Replacement of the brake master cylinder on a 2024 Model X Long Range. The job requires careful brake fluid handling, line disconnection, and a proper bleed procedure afterward — note that the iBooster/electric brake booster assembly on this vehicle is integrated and may require Tesla diagnostic tooling for a full system bleed.

Warnings

Tools required

Parts

• Brake master cylinder assembly (OEM-spec for 2024 Model X) × 1 — Manufacturer-specified replacement — verify by VIN
• Reservoir-to-master-cylinder seals / grommets × 1 — Included with master cylinder or order separately if not included
• Brake line sealing washers (if used at fittings) × 1 — OEM specification

Fluids

• DOT 3 Brake Fluid (sealed, fresh container) — 1 qt

Preparation

1. Park on level ground, place in P, engage parking brake.
2. Exit ALL doors with the key fob away from the vehicle. Wait at least 2 minutes for HV systems to fully de-energize, even on this non-HV job.
3. Disconnect the 12V low-voltage battery in the frunk (similar position to Model S). Follow the cover removal and negative-terminal-first procedure.
4. DO NOT touch, cut, or pierce ANY orange cable — these are high-voltage and lethal.
5. If at any point you encounter an orange cable, an HV component, or are unsure if a system is de-energized: STOP and consult a Tesla-certified technician.
6. Open the frunk and locate the brake fluid reservoir. Cover surrounding aluminum panels and paint with absorbent material — brake fluid will damage finish.
7. Have a fresh, sealed bottle of DOT 3 brake fluid ready. Do not use previously opened fluid.
8. Confirm Falcon doors are closed and will remain closed during the procedure to avoid accidental actuation when 12V is reconnected.

Procedure

1. 1

   Access the master cylinder
   Remove any frunk liner, cowl trim, or covers necessary to access the brake master cylinder and booster assembly. Use trim tools to avoid breaking clips. Note routing of any wiring harnesses for reinstallation.
2. 2

   Evacuate the brake fluid reservoir
   Using a clean turkey baster or fluid extractor, remove as much brake fluid as possible from the reservoir. Dispose of used fluid properly — do not reuse.
   ⚠Do not let brake fluid drip onto aluminum body panels or painted surfaces.
3. 3

   Disconnect electrical connectors
   Disconnect the fluid level sensor connector at the reservoir and any other connectors on or near the master cylinder/booster assembly. Set harnesses aside, secured away from the work area.
4. 4

   Disconnect brake lines from the master cylinder
   Place a catch pan beneath the master cylinder. Using a flare nut / line wrench (never an open-end wrench), carefully loosen each brake line fitting at the master cylinder. Note the position of each line for reinstallation. As fittings come free, cap or plug each line immediately to minimize fluid loss and contamination.
   ⚠Use only a flare nut/line wrench — open-end wrenches will round the soft fittings.
   Torque spec

   Brake Line Fittings15 Nm (11 lb-ft)
5. 5

   Remove the reservoir (if separate)
   If the reservoir mounts to the master cylinder via grommets, gently rock and pull it upward to free it. If it is hard-piped or shared with the booster, leave it in place per the service manual. Inspect grommets and replace if cracked or hardened.
6. 6

   Remove the master cylinder mounting nuts
   Support the master cylinder with one hand. Loosen and remove the nuts securing the master cylinder to the brake booster in a cross/even pattern. Withdraw the master cylinder straight off the booster studs to avoid bending the input rod or damaging the booster seal.
   ⚠Do not pry against aluminum surfaces or strike the booster — Model X uses an aluminum body structure that dents easily.
   Torque spec

   Master Cylinder Nuts25 Nm (18 lb-ft)
7. 7

   Bench-prep the new master cylinder
   Bench-bleed the new master cylinder per the manufacturer's instructions before installation: install the supplied bleed fittings/hoses, fill with fresh DOT 3 fluid, and stroke the piston until no air bubbles return to the reservoir. This is essential for proper pedal feel.
   ⚠Skipping bench bleeding will likely result in a spongy pedal that cannot be corrected at the wheels.
8. 8

   Install the new master cylinder
   Align the new master cylinder onto the booster studs, ensuring the pushrod seats correctly. Hand-thread both nuts, then torque evenly in a cross pattern. Verify sequence with the Tesla Service Manual.
   Torque spec

   Master Cylinder Nuts25 Nm (18 lb-ft)
9. 9

   Reconnect brake lines
   Hand-start each brake line fitting into its correct port to avoid cross-threading the soft thread. Once all fittings are started, snug them, then torque to specification using a flare nut wrench. Verify line routing matches original.
   ⚠Cross-threading a brake line fitting will require master cylinder replacement again. Always start by hand.
   Torque spec

   Brake Line Fittings15 Nm (11 lb-ft)
10. 10

    Reinstall reservoir and reconnect sensors
    If the reservoir was removed, reinstall it onto fresh/inspected grommets and seat fully. Reconnect the fluid level sensor and any other connectors disturbed.
11. 11

    Fill and bleed the brake system
    Fill the reservoir with fresh DOT 3 brake fluid to the MAX line. Perform a full four-corner bleed starting from the caliper farthest from the master cylinder, working toward the closest, using the bleeder screws. Keep the reservoir topped up throughout. For a complete bleed of the integrated electronic booster and ABS modulator, use Tesla diagnostic tooling to cycle the system — without it, pedal feel may not be fully restored.
    ⚠Never let the reservoir run dry during bleeding — this introduces air into the ABS/booster and dramatically complicates the bleed.
12. 12

    Cap reservoir and clean up
    Top off to MAX with fresh DOT 3 fluid. Install the reservoir cap hand-tight. Thoroughly clean any spilled fluid with water and dry the area.

Reassembly

1. Reinstall any cowl trim, frunk liner, and covers removed for access.
2. Reconnect the 12V battery (positive first, then negative), and reinstall its cover.
3. Allow the vehicle to wake and complete its initial power-on self-checks before pressing the brake pedal.

Verification

• With the vehicle off, pump the brake pedal several times — it should become firm and not sink to the floor.
• Power on the vehicle and check the instrument display for any brake, ABS, traction control, or stability warnings. Address any DTCs with Tesla diagnostic tooling.
• Inspect every disturbed fitting and the master cylinder body for leaks after pressurizing the system.
• Test drive at low speed in a safe area: confirm firm pedal, straight braking with no pull, and no warning messages on the touchscreen.
• Re-inspect for leaks after the test drive and recheck reservoir level.
• Record this service — brake fluid replacement is recommended every 2 years on Tesla vehicles regardless of mileage; resetting this interval is appropriate since the system has been refilled with fresh fluid.

More procedures for this vehicle