Replacement of the brake master cylinder on a 2024 Tesla Model Y Performance AWD. This job involves working adjacent to the iBooster electro-hydraulic brake unit and requires careful handling to avoid damaging the booster, brake lines, and surrounding aluminum bodywork.

Warnings

Tools required

Parts

• Brake master cylinder assembly (manufacturer-specified for 2024 Model Y Performance) × 1 — Refer to Tesla parts catalog for VIN-correct unit
• Master cylinder reservoir seal/grommet kit (if supplied separately) × 1 — OEM specification
• Brake line crush washers / sealing washers (if applicable) × 1 — OEM specification

Fluids

• DOT 3 Brake Fluid — 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/under the rear seat area on 2024 Model Y). Wait an additional 2 minutes after disconnection before working on the brake system to allow the iBooster capacitor to discharge.
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 / cowl access panels as needed to expose the master cylinder and brake fluid reservoir.
7. Place absorbent shop towels under the master cylinder area to catch fluid spillage — protect painted and aluminum surfaces.
8. Have the replacement master cylinder, fresh DOT 3 brake fluid, and bleeding equipment ready before opening the hydraulic system.

Procedure

1. 1

   Evacuate the brake fluid reservoir
   Using a clean turkey baster or fluid syringe, remove as much brake fluid as possible from the reservoir. Dispose of used fluid properly — do not reuse.
   ⚠Brake fluid will strip paint. Wipe spills immediately and rinse with water.
2. 2

   Disconnect electrical connectors
   Identify and disconnect the brake fluid level sensor connector at the reservoir, and any wiring harness clips routed across the master cylinder/booster assembly. Move the harness aside without straining it.
3. 3

   Identify and label brake line positions
   Before loosening anything, photograph and label each hydraulic line entering the master cylinder so they can be returned to their exact ports. Cross-connecting front/rear circuits will cause brake failure.
   ⚠️Incorrect line routing will result in unsafe braking. Verify each line's destination before disconnecting.
4. 4

   Disconnect brake lines from master cylinder
   Using a properly sized flare-nut (line) wrench, loosen each hydraulic line fitting at the master cylinder. Cap each line immediately with a clean cap or plug to prevent contamination and minimize fluid loss. Do not use a standard open-end wrench — it will round the soft fitting.
   ⚠Use only a flare nut / line wrench. Open-end wrenches will deform the fitting and may cause leaks on reassembly.
   Torque spec

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

   Remove the master cylinder mounting nuts
   Support the master cylinder by hand, then remove the nuts securing it to the brake booster studs. Note the orientation and any spacers, brackets, or ground straps for reinstallation.
   Torque spec

   Master Cylinder Nuts25 Nm (18 lb-ft)
6. 6

   Remove the master cylinder from the vehicle
   Carefully slide the master cylinder straight off the booster studs. Keep it level to avoid spilling residual fluid onto the booster or surrounding aluminum structure. Transfer the reservoir to the new unit only if the replacement does not include one — follow the manufacturer-specified seal/grommet replacement procedure.
   ⚠Do not allow fluid to drip onto the iBooster electronics or wiring connector.
7. 7

   Bench-bleed the new master cylinder
   Following the master cylinder manufacturer's instructions, bench-bleed the unit using the supplied bleed kit and fresh DOT 3 fluid before installing it on the vehicle. This removes air from the cylinder bores and dramatically reduces final bleed time.
8. 8

   Install the new master cylinder
   Position the new master cylinder onto the booster studs, ensuring it seats fully and squarely. Hand-thread the mounting nuts to prevent cross-threading, then torque evenly in an alternating pattern.
   ⚠Torque sequence is critical to prevent distortion of the master cylinder body. Verify sequence with the Tesla Service Manual.
   Torque spec

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

   Reconnect brake lines
   Start each hydraulic fitting by hand to confirm clean threading, then tighten with a flare-nut wrench to specification. Do not overtighten — these are soft fittings and will deform.
   Torque spec

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

    Reconnect electrical connectors and refill reservoir
    Reattach the fluid level sensor connector and any harness clips. Fill the reservoir to the MAX line with fresh DOT 3 brake fluid. Hand-tighten the reservoir cap.
11. 11

    Bleed the brake system
    Reconnect the 12V battery. Using a Tesla-compatible scan tool, perform the manufacturer-specified brake bleed routine that activates the ABS/iBooster pump. Then manually bleed each caliper in the manufacturer-specified sequence (typically furthest-to-nearest from the master cylinder), keeping the reservoir topped off throughout. Torque each bleeder screw to specification after bleeding.
    ⚠️The system MUST be bled with a scan tool that cycles the ABS module. Manual bleeding alone will leave air trapped in the iBooster/ABS unit, resulting in dangerous pedal feel.

Reassembly

1. Verify all brake line fittings are tight and dry — wipe each fitting with a clean rag and inspect for weeping after pressurization.
2. Top off the brake fluid reservoir to the MAX line with fresh DOT 3.
3. Reinstall the frunk liner and any cowl panels removed during prep.
4. Confirm the 12V battery is reconnected and secured.
5. Close the frunk and verify all electrical systems power up normally.

Verification

• With the vehicle off, press the brake pedal multiple times — it should feel firm and consistent, not spongy or sinking.
• Power on the vehicle and check the touchscreen for any brake system, ABS, traction control, or iBooster fault messages. Clear any stored DTCs with the scan tool and confirm they do not return.
• With the vehicle stationary in a safe area, perform a low-speed (under 10 mph) brake test to confirm normal pedal feel and stopping force before any road test.
• Road test at progressively higher speeds in an empty area, verifying ABS engagement on a hard stop functions normally.
• Inspect all fittings and the master cylinder body for leaks after the road test, both cold and after the system has been pressurized.
• Note the brake fluid service date — Tesla recommends a full brake fluid flush every 2 years regardless of mileage. Record this service in your maintenance log.

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