Replacement of the brake master cylinder on a 2024 Tesla Model 3 Performance. This is a hydraulic-system job — no HV components are touched, but the iBooster-style integrated brake system requires careful fluid handling and a proper bleed procedure afterward.

Warnings

Tools required

Parts

• Brake master cylinder assembly (Model 3 Performance specific) × 1 — Manufacturer-specified Model 3 master cylinder — verify with VIN
• Master cylinder reservoir seal/grommets (if supplied separately) × 1 — OEM seal kit
• Brake fluid (sealed container) × 1 — DOT 4 — per Tesla architecture spec

Fluids

• DOT 4 brake fluid (Tesla-specified) — 1 qt

Preparation

1. Park on level ground, place in P, engage parking brake.
2. Exit ALL doors with 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 (located behind the right rear seat back panel on most 2024 Model 3 vehicles; some 2024+ units use a lithium 12V under the floor — consult vehicle-specific documentation).
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 remove the frunk liner / front trunk tub to access the brake master cylinder area.
7. Place absorbent shop towels and fender covers around the master cylinder — Model 3 has aluminum panels in this area that brake fluid will damage.
8. Have a sealed bottle of fresh DOT 4 brake fluid ready; do not use fluid from a previously opened container.

Procedure

1. 1

   Verify 12V is disconnected and area is safe
   Confirm the 12V battery negative is disconnected and isolated. Verify no orange HV cabling is in the immediate workspace. The master cylinder/booster assembly is mounted to the firewall in the front trunk area.
   ⚠️If any orange cable is visible or in the way, stop work immediately.
2. 2

   Evacuate the brake fluid reservoir
   Remove the reservoir cap and use a clean fluid evacuator or syringe to remove as much brake fluid as possible from the reservoir. Dispose of used fluid properly — do not reuse.
3. 3

   Disconnect electrical connectors
   Carefully release and disconnect the electrical connector(s) at the master cylinder/booster assembly (fluid level sensor and any booster control connectors). Move harnesses aside and protect them from fluid drips.
4. 4

   Identify and label brake line fittings
   Before loosening, photograph and label each hydraulic line going into the master cylinder so each line returns to its original port. The Model 3 master cylinder has multiple outlet ports — mis-routing will cause incorrect circuit operation.
5. 5

   Disconnect brake lines from master cylinder
   Using the correct size line/flare-nut wrench, slowly loosen each brake line fitting at the master cylinder. Allow residual fluid to drain into a catch pan. Cap each line immediately to prevent contamination and minimize fluid loss. Take care not to round the soft fitting hex.
   ⚠Use a line wrench, never an open-end wrench — fittings are soft and round easily.
   Torque spec

   Brake Line Fittings15 Nm (11 lb-ft)
6. 6

   Remove the reservoir (if separate from master cylinder)
   If the reservoir is supplied separately from the new master cylinder, gently rock and pull the reservoir upward off the master cylinder grommets. Inspect the grommets — replace if hardened or torn.
7. 7

   Remove master cylinder mounting nuts
   Support the master cylinder from below. Remove the mounting nuts that secure the master cylinder to the brake booster/firewall in an even, alternating pattern to avoid binding the studs.
   ⚠Verify removal sequence with the Tesla Service Manual — the integrated booster assembly may require a specific loosening pattern.
   Torque spec

   Master Cylinder Nuts25 Nm (18 lb-ft)
8. 8

   Remove the master cylinder from the vehicle
   Carefully slide the master cylinder straight off the booster studs. Avoid contact with painted surfaces. Place in a drain pan immediately as residual fluid will continue to weep from the ports.
9. 9

   Bench-bleed the new master cylinder
   Mount the new master cylinder in a soft-jaw vise. Install the manufacturer-supplied bench bleeding fittings and tubing, fill the reservoir with fresh DOT 4 fluid, and stroke the piston with a smooth tool until no air bubbles return to the reservoir. This step is essential — installing a dry master cylinder will make on-vehicle bleeding extremely difficult.
10. 10

    Install the new master cylinder
    Transfer the reservoir (if applicable) onto the new master cylinder using new grommets. Slide the master cylinder onto the booster studs, ensuring the pushrod aligns correctly. Install the mounting nuts finger-tight first, then torque evenly in an alternating pattern to the manufacturer-specified value.
    Torque spec

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

    Reconnect brake lines
    Thread each brake line fitting in by hand first to avoid cross-threading the soft fittings. Once all lines are started, torque each fitting to specification using a line wrench. Refer to the labels/photos taken in Step 4 to ensure correct routing.
    Torque spec

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

    Reconnect electrical connectors
    Reconnect any sensor and booster electrical connectors removed earlier. Verify each is fully seated and locked.
13. 13

    Fill reservoir and perform initial bleed
    Fill the reservoir to the MAX line with fresh DOT 4 brake fluid. Perform a gravity bleed at each caliper bleeder, then a pressure or two-person bleed in the manufacturer-specified sequence. Maintain reservoir level above MIN at all times.
14. 14

    Reconnect 12V and run service-tool brake bleed routine
    Reconnect the 12V battery. Use Tesla Toolbox or an equivalent diagnostic tool capable of running the iBooster/ABS auto-bleed routine. This cycles internal valves and the electronic booster to purge air that manual bleeding cannot reach. Re-bleed each caliper after the auto-bleed completes.
    ⚠Skipping the electronic auto-bleed will leave trapped air in the booster/ABS module, resulting in a soft pedal and potential brake performance degradation.
15. 15

    Final fluid level and cap
    Top reservoir to the MAX line with fresh DOT 4. Install the reservoir cap hand-tight to the specified torque. Wipe down all surfaces with water to remove any fluid residue.

Reassembly

1. Reinstall the frunk liner / front trunk tub.
2. Confirm reservoir cap is seated and labeled with the service date.
3. Clear any DTCs stored during service using the diagnostic tool.
4. Verify pedal feel is firm before moving the vehicle — pump the pedal multiple times with the vehicle off, then with it on, confirming the pedal does not sink.

Verification

• With the vehicle powered on, confirm no brake-related warnings appear on the center display (no ABS, traction control, iBooster, or brake fluid warnings).
• Inspect every brake line fitting and the master cylinder mounting flange for weeping after 5 minutes of pedal pressure.
• Perform a low-speed (5-10 mph) brake test in a safe area; pedal should be firm with no pulsation, no pull, and no extended travel.
• At 20-25 mph, perform a moderate stop and confirm regen + friction blending feels normal — abnormal pedal travel or warning lights mean air is still in the system; repeat the auto-bleed.
• Recheck reservoir level after the test drive and top off if needed.
• Note: Tesla recommends a complete brake fluid flush every 2 years regardless of mileage. Log this service date so the next flush is scheduled appropriately.

More procedures for this vehicle