brakes

Brake Master Cylinder

for 2025 Rivian EDV 500 Dual Motor AWD (EDV) · AWD

Editorial review:Chris Hackleman — Master Technician · 20+ years · Jeff Moore — Master Lexus & Toyota Mechanic · 20+ years

Difficulty

Advanced

Time

2.0 h

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman & Jeff Moore — 20+ years each). Always follow the vehicle's factory service information and torque specs.

Remove and replace the brake master cylinder on a 2025 Rivian EDV 500, including brake line disconnection, electrical connector removal, and complete brake system bleeding.

Warnings

⚠️SAFETY CRITICAL: Brake system failure can result in loss of vehicle control and death. If you are uncertain about any step, have this work performed by a qualified technician.

⚠️This is an electric vehicle with high-voltage systems. Ensure the vehicle is fully powered down and HV system is de-energized before beginning work.

⚠️DOT 4 brake fluid is extremely corrosive to paint and toxic if ingested. Avoid skin contact and immediately flush any spills with water.

⚠Brake fluid absorbs moisture from air rapidly. Keep all containers sealed and use only fresh fluid from an unopened container.

⚠The Rivian EDV 500 uses integrated brake-by-wire technology. Master cylinder replacement requires electronic recalibration using Rivian diagnostic software.

ℹ️This procedure will result in complete loss of brake fluid. Have all parts and fluids ready before beginning.

Tools required

Flare nut wrench set (metric)Essential

Torque wrench (10-30 Nm range)Essential

Brake bleeding kit or pressure bleederEssential

Socket set (metric)

Brake fluid catch containerEssential

Turkey baster or fluid transfer pump

Clean lint-free ragsEssential

Multimeter

Rivian diagnostic tool or OBD-II scannerEssential

Parts

Brake master cylinder assembly × 1 — Use OEM Rivian specification
Master cylinder mounting nuts × 2 — Reuse if not damaged
Brake line sealing washers × 4 — Replace all

Fluids

DOT 4 Brake Fluid — 1.5 qt

Preparation

Park vehicle on level surface and engage parking brake
Place wheel chocks behind rear wheels
Power down the vehicle completely using the touchscreen: Vehicle Settings > Power Off
Wait 5 minutes for high-voltage system to fully discharge capacitors
Open hood and locate the 12V service disconnect under the front trunk. Disconnect 12V battery per service manual procedure
Remove the front trunk cargo area components to access the brake master cylinder area in the front compartment
Locate the brake master cylinder on the driver's side firewall area
Use turkey baster or fluid pump to remove as much brake fluid as possible from the master cylinder reservoir
Place absorbent cloths and a drain pan beneath the master cylinder work area

Procedure

1
Disconnect electrical connectors
Locate the brake fluid level sensor connector on the master cylinder reservoir cap. Press the locking tab and disconnect the electrical connector. If equipped with an electronic brake pressure sensor on the master cylinder body, disconnect that connector as well by pressing the release tab and pulling straight off. Mark connector orientation with tape if needed for reassembly.
2
Disconnect brake line from master cylinder - primary circuit
Using the appropriate size flare nut wrench (typically 11mm or 12mm), carefully loosen the primary brake line fitting at the master cylinder. Turn counterclockwise slowly to prevent rounding the fitting. Once loose, unscrew by hand and immediately cap the line end with a brake line plug or wrap with clean plastic wrap secured with a rubber band to prevent fluid loss and contamination. Allow residual fluid to drain into catch container.
Torque spec
Brake Line Fittings15 Nm (11 lb-ft)
3
Disconnect brake line from master cylinder - secondary circuit
Using the flare nut wrench, carefully loosen the secondary brake line fitting at the master cylinder. Turn counterclockwise to remove. Cap the line end immediately to prevent fluid loss and contamination. Note the routing and position of both brake lines for correct reassembly. Allow residual fluid to drain into catch container.
Torque spec
Brake Line Fittings15 Nm (11 lb-ft)
4
Remove master cylinder reservoir cap and drain remaining fluid
Carefully remove the reservoir cap. Use a fluid pump or turkey baster to remove all remaining brake fluid from both chambers of the reservoir. Dispose of old brake fluid according to local regulations. Wipe the reservoir interior with a clean lint-free cloth to check for debris or contamination.
5
Remove master cylinder mounting nuts
Locate the two mounting nuts securing the master cylinder to the brake booster or mounting bracket on the firewall. Using an appropriate socket (typically 13mm), remove both mounting nuts completely. Keep nuts in a safe place for reinstallation if they are in good condition.
Torque spec
Master Cylinder Nuts25 Nm (18 lb-ft)
6
Remove master cylinder from vehicle
Carefully pull the master cylinder straight forward off the mounting studs. The pushrod from the brake pedal assembly will separate from the master cylinder piston. Tilt the master cylinder to prevent spilling any remaining fluid. Place the old master cylinder in a suitable container. Inspect the pushrod and mounting area for damage or excessive wear.
7
Inspect mounting area and prepare new master cylinder
Inspect the brake booster mounting face and studs for corrosion or damage. Clean the mounting surface with brake cleaner and a lint-free cloth. Check that the pushrod moves freely and returns to the correct position. Verify the new master cylinder matches the original unit exactly. Install new sealing washers on all brake line fittings. Do not remove the shipping plugs from the new master cylinder ports yet.
8
Bench bleed the new master cylinder
Secure the new master cylinder in a vise with soft jaws, keeping it level. Remove shipping plugs from the outlet ports. Install bench bleeding tubes (supplied with master cylinder or purchased separately) into each outlet port, routing the tubes back into the reservoir chambers. Fill the reservoir with fresh DOT 4 brake fluid to the MAX line. Slowly depress the master cylinder piston using a wooden dowel or specialized tool, allowing it to return slowly. Repeat 15-20 times until no air bubbles emerge from the tubes. Remove tubes, install temporary plugs, and keep reservoir filled.
9
Install new master cylinder onto vehicle
Remove the temporary plugs from the master cylinder ports. Carefully align the master cylinder with the mounting studs and pushrod. Ensure the pushrod seats properly into the master cylinder piston bore. Push the master cylinder fully onto the studs until it contacts the mounting surface. Start both mounting nuts by hand to ensure proper thread engagement.
Torque spec
Master Cylinder Nuts25 Nm (18 lb-ft)
10
Torque master cylinder mounting nuts
Using a torque wrench, tighten both master cylinder mounting nuts to 25.0 Nm (18.0 lb-ft) in an alternating pattern to ensure even seating. Verify the master cylinder is seated flush against the mounting surface with no gaps.
Torque spec
Master Cylinder Nuts25 Nm (18 lb-ft)
11
Connect brake lines to master cylinder
Remove caps or plugs from the brake lines. Verify the new sealing washers are in place on each fitting. Thread the primary and secondary brake line fittings into the master cylinder ports by hand, ensuring they thread smoothly without cross-threading. Hand-tighten until snug. Using the flare nut wrench and torque wrench, tighten each brake line fitting to 15.0 Nm (11.0 lb-ft). Do not overtighten as this can damage the flare seat and cause leaks.
Torque spec
Brake Line Fittings15 Nm (11 lb-ft)
12
Reconnect electrical connectors and fill reservoir
Reconnect the brake fluid level sensor connector to the reservoir cap, ensuring it clicks into place. Reconnect any additional brake pressure sensor connectors if equipped. Fill the master cylinder reservoir with fresh DOT 4 brake fluid from an unopened container to the MAX line. Install the reservoir cap.
13
Bleed the brake system
Bleed the entire brake system starting with the wheel furthest from the master cylinder (typically right rear) and proceeding to right front, left rear, then left front. Use a pressure bleeder or two-person manual bleeding method. At each wheel, attach a clear tube to the bleeder screw and submerge the other end in clean brake fluid in a container. Open the bleeder screw and allow fluid to flow until no air bubbles appear. Close the bleeder screw before releasing pedal pressure. Keep the master cylinder reservoir filled throughout the process. Repeat for all four wheels.
14
Perform electronic brake system calibration
Reconnect the 12V battery service disconnect. Power on the vehicle. Connect the Rivian diagnostic tool or compatible OBD-II scanner with Rivian software access. Navigate to the brake system control module and perform the master cylinder replacement initialization procedure. This recalibrates the brake-by-wire system and electronic stability control. Follow all on-screen prompts. Clear any stored fault codes after successful calibration.

Reassembly

Reinstall all front trunk cargo area components that were removed for access
Verify all electrical connections are secure and properly routed
Check the master cylinder reservoir fluid level and top off to MAX line with fresh DOT 4 brake fluid if needed
Verify no brake fluid leaks are present at the master cylinder or brake line connections
Close the hood securely

Verification

With the vehicle powered on, verify the brake warning light is NOT illuminated on the instrument cluster
Check for any brake system fault codes using the diagnostic tool
Pump the brake pedal 10-15 times with the vehicle off. The pedal should feel firm with no excessive travel or spongy feel
Start the vehicle and verify the brake pedal remains firm and does not slowly sink when held under moderate pressure for 30 seconds
Perform a low-speed brake test in a safe area (under 5 mph) to verify proper brake function and pedal feel
Inspect all brake line connections at the master cylinder for any signs of fluid leakage
Perform a complete brake system pressure test if available, verifying system holds pressure within manufacturer specifications
Test drive the vehicle in a safe area at increasing speeds, verifying normal brake operation, proper pedal feel, and no warning lights
After test drive, re-inspect all connections for leaks and recheck brake fluid level
If any abnormality is detected, do not drive the vehicle and consult a professional immediately