EV Coolant Lines

This procedure covers the removal and replacement of the EV coolant lines that circulate coolant through the battery thermal management system and electric drive unit on the 2023 Chevrolet Bolt EUV.

Warnings

Tools required

Parts

• EV coolant line assembly × 1 — Use OEM specification
• Coolant line O-rings × 4 — Use OEM specification
• Hose clamps × 2 — Use OEM specification
• Coolant line retaining clips × 3 — Use OEM specification

Fluids

• ACDelco DEX-COOL (Orange) — 2 qt

Preparation

1. Park vehicle on level ground and apply parking brake. Place wheel chocks behind rear wheels.
2. Ensure vehicle has been off and cooling for at least 2 hours.
3. Disconnect 12V auxiliary battery negative terminal and wait 5 minutes.
4. Remove high voltage service disconnect located under rear seat bottom cushion. Store disconnect plug in your pocket to prevent accidental reconnection.
5. Raise and support vehicle on jack stands at manufacturer-specified lift points.
6. Remove front driver side wheel to access underbody coolant lines.
7. Remove underbody splash shield using plastic trim tools and 10mm socket.
8. Place drain pan under coolant reservoir and slowly remove reservoir cap to relieve any residual pressure.
9. Identify which coolant lines require replacement and trace their routing from drive unit to radiator/heater.

Procedure

1. 1

   Drain EV coolant system
   Locate the coolant drain plug on the bottom of the EV coolant reservoir. Position drain pan underneath and remove the drain plug. Allow coolant to drain completely, which may take 10-15 minutes. If replacing lines connected to the battery cooling system, also drain the battery coolant loop using the secondary drain point near the battery pack.
2. 2

   Disconnect electrical connectors from coolant sensors
   Locate the coolant temperature sensors mounted on the coolant lines near the drive unit. Press the locking tabs and disconnect the electrical connectors. If sensors are being reused, leave them installed in the old lines for now. Note the orientation and position of each connector for reassembly.
3. 3

   Remove coolant line mounting brackets
   Using a 12mm socket, remove the mounting brackets that secure the coolant lines to the vehicle chassis and drive unit mounting points. There are typically 3-4 brackets along the line routing. Keep track of bracket positions as they must be reinstalled in the same locations to prevent vibration and chafing.
   Torque spec

   Bracket Bolts20 Nm (15 lb-ft)
4. 4

   Disconnect coolant lines from drive unit
   Locate the quick-connect fittings or threaded fittings where coolant lines connect to the electric drive unit. For quick-connect fittings, press the release tabs and pull the line straight out. For threaded fittings, use a 14mm wrench to loosen the coolant line fittings. Have shop towels ready as residual coolant will drain from the lines. Inspect the O-rings and replace if damaged.
   ⚠Do not twist or bend coolant lines excessively during removal as this can damage internal sealing surfaces.
5. 5

   Disconnect coolant lines from heater core and radiator
   Follow the coolant lines to their connection points at the heater core inlet/outlet and EV coolant radiator. Release hose clamps using hose clamp pliers or a flat-blade screwdriver. Twist hoses gently to break the seal, then pull straight off the fittings. If lines have threaded connections at the radiator, use appropriate wrench to disconnect.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
6. 6

   Remove coolant line retaining clips
   Along the coolant line routing, there are plastic retaining clips that hold the lines to the chassis and other components. Using a flat-blade screwdriver or trim tool, carefully pry these clips out of their mounting holes. Keep clips organized for reinstallation or replacement if damaged.
7. 7

   Remove old coolant lines
   Carefully maneuver the coolant line assembly out from the engine bay, being mindful of sharp edges and other components. Note the exact routing path, taking photos if necessary, as the new lines must follow the same path. Check for any additional clips or fasteners that may have been missed.
8. 8

   Prepare new coolant lines
   Unpack new coolant line assembly and compare to old lines to verify correct part. Install new O-rings on all threaded fittings, lubricating them lightly with fresh DEX-COOL coolant. Ensure all quick-connect fittings have new O-rings and retaining clips installed. Inspect all connection points for debris or damage.
9. 9

   Route and position new coolant lines
   Following the routing path documented during removal, carefully position the new coolant line assembly in the vehicle. Ensure lines do not contact sharp edges, moving components, or hot surfaces. Verify that all mounting bracket locations align with chassis mounting points before making any connections.
   ⚠Ensure coolant lines have adequate clearance from drive axles and suspension components throughout their full range of motion.
10. 10

    Connect coolant lines to drive unit
    Connect the coolant lines to the electric drive unit. For quick-connect fittings, push firmly until you hear/feel a click and verify the locking tabs are engaged. For threaded fittings, thread by hand first to prevent cross-threading, then tighten to specification using a torque wrench. Verify O-rings are properly seated.
    Torque spec

    Coolant Line Fittings15 Nm (11 lb-ft)
11. 11

    Connect coolant lines to radiator and heater core
    Attach coolant lines to the radiator and heater core connections. Push hoses fully onto fittings until they bottom out. Install new hose clamps and position them approximately 1/4 inch from the end of the hose. Tighten clamps to specification, ensuring even pressure around the circumference.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
12. 12

    Install mounting brackets and retaining clips
    Reinstall all coolant line mounting brackets in their original positions. Tighten bracket bolts to specification. Install all retaining clips along the line routing, ensuring lines are properly secured but not over-tightened or kinked. Verify adequate clearance from all moving and hot components.
    Torque spec

    Bracket Bolts20 Nm (15 lb-ft)
13. 13

    Reconnect coolant temperature sensors
    If coolant temperature sensors were removed from old lines, transfer them to the new lines and tighten to specification. Reconnect all electrical connectors to the coolant sensors, ensuring locking tabs click into place. Verify connectors are fully seated and secure.
    Torque spec

    Sensor Bolts11 Nm (8 lb-ft)
14. 14

    Refill coolant system
    Close the coolant drain plug. Using a coolant funnel with adapter, slowly refill the EV coolant reservoir with fresh ACDelco DEX-COOL (orange) coolant. Fill to the COLD FILL line on the reservoir. If both coolant loops were drained, refill both reservoirs. Allow coolant to settle for 5 minutes and top off as needed.
15. 15

    Bleed cooling system
    With the coolant reservoir cap still off, reinstall the high voltage service disconnect and reconnect the 12V battery. Turn the vehicle to ON mode (do not enter READY mode). Activate the electric climate control to MAX heat and high fan speed. Allow the coolant pump to circulate for 10 minutes while monitoring coolant level. Add coolant as air is purged from the system. The coolant level will drop as air is expelled. Once level stabilizes and no more bubbles appear, install the reservoir cap.
    ⚠Monitor for coolant leaks during the bleeding process. Immediately turn off the vehicle if any leaks are observed.

Reassembly

1. Reinstall underbody splash shield and torque fasteners to specification.
2. Reinstall front driver side wheel and torque lug nuts to manufacturer specification (140 Nm / 103 lb-ft).
3. Lower vehicle from jack stands.
4. Verify all electrical connectors are properly seated and locked.
5. Clean up any spilled coolant from engine bay and undercarriage.

Verification

• With vehicle in READY mode, verify the coolant temperature gauge shows normal operating temperature after a 10-minute test drive.
• Check for coolant leaks at all connection points including drive unit fittings, radiator connections, and heater core connections while engine is at operating temperature.
• Verify coolant level in reservoir is between MIN and MAX marks when vehicle is cold.
• Confirm no warning lights are illuminated on the instrument cluster, particularly the coolant temperature warning or propulsion system warning.
• Test heater operation by setting climate control to maximum heat and verifying hot air output.
• Scan for diagnostic trouble codes using a compatible scan tool to ensure no cooling system faults are present.
• Perform a final walk-around inspection under the vehicle after 24 hours of normal driving to check for delayed leaks.

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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