Fill the reservoir about halfway...
Fill the reservoir about halfway with brake fluid and pump up the pressure while observing the gauge. Open brake bleeders one at a time like you would with someone pumping the brakes. Pump up the pressure as it falls off.
Open the bleeder and have a helper slowly depress the brake pedal about halfway. You will get a lot of air bubbles until there's solid fluid flow. Be patient and wait it out. Keep the master cylinder filled with fluid and continue the bleeding process. Again, slow pedal depression (halfway) until all the air bubbles are gone. Do this with each brake until there's solid fluid flow.
Negative Pressure Method
When you don't have a brake-pedal helper, it's nice to know there are alternatives that enable you to bleed brakes all by yourself. Mark Jeffrey of Trans Am Racing showed us a homemade negative pressure brake bleeder he created using easily obtained parts. He demonstrated his self-bleeder with exceptional results by removing all contaminated fluid and air from our '67 Mustang's braking system.
The Eastwood Company offers a couple of brake-bleeding kits. Most popular is the single-handed brake bleeder known as the MITYVAC. Instead of relying on master cylinder pressure, it draws brake fluid from the caliper or wheel cylinder, which removes air and contaminants into the small MITYVAC chamber. With each stroke, it removes 1 ci of brake fluid and air, enabling you to bleed brakes by yourself.
This is the Power Bleeder...
This is the Power Bleeder from The Eastwood Company. Fasten the head on top of your Mustang's master cylinder, add brake fluid to the master cylinder and reservoir, and pump up the pressure.
While cruising through Eastwood's catalog, we discovered another approach to brake bleeding, one that involves applying pressure at the master cylinder without pumping the brakes. The Motive Products Power Bleeder from The Eastwood Company involves pressure application and administering brake fluid at the master cylinder. Pump up the pressure and crack the bleeders. It's like having someone's foot on the brake pedal.
Bench bleeding a master cylinder fills the bore with fluid and removes all the air. Here's how to bench bleed with the master cylinder on your Mustang. Whenever you bleed brakes, always make sure your helper doesn't press the pedal too far. Push the pedal all the way to the floor and you can shove the master cylinder piston too far, wedging it deep in the bore and rendering it useless. The pedal needs to be depressed just enough to move fluid and remove air without jamming the piston.
Also be aware of power brake booster preload. Excess preload moves the master cylinder piston into the bore, cutting off fluid supply. Make sure the piston is at rest before beginning brake bleeding.
Power brake booster preload...
Power brake booster preload is an important issue. The power booster rod is adjustable and should just touch the master cylinder piston without moving it. Preload the master cylinder piston and it will be impossible to bleed the brakes.
New master cylinders come...
New master cylinders come with a handy brake bleeding kit. Fill the reservoirs and slowly pump the pedal halfway. Watch for bubbles. When they stop, you've bled the master. Install the lines and don't spill DOT 3 or 4 brake fluid on your paint; it can cause damage.