? No doubt.....but whatever the reason.....I now have brakes.

Thank you again.

Trep

[dave-r]

That wire is just for a warning light. The valve is a safety switch. If you lost brake pressure to one end of the car there is a little piston in that valve that moves and switches the brake warning light on. That is all the wire is for. But the piston also prevents you loosing all your fluid by blocking off the side with no pressure.

However it probably was that switch blocking the flow anyway if the valve and lines were completely dry of fluid.

For example. If you were trying to bleed the one wheel all the time the valve may have moved to seal that end of the car.

If a system is completely empty of brake fluid (such as when fitted with new brake lines) I always gravity bleed the system initially. Just crack open all four bleed screws and wait until I see fluid at a wheel before closing it.
Only then do I get a buddy (usually my wife) to pump the pedal so I can check at each wheel for any air bubbles.