EV Thermal Management System

Diagnostic inspection and maintenance procedure for the EV thermal management system, including coolant circuit verification, component testing, and system performance validation for battery and motor cooling.

Warnings

Tools required

Parts

• Thermal management system coolant filter × 1 — Use OEM specification
• Coolant reservoir cap seal × 1 — Use OEM specification
• O-ring kit for thermal system quick disconnects × 1 — Use OEM specification

Fluids

• EV Battery/Motor Coolant — 10 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Verify vehicle has been stationary for minimum 2 hours to allow thermal system to cool
3. Connect diagnostic scanner and retrieve all thermal management DTCs
4. Document battery pack temperature, motor temperatures, and coolant temperatures from vehicle systems
5. Disconnect 12V battery using proper battery disconnect procedure
6. Wait 5 minutes for high voltage system capacitors to discharge
7. Verify HV system is de-energized using approved testing procedure
8. Remove underbody access panels to access thermal system components
9. Place coolant drain pan under thermal system drain points

Procedure

1. 1

   Connect diagnostic scanner and baseline system
   Connect Rivian diagnostic scanner and navigate to thermal management system module. Record baseline parameters: coolant flow rates, pump speeds, radiator fan operation, chiller operation (if applicable), and all temperature sensors. Document any active or stored DTCs related to thermal management.
2. 2

   Inspect thermal system for external leaks
   Perform visual inspection of all thermal system components including coolant reservoir, radiator assembly, battery pack cooling plates, motor cooling jackets, hoses, quick-disconnect fittings, and chiller unit. Check for evidence of coolant leaks, corrosion, or damage. Inspect electrical connections to thermal management pumps and valves for corrosion or damage.
3. 3

   Test thermal system pressure integrity
   Using coolant pressure tester, pressurize the thermal management system to 20 PSI. Monitor pressure for 10 minutes. System should not lose more than 2 PSI in 10 minutes. If pressure loss exceeds specification, use infrared camera or leak detection method to locate leak source. Document all findings.
4. 4

   Drain thermal management coolant
   Locate coolant drain valve on battery pack thermal circuit and motor thermal circuit. Open drain valves and drain coolant into appropriate container. Note coolant condition, color, and any contamination. If coolant appears contaminated or discolored, investigate for internal component degradation. Capture minimum 8 quarts for proper disposal.
5. 5

   Remove and inspect coolant filter
   Locate thermal system coolant filter assembly (typically mounted near battery pack underbody). Remove filter housing bolts and carefully extract filter element. Inspect filter for debris, metal particles, or excessive contamination. Replace filter with new OEM-specified unit. Inspect housing O-rings and replace if worn or damaged.
6. 6

   Test thermal management pumps
   Using diagnostic scanner, command each thermal management pump to operate independently. Verify pump operation by listening for pump activation and monitoring commanded vs actual pump speed. Battery cooling pump and motor cooling pump should reach commanded speeds within 5 seconds. Check pump electrical draw using multimeter - typical draw is 3-8 amps depending on speed.
7. 7

   Inspect and test thermal control valves
   Using diagnostic scanner, actuate each thermal control valve (coolant routing valves, bypass valves, chiller integration valves). Verify valve position feedback matches commanded position. Inspect valve bodies for leaks or damage. Test valve electrical circuits for proper resistance values per manufacturer specifications (typically 10-50 ohms depending on valve type).
8. 8

   Test temperature sensors
   Using multimeter, test resistance values of all thermal system temperature sensors: battery inlet/outlet, motor inlet/outlet, radiator inlet/outlet, and ambient temperature sensor. Compare readings to manufacturer specifications for current ambient temperature. Typical NTC sensors read 2000-3000 ohms at 77°F. Replace any sensors reading out of specification or showing erratic values.
9. 9

   Inspect battery pack thermal interface
   If accessible without full pack removal, inspect battery pack cooling plate connections and thermal interface material condition. Check quick-disconnect fittings for proper sealing and O-ring condition. Verify mounting brackets and vibration isolators are intact. Look for signs of coolant weeping at pack interface points.
10. 10

    Refill thermal management system
    Using approved EV Battery/Motor Coolant, refill thermal system through designated fill port at coolant reservoir. Fill slowly to prevent air pocket formation. Add coolant until system capacity reaches 10 quarts. Do not overfill. Install new reservoir cap with fresh seal to ensure proper pressure maintenance.
11. 11

    Bleed thermal system and purge air
    Using diagnostic scanner, activate thermal system bleed procedure. This will cycle pumps and open valves in sequence to purge air from system. Monitor coolant level and add as needed during bleeding process. Continue until no air bubbles are observed in coolant reservoir and coolant level stabilizes. Process typically takes 15-20 minutes.
12. 12

    Perform thermal system functional test
    With diagnostic scanner connected, activate thermal management system self-test routine. System will cycle all pumps, valves, and fans through operational ranges. Monitor for proper flow rates (typically 8-15 liters/minute depending on circuit), temperature differentials across components (should be 5-15°F across battery pack and 10-25°F across motors under load), and verify no leaks develop during pressurized operation.
13. 13

    Verify thermal protection systems
    Using diagnostic scanner, verify all thermal protection thresholds are properly configured: battery over-temperature shutdown (typically 140-150°F), motor over-temperature derate (typically 350-375°F), and coolant over-temperature warnings (typically 190-200°F). Confirm all protection systems are active and responding to simulated fault conditions.

Reassembly

1. Reinstall all underbody access panels and thermal system covers
2. Ensure all electrical connectors are fully seated and locked
3. Verify all coolant system connections are tight and properly secured
4. Reconnect 12V battery following manufacturer procedure
5. Clear any diagnostic trouble codes related to battery disconnect or service mode

Verification

• With scanner connected, verify no thermal management DTCs are present
• Start vehicle and allow thermal system to reach operating temperature (approximately 15-20 minutes)
• Using infrared thermometer, verify temperature uniformity across battery pack (should be within 10°F variation)
• Verify motor temperatures are being properly regulated during light operation
• Check coolant level after thermal cycling and top off if needed (should remain stable)
• Perform test drive with scanner monitoring thermal parameters - verify coolant flow increases with power demand
• Verify all thermal management components respond properly to load changes during acceleration and regenerative braking
• Confirm battery pack maintains temperature within 60-110°F range during normal operation
• Verify no coolant leaks are present after thermal cycling
• Document all final temperature readings and system parameters for customer records

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