Inverter Coolant Service

Complete coolant system service for the Rivian EDV 500 dual motor inverter cooling system, including drain, flush, and refill with EV-specific coolant.

Warnings

Tools required

Parts

• Inverter coolant drain plug seal × 2 — Use OEM specification
• Coolant hose clamps × 4 — Use OEM specification
• Underbody panel fasteners × 10 — Use OEM specification
• Expansion tank cap seal × 1 — Replace if damaged

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Ensure vehicle has been off for minimum 3 hours to allow coolant system to cool
3. Connect Rivian diagnostic software and verify no active high voltage system faults
4. Using diagnostic software, place vehicle in service mode and disable high voltage system
5. Verify high voltage system is de-energized using digital multimeter at service disconnect location
6. Remove front underbody panels to access inverter cooling system components
7. Place coolant drain pan beneath vehicle positioned under front drive unit area
8. Document current coolant level and condition through expansion tank sight glass
9. Photograph underhood component positions and hose routing for reassembly reference

Procedure

1. 1

   Access inverter coolant system
   Remove driver side front wheel for improved access. Remove additional underbody panels as needed to expose front and rear drive unit inverter cooling lines. Locate the inverter coolant expansion tank in the front compartment and remove the cap slowly to release any residual pressure.
2. 2

   Drain front inverter coolant circuit
   Position drain pan under front drive unit. Locate the coolant drain valve on the front inverter cooling plate. Open the drain valve slowly and allow coolant to drain completely into the pan. If no drain valve is present, disconnect the lowest coolant hose from the front inverter assembly using hose clamp pliers to release the spring clamps.
3. 3

   Drain rear inverter coolant circuit
   Reposition drain pan under rear drive unit area. Access the rear inverter through the rear underbody panels. Open the rear inverter drain valve or disconnect the lowest coolant return line. Allow system to drain completely, which may take 15-20 minutes due to system complexity.
4. 4

   Drain expansion tank and coolant reservoir
   Remove the expansion tank from its mounting bracket by releasing the securing clips. Pour remaining coolant into drain pan. Inspect tank interior for contamination, sediment, or discoloration. Clean tank with deionized water if sediment is present. Inspect tank cap seal and replace if worn or damaged.
5. 5

   Flush inverter cooling circuits
   Connect flush tool to the inverter coolant inlet line at the expansion tank connection. Using deionized water only, flush the front inverter circuit until discharge runs clear. Repeat process for rear inverter circuit. Do not use chemical flush additives as they may damage EV cooling system components.
6. 6

   Inspect coolant system components
   Visually inspect all coolant hoses for cracks, swelling, or degradation. Check all hose connections and clamps for security. Inspect inverter cooling plate surfaces for signs of leakage or corrosion. Check coolant pump electrical connections for security and corrosion. Replace any damaged components before proceeding.
7. 7

   Reconnect coolant lines
   Reconnect all coolant hoses to their original positions using reference photos. Replace spring-type hose clamps with new clamps if originals show signs of weakening. Ensure all drain valves are closed securely. Install drain plug seals on both front and rear inverter drain points.
8. 8

   Reinstall expansion tank
   Clean expansion tank mounting area and reinstall tank into mounting bracket. Ensure all securing clips are fully engaged. Reconnect coolant lines to expansion tank in correct positions. Verify coolant level sensor connector is properly seated.
9. 9

   Vacuum fill cooling system
   Connect vacuum fill tool to expansion tank fill port. Draw vacuum on system to -25 inHg minimum and hold for 5 minutes to verify system integrity. If vacuum does not hold, locate and repair leak. Once vacuum test passes, introduce fresh EV Battery/Motor Coolant through vacuum fill tool until system is filled to appropriate level, approximately 10 quarts total.
10. 10

    Perform initial system bleed
    With expansion tank cap loosely installed, use Rivian diagnostic software to activate coolant pump in service mode. Run pump for 2 minutes, then check coolant level and top off as needed. Repeat this process 3 times to circulate coolant through entire system and purge initial air pockets.
11. 11

    Pressure test cooling system
    Install cooling system pressure tester to expansion tank. Pressurize system to 15 PSI and hold for 10 minutes. Monitor for pressure drop indicating leaks. Inspect all connections, hoses, and inverter cooling plates for evidence of leakage. Repair any leaks found and retest.
12. 12

    Run diagnostic system bleed procedure
    Using Rivian diagnostic software, initiate the automated inverter coolant bleeding procedure. This will cycle the coolant pump through specific patterns and activate electric heaters to expand coolant and release trapped air. Process takes approximately 30 minutes. Monitor coolant level throughout and add coolant as needed.
13. 13

    Verify coolant circulation
    With diagnostic software, monitor coolant temperatures at front inverter, rear inverter, and expansion tank. Temperatures should equalize within 5 degrees Celsius after 10 minutes of circulation, indicating proper flow through both circuits. If temperatures do not equalize, repeat bleeding procedure.
14. 14

    Final coolant level adjustment
    With system at operating temperature (approximately 50 degrees Celsius), check coolant level at expansion tank. Fill to the HOT mark on the sight glass. Install expansion tank cap securely. Allow system to cool and recheck level at cold temperature, adjusting to COLD mark if necessary.

Reassembly

1. Reinstall all underbody panels and secure with new fasteners where necessary
2. Reinstall driver side front wheel and torque lug nuts to specification
3. Clean any spilled coolant from underbody and components
4. Using diagnostic software, clear service mode and re-enable high voltage system
5. Reset coolant service interval in vehicle computer if applicable

Verification

• Using diagnostic software, verify no coolant system fault codes are present
• Check expansion tank coolant level at cold temperature and confirm at proper level on sight glass
• Visually inspect all connection points for signs of leakage with vehicle on lift
• Test drive vehicle for minimum 15 minutes, including highway speeds and low-speed maneuvering
• After test drive, recheck coolant level and inspect for leaks again
• Verify inverter temperatures remain within normal range (typically 40-70°C) using diagnostic software during and after test drive
• Confirm coolant pump operation by listening for pump noise and monitoring temperature changes in diagnostic software
• Instruct owner to monitor coolant level warning light and check level after first 100 miles of driving

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