what to do if master cylinder goes dry

Replacing the principal cylinder for your brakes or clutch is a fairly simple chore – unbolt the erstwhile 1, bolt the new one in place, bandy the lines and yous are washed, right? Not exactly. While the actual bandy process is easy, there is one more stride in the middle that yous admittedly must do before you lot accept the new unit to the machine: bench bleed the air out.

What Is A Master Cylinder?

The master cylinder is a hydraulic pump.  Every bit you pump the pedal, it forces the brake fluid into the calipers/bicycle cylinders (or clutch bearing for a clutch master cylinder). This works really well because fluid does non compress. Air, however, compresses quite hands, so whatever air in the braking system volition reduce the hydraulic pressure level by large amounts. Even a single air chimera in the brake line can make stopping your vehicle a scary affair. The primary cylinder does not automatically bleed the air out of the piston when you fill it, this has to be performed "on the demote", in other words, out of the vehicle. Y'all tin bleed information technology in the automobile, but it takes longer and requires two people- ane to watch for bubbling and one to push the brake pedal. Bench bleeding is the best option. If you were to try this with the brake lines fastened, you would push big amounts of air into the brake lines, and it would take a lot of time and effort to remove all of the air from the master cylinder. Yous would stop up fighting spongy brakes for weeks.

Secure the chief cylinder in a bench vise. The bleeder kit installs to the brake line fitting holes.

How To Bench Bleed A Main Cylinder

Bench bleeding is done with the principal cylinder secured in a vice on a workbench. Some new master cylinders come up with a bleeding kit, which consists of two clear flexible tubes, a plastic clip for the lines and ii plugs pins. The lines connect to i end of the plug pins, which are inserted into the restriction fitting holes in the main cylinder. The lines slide into the clip, which secures the lines to the master.

Make sure the lines become to the lesser of the reservoir bowls.

When placing the lines into the bowls of the chief cylinder, brand sure they go to the bottom. Every time you activate the piston, information technology pulls fluid from the bowl and pushes it out the tubes. When the piston is released, it pulls a vacuum on the tubes. If the ends are exposed, they will suck air, negating the work y'all are doing.

Side by side, make full with new fluid.

Fill up the reservoir bowls with fluid. The level volition drop equally you operate the piston. Filling it in one case to total should suffice.

Using a screwdriver or ratchet extension, slowly operate the piston in and out to push fluid through the lines.

Using a screwdriver, or ratchet extension, slowly button the plunger on the back of the principal cylinder in. Make sure it goes all of the mode. Slowly release it, letting it return to the airtight position. The plunger is spring loaded, and then some try is required to move the piston.  Echo this action.

The lines will fill with air and fluid.

As y'all operate the plunger, the tubes will fill with fluid and air bubbling. As you work through the procedure you will see how difficult this would be if the brake lines were attached.

Proceed to operate the plunger until the tubes are free of air bubbles.

Go on to operate the master cylinder until the tubes are gratuitous of bubbles. This can accept five or more minutes. Tap the side of the principal cylinder to assistance and air pockets release from the side of the housing and out the tubes.

Replace the cap onto the unit and plug off the rubber lines. We used a pocket-size bolt.

Once all of the air is out, cap off the lines or if unit had plastic caps, reinstall them into the threads.

Just a couple more than bolts and the master is mounted to the car. Now y'all can attach the brake lines and bleed the main system.

At present you lot can have the new master cylinder to the car and install it. Connect the restriction lines and restriction pedal pushrod. All y'all need to practice now is bleed the residue of the system.

There are chief cylinder units available that take bleeder screws on the torso, which makes the procedure easier, but about factory-style master cylinders do non accept this characteristic. While this is a fairly simple process, it tin exist very frustrating dealing with air bleeding, especially in the primary lines that feed the brakes. If you accept any concerns or can't get the brakes to business firm up, contact your local NAPA AutoCare Eye for help.

Bank check out all the brake system products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more data on what you should know nearly your brakes and principal cylinder, chat with a knowledgeable proficient at your local NAPA Motorcar PARTS store.

Jefferson Bryant View All

A life-long gearhead, Jefferson Bryant spends more time in the store than anywhere else. His career began in the machine audio industry equally a shop manager, somewhen working his way into a position at Rockford Fosgate every bit a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive announcer ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin', Mopar Musculus, and many more. Jefferson has too written 4 books and produced countless videos. Jefferson operates Red Clay Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.

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Source: https://knowhow.napaonline.com/what-you-should-know-about-your-brakes-and-master-cylinder/

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