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The brake master cylinder is a key component of a vehicle's brake system. If this component fails, then your vehicle's braking ability will be weakened or destroyed. To avoid this safety hazard, it is best to replace the brake master cylinder. The following is a guide on how to replace a brake master cylinder.

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  1. 1

    Locate the various components of the vehicle's brake system. [1]

    • Use your vehicle's manual to identify these components.
    • Locate the brake fluid reservoir, the brake master cylinder, the brake fluid level sensor, and the brake fluid lines.
    • The brake fluid reservoir is usually at the top of the brake system and contains brake fluid. It can be identified by the presence of a threaded cap on top of it.
    • The brake master cylinder is typically located directly beneath the brake fluid reservoir.

  2. 2

    Remove the brake fluid from the brake fluid reservoir.

    • Remove the cap.
    • Use a siphon or turkey baster to remove the brake fluid.
    • Dispose of or recycle the brake fluid in accordance with local laws and regulations. Contact your local agency that deals with household hazardous wastes for any needed information.[2]

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  3. 3

    Remove the brake fluid sensor connector. [3]

    • This is part of the brake fluid level sensor that you previously identified from your vehicle's manual.
    • This can often be removed by pulling it with your hand.
    • Follow the instructions in your vehicle's manual.

  4. 4

    Remove the brake fluid lines.

    • Loosen the brake fluid lines with a line wrench.
    • Twist the line wrench in a counter-clockwise motion on each brake fluid line until all of them have been removed.
    • Keep a towel or cloth handy to clean up any brake fluid that leaks as a result of this procedure.

  5. 5

    Detach the brake master cylinder. [4]

    • Use a socket wrench to remove the mounting bolts from the brake master cylinder. These bolts can be located in your vehicle's manual.
    • Remove the brake master cylinder by hand.

  6. 6

    Install the new brake master cylinder. [5]

    • Put the new brake master cylinder in place of the old cylinder.
    • Connect the mounting bolts with a socket wrench.
    • Tighten to prescribed torque or at least as tight as the old ones were.
    • Fill the fluid reservoir with fluid allowing some to run out the brake pipe holes.
    • Get somebody to gently pump the brakes while holding a container under the holes.
    • This "primes" the cylinder and purges excess air.
    • Reconnect the brake fluid lines by turning a line wrench clockwise.
    • Reconnect the brake fluid sensor according to the instructions in the vehicle's manual.
    • Use the type of brake fluid that is listed on the cap or in your vehicle's manual.
    • Bleed the new brake master cylinder.
    • Optional - remove front wheel from furthest hub. Push brake cylinder back.
    • Optional - remove other front wheel. Push brake cylinder back.
    • Optional - If you do this watch for reservoir overflow, catch as required.
    • Optional - This effects a "reverse bleed" that releases some air close to the master cylinder.
    • Optional - pump brake pedal to return cylinders, top up fluid as required.
    • These optional steps make the subsequent bleeding much easier because the air is close to the master cylinder.
    • Check pedal free play. If there is an adjuster on pedal adjust to take up slack BUT do not allow no free play. Brakes will bind.
    • Brakes must be bled after master cylinder replacement.
    • Purchase a bleeder kit from an automotive supply store.
    • Follow the directions that come with the kit.

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Add New Question

  • Question

    After bleeding my brakes, the pedal is not having pressure, what should I do?

    wikiHow Staff Editor

    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

    wikiHow Staff Editor

    wikiHow Staff Editor

    Staff Answer

  • Question

    What do I need to do to a master cylinder before installing it on a car?

    Community Answer

    The new master comes with two clear rubber hoses and two plastic nipples that screw into the holes where you would put the brake lines. Screw and tighten the nipples. Fill the master cylinder with fluid. Put one rubber hose in each chamber of the master, and then connect them to the nipples. You need to place the master in a vise, in the round part in the back of cylinder between the two holes where it bolts on. Use a Phillips screwdriver and pump it -- it will be really hard to push, but push until you no longer see bubbles in the clear hoses. Make sure the hoses stay in the fluid -- you may need to have someone hold them while you pump.

  • Question

    What is wrong with my brakes if the brake light is on?

    Community Answer

    If you put you foot behind the brake pedal and pull up and the light goes off, look up in the pedal and see if the electrical switch is loose or broken. If not, you need to have your breaks checked by a mechanic. Make sure it's not your ABS light.

  • Question

    Should I take out the master cylinder after bleeding the brakes?

    R-Dixie- Normus

    R-Dixie- Normus

    Community Answer

    It doesn't matter, because you're still going to have to bleed them when you replace the master cylinder. Once the lines are disconnected, you've let air into your brake system. Air in the brake system is not good as it can seize up the brakes. Make sure you bleed the brakes AFTER you install the new master cylinder, though.

  • Question

    How do I remove air from the clutch slave cylinder?

    Community Answer

    One way is called gravity bleeding: loosen the bleeder on the slave cylinder, making sure the fluid is full. Open bleeder until fluid gets low in the reservoir. Keep filling it up with the bleeder open and the cap off the reservoir.

  • Question

    How difficult is it to replace the front brake shoes and master cylinder on a 2005 Camry if I have little auto knowledge?

    R-Dixie- Normus

    R-Dixie- Normus

    Community Answer

    It is not very hard. If you're able to locate a few bolts, and piece a puzzle together, changing brake shoes is a piece of cake just as much as the master cylinder. The only challenge for a newbie would be using the tools that are required.

  • Question

    I had my master cylinder replaced, but my brake pedal keeps going down. What is wrong?

    Community Answer

    Try rebleeding the complete brake system, brand new fluid! Be certain you are using the correct "dot" type brake fluid. If once completed the same symptoms occur, you may have a seepage or leak in the system or even a faulty master. Or you may have to power bleed your system. Also be sure the master is not a stage 4 type as this kind requires a special bleeding technique. Be sure your power brake booster tank and fittings are not leaking out or within.

  • Question

    How do I adjust a clutch master cylinder?

    Community Answer

    Drain and clean it then refill with new clutch fluid. Bleed the cylinder like brakes and check for a stiffer pedal. If still not fully disengaging, look under dash board at the clutch pedal that nothing is restricting the full travel (carpet or floot mat).

  • Question

    How can I replace the master cylinder on a 1949 style line Chevy Deluxe?

    Community Answer

    Use plenty of releasing fluid on all attached fittings daily for a week. Carefully release fittings a little at a time. A tight nut can be freed by heating the nut very carefully and rubbing a wax candle on exposed threads. Try again. If the nut moves a few threads, wind back and try the candle trick again so more wax wicks further along the threads. When all attachments are undone, remove the unit. I don't know if that model used cable brakes, so doublecheck.

  • Question

    How do I remove the brake reservoir?

    Community Answer

    Pull it up with your hands, it pops out. Be careful not to get fluid in your eyes.

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  • If you are uncertain as to whether or not the brake master cylinder must be replaced, check it for fluid leaks. A fluid leak indicates that it must be replaced immediately.

  • Brake bleeding is a two person process. Don't even bother until you have a friend.

  • Bleed the front wheels first. See how it goes - you may not have to bleed all four wheels.

  • Master cylinders should generally be replaced rather than repaired.

  • Check all 4 wheels for fluid leaks.

  • A low brake pedal indicates a potential problem with the brake master cylinder. If you push the pedal and it goes further to the floor than usual, inspect the brake master cylinder for damage immediately before driving again.

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  • If you opt to take the vehicle to an auto mechanic instead of fixing it yourself, exercise caution by driving slowly and allowing plenty of room between your vehicle and other vehicles. Have the vehicle towed if the vehicle's braking ability has been severely reduced or if it no longer works at all.

  • Test the brakes before driving in traffic. Press and hold the pedal down. It should stay solid. Confirm that the brakes can hold the car - easy with an auto - put the car in drive and with the brake on apply a bit of gas. Car should not move. At your first opportunity, while driving at around 30 km/h (19 mph), check the rear view mirror, if clear, then apply the brakes quite firmly.

  • Do not attempt this if you are a novice or "first timer". Even a small mistake can prove deadly to yourself and others. This is one of the most vital parts of the car. If you are not 100% confident, take it to a shop!

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