Complete coolant flush and replacement for the Rivian EDV 500's dual motor and battery thermal management system, including draining, flushing, and refilling with EV-specific coolant.

Warnings

Tools required

Parts

• Coolant drain plug O-ring (battery pack) × 1 — Use OEM specification
• Coolant drain plug O-ring (motor unit) × 1 — Use OEM specification
• Lower splash shield clips × 5 — Use OEM specification
• Expansion tank cap gasket × 1 — Use OEM specification

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Park vehicle on level surface and apply parking brake. Place wheel chocks behind rear wheels.
2. Ensure the vehicle has been shut down for at least 2 hours to allow coolant system to cool and depressurize.
3. Verify the 12V battery is fully charged (electric vehicles rely on 12V system for service mode functions).
4. Disconnect the 12V battery negative terminal and wait 5 minutes to ensure all systems are de-energized.
5. Remove the front undertray and lower splash shields to access coolant drain points.
6. Raise and safely support the front of the vehicle on jack stands if additional access is needed.
7. Place large drain pan under the vehicle positioned to catch coolant from multiple drain points.
8. Connect diagnostic tool and verify communication with vehicle control modules before proceeding.

Procedure

1. 1

   Access coolant expansion tank
   Open the front hood and locate the coolant expansion tank on the driver's side of the front trunk area. Remove the plastic cover panel by releasing the retaining clips. Carefully remove the expansion tank cap by turning counterclockwise, allowing any residual pressure to release slowly. Inspect the cap gasket for damage and replace if necessary.
2. 2

   Drain battery pack coolant circuit
   Locate the battery pack coolant drain plug on the underside of the vehicle, positioned near the center of the battery pack assembly. Using a 13mm socket, carefully remove the drain plug and allow coolant to drain completely into the catch pan. This circuit contains approximately 5 quarts. Once drained, inspect the drain plug O-ring and replace with new O-ring.
3. 3

   Drain motor cooling circuit
   Locate the motor cooling circuit drain plug beneath the front motor assembly. Remove the drain plug using appropriate socket and drain the motor coolant circuit completely (approximately 3-4 quarts). Inspect and replace the motor drain plug O-ring with a new component.
4. 4

   Drain coolant from expansion tank and lines
   Using a fluid extraction pump or by disconnecting the lower coolant hose at the expansion tank (if accessible), remove remaining coolant from the expansion tank and associated lines. This ensures maximum old coolant removal. Have drain pan positioned to catch any spillage from hose disconnection.
5. 5

   Perform cooling system flush (optional but recommended)
   If performing a full flush, reconnect drain plugs with new O-rings hand-tight only. Add distilled water to the expansion tank to approximately 50% capacity. Reconnect 12V battery temporarily. Using the diagnostic tool, activate the coolant pump circulation in service mode for 2-3 minutes. Shut down, disconnect 12V battery again, and re-drain all circuits completely. Repeat this process once more with fresh distilled water to ensure contamination removal.
6. 6

   Reinstall drain plugs with new O-rings
   Install new O-rings on both the battery pack and motor drain plugs. Thread drain plugs in by hand first to ensure proper alignment, then tighten securely with socket wrench. Do not overtighten as drain plugs thread into aluminum housings. Tighten until snug plus approximately 1/4 turn beyond O-ring contact.
7. 7

   Connect vacuum fill tool
   Attach the coolant vacuum fill tool to the expansion tank opening. Ensure a proper seal to maintain vacuum. This tool is essential for EV cooling systems to prevent air pockets in the battery and motor thermal management circuits which can cause hotspots and system faults.
8. 8

   Create vacuum and fill cooling system
   Operate the vacuum fill tool to create a vacuum of at least 20 inches of mercury in the cooling system. Hold vacuum for 2 minutes to verify system integrity (vacuum should not drop). Once vacuum is confirmed, open the fill valve and allow the system to draw in the Rivian-approved EV coolant. The system will require approximately 10 quarts total. Monitor the fill process and add coolant as needed until the system stops drawing fluid.
9. 9

   Remove vacuum tool and initial fill completion
   Once vacuum filling is complete and no more coolant is being drawn in, carefully remove the vacuum fill tool. Top off the expansion tank to the MAX cold fill line marked on the tank. Do not overfill as coolant will expand when the system reaches operating temperature.
10. 10

    Reconnect 12V battery and initialize system
    Reconnect the 12V battery negative terminal. Using the diagnostic tool, clear any stored fault codes related to the cooling system. Initialize the thermal management system through the service menu to prepare for circulation and bleeding procedures.
11. 11

    Perform thermal management system bleed procedure
    With the diagnostic tool, enter service mode and activate the 'Thermal Management Bleed' procedure. This will cycle the coolant pumps through multiple circuits at varying speeds to purge any remaining air. The procedure typically runs for 10-15 minutes. Monitor coolant level in the expansion tank and add coolant as needed during this process. The level may drop as air is purged from the system.
12. 12

    Pressure test cooling system
    Using the diagnostic tool, command the thermal management system to high-speed circulation mode. Monitor system pressure and temperatures through the diagnostic interface. System pressure should stabilize between 10-15 PSI when circulating. Check all connections, drain plugs, and hoses for any signs of leakage. Allow system to circulate for 5 minutes while monitoring.
13. 13

    Final coolant level adjustment
    After the circulation and bleed procedure is complete, shut down the system and wait 5 minutes for coolant to settle. Check the expansion tank coolant level and adjust to the MAX cold fill line as needed. Install the expansion tank cap with new gasket if original showed signs of wear, ensuring it is properly seated and tightened.

Reassembly

1. Reinstall the front undertray and lower splash shields, ensuring all clips and fasteners are properly secured.
2. Reinstall any plastic covers or panels removed during the procedure.
3. Lower the vehicle if it was raised on jack stands.
4. Remove wheel chocks and verify all tools and equipment have been removed from the vehicle.
5. Clean up any spilled coolant from vehicle surfaces and floor to prevent slipping hazards.

Verification

• Using the diagnostic tool, verify no fault codes are present in any thermal management system modules.
• Check coolant level in expansion tank is at MAX cold fill line with system cold.
• Inspect all drain plugs, connections, and hoses for any signs of coolant leakage.
• If possible, perform a short test drive (2-3 miles) and monitor thermal management system temperatures through diagnostic tool to verify proper operation.
• After test drive, recheck coolant level when system has cooled and top off if necessary to MAX line.
• Verify cooling system pressure holds steady with no drops that would indicate leaks.
• Document the service date and coolant specification used for vehicle maintenance records.
• If available, use a coolant hydrometer or refractometer to verify proper coolant concentration and freeze protection rating.

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