Inverter Coolant Service

This procedure involves draining, flushing, and refilling the inverter cooling system on the 2025 Rivian EDV 500 dual motor AWD electric delivery vehicle.

Warnings

Tools required

Parts

• Inverter coolant drain plug seal/washer × 2 — Use OEM specification
• Coolant system O-rings × 4 — Use OEM specification
• Underbody panel fasteners × 10 — Use OEM specification

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Park vehicle on level surface and ensure it is completely powered off
2. Allow cooling system to cool completely for minimum 2 hours if vehicle was recently operated
3. Disconnect 12V auxiliary battery negative terminal and wait 10 minutes
4. Raise vehicle on lift or jack stands to working height and ensure stability
5. Remove underbody protective panels to access inverter cooling system components
6. Place drip pans under inverter module and coolant routing areas
7. Verify high voltage system is de-energized using multimeter at service disconnect point
8. Connect diagnostic tool and document any pre-existing fault codes

Procedure

1. 1

   Access inverter coolant reservoir
   Locate the inverter coolant reservoir in the front compartment area. Remove any trim panels or covers obstructing access to the reservoir and coolant lines. The inverter cooling system is separate from the battery cooling system and uses its own dedicated reservoir.
2. 2

   Depressurize cooling system
   Slowly loosen the inverter coolant reservoir cap in stages to release any residual pressure. Remove cap completely once all pressure is released. Inspect cap seal for damage and replace if necessary.
3. 3

   Drain coolant from inverter system
   Locate the inverter coolant drain plug on the bottom of the front drive unit inverter housing. Position drain pan underneath. Remove drain plug and washer, allowing coolant to drain completely. This may take 15-20 minutes for full drainage. Inspect drain plug threads and washer condition.
4. 4

   Drain rear inverter coolant
   Move drain pan to rear drive unit position. Locate and remove the rear inverter coolant drain plug and washer. Allow complete drainage. If vehicle is equipped with dual inverter cooling circuits, both must be drained separately.
5. 5

   Remove coolant hoses for flushing
   Disconnect the upper and lower coolant hoses from both front and rear inverter assemblies. Label each connection for proper reassembly. Remove coolant lines from heat exchanger connections. Inspect all hose ends and connection points for corrosion or damage.
6. 6

   Flush inverter cooling passages
   Using a low-pressure coolant flushing tool or distilled water supply, flush each inverter cooling passage independently. Flow water through each circuit until discharge runs clear. Pay special attention to heat exchanger passages which can accumulate deposits. Do not exceed 20 PSI flushing pressure to avoid damaging internal components.
7. 7

   Inspect and replace sealing components
   Inspect all coolant hose O-rings, drain plug washers, and connection seals. Replace any seals showing wear, compression set, or damage. Clean all mating surfaces thoroughly before installing new seals. Apply thin film of coolant to O-rings before installation.
8. 8

   Reinstall drain plugs
   Install new drain plug washers on both front and rear inverter drain plugs. Thread plugs in by hand initially to ensure proper engagement. Tighten drain plugs to manufacturer specification. Without specific torque values provided, use conservative tightening to avoid thread damage while ensuring seal integrity.
9. 9

   Reconnect coolant hoses
   Reconnect all coolant hoses to their labeled positions on front and rear inverters and heat exchanger connections. Ensure O-rings are properly seated before pushing hoses fully onto connection points. Secure all hose clamps or quick-connect fittings per manufacturer design.
10. 10

    Fill inverter cooling system
    Using appropriate EV Battery/Motor Coolant, slowly fill the inverter coolant reservoir. Fill until coolant level reaches the cold fill line. Pour slowly to minimize air introduction into the system. Add approximately 10 quarts total, monitoring level as coolant fills passages.
11. 11

    Bleed air from cooling system
    Connect Rivian diagnostic tool and access the cooling system bleeding function. Follow on-screen prompts to activate coolant pumps in purge mode. This will circulate coolant and purge air from high points in the system. Monitor reservoir level and add coolant as needed during bleeding process. Continue bleeding cycle until no air bubbles are visible in reservoir and coolant level stabilizes.
12. 12

    Pressure test cooling system
    Install coolant pressure tester on reservoir. Pressurize system to 15 PSI and hold for 5 minutes. Inspect all connections, hoses, and inverter housings for leaks. System should hold pressure without loss. If pressure drops, locate and repair leak before proceeding.
13. 13

    Verify coolant concentration
    Extract small coolant sample from reservoir using turkey baster or similar tool. Test coolant concentration using refractometer or hydrometer. Verify proper mixture meets Rivian specifications for freeze and corrosion protection. Adjust if necessary.
14. 14

    Perform system function test
    Using diagnostic tool, command inverter cooling pump activation. Verify smooth pump operation without unusual noise. Check coolant circulation by feeling temperature of coolant lines after several minutes of operation. Monitor for proper flow through both front and rear circuits. Check for fault codes related to cooling system operation.

Reassembly

1. Reinstall all underbody protective panels using new fasteners as needed
2. Ensure all trim panels and covers are properly secured
3. Reconnect 12V auxiliary battery negative terminal
4. Top off coolant reservoir to cold fill line after system has stabilized
5. Clean any spilled coolant from vehicle surfaces and components

Verification

• Start vehicle and allow inverter cooling system to reach operating temperature while monitoring with diagnostic tool
• Verify no coolant leaks are present at any connections or seals after reaching operating temperature
• Confirm coolant level remains stable in reservoir between cold and hot fill marks
• Check for absence of cooling system fault codes using diagnostic tool
• Verify proper inverter operating temperatures during test drive (typically 40-70°C depending on load)
• Recheck coolant level after vehicle has cooled completely and top off if necessary
• Document service in vehicle maintenance records with date, mileage, and coolant type used

Related trouble codes on this vehicle

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