Brake Master Cylinder

Remove and replace the brake master cylinder, including bleeding the brake system to restore proper hydraulic brake function.

Warnings

Tools required

Parts

• Brake master cylinder × 1 — Use OEM Honda part number
• Master cylinder O-rings/seals × 1 — Often included with master cylinder
• Brake line copper washers × 4 — Use OEM specification

Fluids

• DOT 3 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level surface, apply parking brake, and place wheel chocks behind rear wheels
2. Ensure engine is cold before beginning work
3. Disconnect negative battery cable to prevent inadvertent airbag deployment while working near steering column
4. Place protective coverings over front fenders to prevent paint damage from brake fluid spills
5. Remove engine cover if equipped (pulls up from grommets)
6. Open hood and identify master cylinder location on driver side firewall
7. Have at least 1 quart of fresh DOT 3 brake fluid ready and unopened until needed

Procedure

1. 1

   Remove brake fluid from reservoir
   Using a turkey baster or fluid transfer pump, remove as much brake fluid as possible from the master cylinder reservoir. Transfer old fluid to a suitable waste container. This minimizes spillage during removal. Note: Brake fluid is hazardous waste and must be disposed of properly.
2. 2

   Disconnect brake lines from master cylinder
   Working from underneath the master cylinder, identify the two brake line fittings. Using a 10mm flare nut wrench (six-point), carefully loosen both brake line fittings at the master cylinder. Have shop rags ready to catch dripping fluid. Once loosened, unscrew fittings by hand and position brake lines away from work area. Cap or plug open brake lines immediately to prevent fluid loss and contamination.
   ⚠Use only a flare nut wrench to prevent rounding off brake line fittings. Rounded fittings may require brake line replacement.
   Torque spec

   Brake Line Fittings15 Nm (11 lb-ft)
3. 3

   Disconnect electrical connector
   Locate the brake fluid level sensor electrical connector on the side of the reservoir. Press the locking tab and carefully disconnect the connector. Position it away from the work area.
4. 4

   Access master cylinder mounting nuts from inside cabin
   From inside the vehicle driver footwell, locate the brake pedal assembly. Look up toward the firewall to find the master cylinder pushrod connection to the brake pedal. You will see two mounting nuts securing the master cylinder to the firewall from inside the cabin. Note the orientation of the pushrod connection.
5. 5

   Remove master cylinder mounting nuts
   Using a 12mm socket and ratchet from inside the cabin, remove the two nuts securing the master cylinder to the brake booster/firewall. Support the master cylinder from the engine bay side to prevent it from falling once the nuts are removed. Keep track of any spacers or washers on the studs.
   ⚠Master cylinder will be free to move once nuts are removed. Have an assistant support it from engine bay or support it yourself before removing second nut.
6. 6

   Remove master cylinder assembly
   From the engine bay, carefully pull the master cylinder straight out from the brake booster. The pushrod will disengage from the booster as you pull. Remove the reservoir cap and pour remaining fluid into waste container. Inspect the rubber grommet/seal where the master cylinder mates to the brake booster for damage.
7. 7

   Prepare new master cylinder
   Remove new master cylinder from packaging. Verify it matches the old unit exactly (reservoir orientation, mounting studs, port locations). Install new O-ring or seal onto the master cylinder nose that mates with the brake booster. Lightly lubricate the O-ring with clean brake fluid. Check that mounting studs are clean and threads are undamaged.
8. 8

   Bench bleed new master cylinder
   Fill the new master cylinder reservoir with fresh DOT 3 brake fluid to the MAX line. Install bleeder fittings or thread the old brake lines loosely into the ports (if using old lines, ensure ends are clean). Position master cylinder in a vise or have assistant hold it level. Using a clean dowel or blunt rod, slowly push the master cylinder piston in and out repeatedly. Watch for air bubbles coming from the ports into the reservoir. Continue until no air bubbles appear (typically 10-20 strokes). Keep reservoir filled during this process. Remove bleeder fittings/lines and plug ports with clean fingers until installation.
   ℹ️Bench bleeding removes most air from the master cylinder before installation, making system bleeding much easier.
9. 9

   Install master cylinder to brake booster
   From the engine bay, carefully align the master cylinder with the brake booster studs and pushrod. Push the master cylinder straight onto the booster, ensuring the pushrod seats properly and the O-ring seals correctly. The mounting studs should protrude through the firewall into the cabin. Have assistant verify studs are visible from inside cabin.
10. 10

    Install and torque mounting nuts
    From inside the cabin, install the two master cylinder mounting nuts onto the studs by hand. Install any spacers or washers in their original positions. Using a torque wrench, tighten the nuts evenly in a cross pattern to the specified torque. Verify the master cylinder is seated flush against the brake booster from the engine bay side.
    ⚠Multiple torque specifications exist in database (25 Nm and 26 Nm). Verify correct specification in Honda service manual for your specific model year before final torque.
    Torque spec

    Master Cylinder Nuts25 Nm (18 lb-ft)
11. 11

    Connect brake lines to master cylinder
    Install new copper crush washers onto the brake line fittings. Thread each brake line fitting into the master cylinder ports by hand to avoid cross-threading. Once hand-tight, use the 10mm flare nut wrench and torque wrench to tighten the fittings to specification. Verify there are no gaps between fittings and master cylinder body.
    ⚠Two different torque specs exist in database (15 Nm and 19 Nm). Verify correct specification in Honda service manual before torquing. Do not overtighten as this can damage fittings and cause leaks.
    Torque spec

    Brake Line Fittings15 Nm (11 lb-ft)
12. 12

    Reconnect electrical connector and fill reservoir
    Reconnect the brake fluid level sensor electrical connector until it clicks into place. Open a fresh bottle of DOT 3 brake fluid and fill the master cylinder reservoir to the MAX line. Install the reservoir cap hand-tight.
13. 13

    Bleed brake system - Rear passenger wheel
    Start with the wheel farthest from the master cylinder (rear passenger). Remove wheel using proper jack and jack stand procedures. Locate the brake caliper bleeder screw. Attach a clear hose to the bleeder screw and submerge the other end in a container with clean brake fluid. Have an assistant pump the brake pedal 3-5 times and hold pressure. Open the bleeder screw 1/4 turn. Fluid and air will flow out. Close bleeder before pedal reaches floor. Repeat until no air bubbles appear in the hose and only clean fluid flows. Check reservoir level frequently and refill as needed. Torque bleeder screw to specification when complete.
    ⚠️Never let the master cylinder reservoir run empty during bleeding or you will introduce air and must start the bleeding process over.
14. 14

    Bleed remaining wheels in sequence
    Continue bleeding in this order: rear driver side, front passenger side, front driver side. Use the same procedure as step 13 for each wheel. The pedal should become progressively firmer as you complete each wheel. After bleeding all four wheels, the pedal should feel firm with no sponginess. Top off reservoir to MAX line and install cap.
    ⚠️If pedal remains spongy after bleeding all wheels, air remains in the system. Repeat bleeding process or seek professional service. Do not drive vehicle.
15. 15

    Reinstall wheels and perform initial testing
    Reinstall all wheels and torque lug nuts to specification in a star pattern. Lower vehicle to ground. Reconnect negative battery cable. With vehicle still stationary and engine off, pump brake pedal firmly 20-30 times. Pedal should feel firm and consistent. Check all brake line connections and master cylinder for any signs of fluid leakage. Check reservoir level and top off if needed.
    ⚠️Do not proceed to test drive if pedal feels spongy, travels too far, or if any leaks are visible. System must be re-bled or repaired.

Reassembly

1. Reinstall engine cover if it was removed
2. Clean any brake fluid spills from painted surfaces immediately using water
3. Dispose of old brake fluid according to local hazardous waste regulations
4. Remove protective coverings from fenders

Verification

• With engine off, pump brake pedal firmly 10 times - pedal should be firm and consistent with no excessive travel or sponginess
• Start engine - pedal should drop slightly as brake booster activates but remain firm
• Inspect all brake line connections at master cylinder for leaks with engine running
• Check master cylinder mounting nuts are tight and properly torqued
• Verify brake fluid level is at MAX line in reservoir
• Perform low-speed test drive in a safe area - test brakes at 5 mph, then 10 mph, then 15 mph to verify normal stopping power
• During test drive, verify pedal remains firm and vehicle stops in a straight line without pulling
• After test drive, recheck all connections for leaks and verify reservoir level
• If any abnormal pedal feel, noise, pulling, or reduced stopping power is detected, DO NOT DRIVE and seek professional service immediately

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