Inverter Coolant Service

Complete drain, flush, and refill of the electric motor and inverter cooling system on the Rivian EDV 500 dual motor AWD platform.

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

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Verify vehicle has been off for minimum 2 hours to allow cooling system to reach ambient temperature
2. Ensure work area is dry and non-conductive for high voltage safety
3. Connect Rivian diagnostic software and verify no active cooling system faults
4. Place vehicle on lift and raise to comfortable working height
5. Remove front and rear underbody panels to access inverter cooling system components
6. Locate both front and rear inverter coolant drain points beneath vehicle

Procedure

1. 1

   De-energize high voltage system
   Using Rivian diagnostic software, initiate high voltage system shutdown procedure. Remove HV service disconnect located in rear cargo area beneath access panel. Verify zero voltage at inverter terminals using high voltage meter. Install lockout/tagout device on HV service disconnect. Wait minimum 10 minutes for capacitors to discharge.
2. 2

   Relieve cooling system pressure
   Locate the inverter coolant reservoir cap in the front motor compartment. Slowly rotate cap counterclockwise to first detent to release system pressure. Wait for any hissing to stop, then remove cap completely. Inspect cap seal for damage and replace if necessary.
3. 3

   Drain front inverter coolant
   Position drain pan under front drive unit. Locate front inverter coolant drain plug on bottom of front motor housing. Remove drain plug and seal, allowing coolant to drain completely. Once drained, inspect drain plug threads and seal surface for damage. Replace drain plug seal with new component.
4. 4

   Drain rear inverter coolant
   Reposition drain pan under rear drive unit. Locate rear inverter coolant drain plug on bottom of rear motor housing. Remove drain plug and seal, allowing coolant to drain completely. Inspect drain plug threads and seal surface. Replace drain plug seal with new component.
5. 5

   Disconnect inverter coolant hoses
   Using hose clamp pliers, release clamps on coolant inlet and outlet hoses at both front and rear inverters. Carefully disconnect hoses, allowing any remaining coolant to drain into pan. Cap open hose ends to prevent contamination. Inspect hoses for cracks, swelling, or deterioration and replace if necessary.
6. 6

   Flush cooling system passages
   Connect low-pressure compressed air (maximum 20 PSI) to inverter coolant inlet ports. Blow out remaining old coolant from system. Follow with clean EV coolant flush through all passages to remove any debris or contaminated coolant. Continue flushing until discharge runs clear from all drain points.
7. 7

   Reinstall drain plugs
   Install new drain plug seals on both front and rear inverter drain plugs. Thread drain plugs into housings by hand to ensure proper engagement. Torque drain plugs to specification per manufacturer guidelines (torque specification not provided in database - consult service manual).
8. 8

   Reconnect coolant hoses
   Reconnect inverter coolant inlet and outlet hoses to both front and rear inverters. Ensure hoses are fully seated on fittings. Install new coolant hose clamps and position clamps away from hose ends. Tighten clamps securely but avoid over-tightening which can damage hoses.
9. 9

   Vacuum fill cooling system
   Connect vacuum fill tool to coolant reservoir. Draw vacuum on system to 25-28 inches Hg and hold for 5 minutes to check for leaks. If vacuum holds, open valve to draw in fresh EV Battery/Motor Coolant from supply container. Fill system with approximately 10 quarts of coolant or until reservoir reaches full cold mark.
10. 10

    Initial system pressurization
    Install coolant reservoir cap. Using diagnostic software, activate coolant pump in service mode to circulate coolant through system. Monitor for leaks at all connection points. Run pump for 3-5 minutes, then shut off and allow system to settle. Check reservoir level and add coolant as needed to maintain proper level.
11. 11

    Purge air from cooling system
    With diagnostic software still connected, initiate inverter cooling system bleed procedure. Software will cycle coolant pump and open bleed valves automatically. Monitor coolant level in reservoir and add coolant as air is purged from system. Continue bleeding process until no air bubbles visible in reservoir and level stabilizes.
12. 12

    Re-energize high voltage system
    Remove lockout/tagout device from HV service disconnect. Reinstall HV service disconnect and secure access panel. Using diagnostic software, command HV system to ready state. Verify proper voltage at inverter terminals and confirm no new fault codes are present.
13. 13

    Final coolant level verification
    With HV system energized, run coolant pump at full speed for 10 minutes using diagnostic software. Monitor coolant temperature rise to confirm proper circulation through inverters. After pump operation, allow system to cool for 30 minutes, then recheck coolant level and top off to full cold mark if needed.

Reassembly

1. Reinstall all underbody panels using new fasteners where necessary
2. Verify all coolant hose clamps are properly positioned and tightened
3. Clean any spilled coolant from underbody components and work area
4. Lower vehicle from lift

Verification

• Using diagnostic software, verify no cooling system fault codes are present
• Confirm coolant level is at full cold mark with system at ambient temperature
• Test coolant concentration using refractometer - should read proper freeze point per Rivian specification
• Perform short test drive and monitor inverter temperatures through diagnostic software - both inverters should maintain proper operating temperature range
• After test drive, recheck coolant level and inspect all connection points for leaks
• Clear service mode from vehicle computer and verify all systems return to normal operation

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