Complete flush and replacement of the EV battery and motor cooling system coolant to maintain optimal thermal management of the high-voltage drive system.

Warnings

Tools required

Parts

• Coolant drain plug O-ring × 1 — Use OEM specification
• Lower coolant hose clamp (if damaged) × 1 — Use OEM specification

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Ensure vehicle has been off and cooling for minimum 2 hours
3. Open driver's door to maintain communication with vehicle computer systems
4. Disconnect 12V negative battery terminal and wait 15 minutes for high-voltage system discharge
5. Using Rivian diagnostic tool, verify HV system is safe to work (no voltage present)
6. Raise vehicle on lift or jack stands ensuring proper weight distribution for safe support
7. Remove front undertray and lower belly pan panels to access drain points
8. Place absorbent pads under work area to catch coolant spills

Procedure

1. 1

   Access and identify coolant drain points
   Locate the primary coolant drain valve on the lower driver's side of the battery pack thermal management plate. Identify the secondary drain point at the rear motor cooling circuit junction near the rear differential. Note the fill port location on top of the motor cooling reservoir in the front trunk area.
2. 2

   Drain battery cooling circuit
   Position drain pan under battery pack drain valve. Open the primary drain valve by rotating counterclockwise. Allow coolant to drain completely (approximately 4-5 quarts). Watch for flow to stop completely indicating circuit is empty. Remove and inspect drain plug O-ring for damage.
3. 3

   Drain motor cooling circuits
   Reposition drain pan under rear motor drain point. Locate and open the rear motor coolant drain fitting. Allow complete drainage (approximately 3-4 quarts). Access front motor drain point through wheel well and drain remaining coolant (approximately 2-3 quarts). Keep drained coolant separate for disposal inspection.
4. 4

   Remove and clean coolant reservoir
   Open front trunk and locate the coolant expansion reservoir. Disconnect the electrical connector for the coolant level sensor. Remove reservoir mounting bolts and carefully lift reservoir out. Drain any remaining coolant. Inspect reservoir interior for sediment or contamination and clean thoroughly with distilled water if needed.
5. 5

   Flush cooling system circuits
   Connect coolant flush adapter to the reservoir mounting point. Using distilled water only, flush each circuit individually starting with battery circuit, then rear motor, then front motor. Continue flushing each circuit until discharge water runs completely clear. Allow all circuits to drain completely after flushing.
6. 6

   Reinstall drain plugs and reservoir
   Install new O-ring on battery pack drain plug. Install and hand-tighten drain plug, then snug firmly (do not overtighten as housing is aluminum). Close rear and front motor drain fittings. Reinstall cleaned coolant reservoir with new mounting hardware if needed. Reconnect coolant level sensor electrical connector.
7. 7

   Fill battery cooling circuit
   Using proper EV Battery/Motor Coolant only, slowly fill the system through the reservoir. Pour approximately 4 quarts initially and allow time for coolant to migrate through battery cooling channels. Watch reservoir level and maintain fill as coolant distributes. Stop when level reaches cold fill line on reservoir.
8. 8

   Fill motor cooling circuits and initial bleed
   Continue filling with additional 4 quarts of coolant. Connect Rivian diagnostic tool and access thermal management bleeding procedure. Activate electric coolant pump in purge mode to circulate coolant and purge air from motor circuits. Monitor reservoir level and add coolant as air is expelled. Run purge cycle for 10 minutes.
9. 9

   Complete system bleeding procedure
   Using diagnostic tool, initiate full thermal management system bleed sequence. System will cycle pumps and open valves in specific sequence to remove all air. Process takes approximately 15-20 minutes. Monitor reservoir closely and add coolant as needed to maintain proper level. Watch for air bubbles in reservoir to decrease and stop.
10. 10

    Pressure test and leak inspection
    With diagnostic tool, pressurize the cooling system to test pressure (approximately 15 PSI). Carefully inspect all drain points, hoses, connections, and reservoir for any signs of leakage. Check battery pack perimeter and motor housings for coolant seepage. Hold pressure for 5 minutes and verify no pressure loss.
11. 11

    Final fill and system verification
    Top off coolant to proper cold fill level (approximately 2 quarts additional may be needed after bleeding). Install reservoir cap securely. Using diagnostic tool, verify all cooling system sensors are reading properly: coolant temperature, flow rate, and level sensors should all show normal values. Clear any diagnostic codes related to low coolant level.

Reassembly

1. Reinstall front belly pan and undertray panels ensuring all clips and fasteners are secure
2. Lower vehicle from jack stands or lift
3. Reconnect 12V negative battery terminal
4. Close all doors and allow vehicle systems to initialize
5. Top off coolant reservoir to proper cold level if needed after vehicle systems activate

Verification

• With vehicle in accessory mode, verify no thermal management warning messages on instrument cluster
• Using diagnostic tool, confirm all coolant temperature sensors show ambient temperature (within 5°F of each other)
• Verify coolant level sensor shows full status on vehicle display
• Test drive vehicle for 15 minutes in mixed driving conditions to bring cooling system to operating temperature
• After test drive and cool-down period (30 minutes), recheck coolant level and top off if needed (up to 0.5 quart is normal after first heat cycle)
• Verify no coolant leaks visible under vehicle after test drive
• Clear any residual diagnostic codes and confirm no new thermal management faults present
• Document coolant concentration with refractometer (should read proper freeze protection per Rivian specifications)

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