Heater Control Valve

Replace the heater control valve that regulates coolant flow to the heater core on the 5.9L Cummins diesel engine.

Warnings

Tools required

Parts

• Heater control valve × 1 — Use OEM specification
• Hose clamps × 2 — Worm-gear or spring-type per factory spec
• Coolant 50/50 mix × 2 — Green conventional (pre-2001) or HOAT (2001+)

Fluids

• Ethylene glycol 50/50 (green conventional early, HOAT later) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Place drain pan under radiator and heater hose area
3. Locate heater control valve on engine firewall, passenger side near heater hoses
4. Take photo of vacuum line routing to heater control valve for reference during reinstallation

Procedure

1. 1

   Drain coolant from system
   Open the radiator drain petcock at the bottom of the radiator and drain enough coolant (approximately 2-3 gallons) into the drain pan to lower the coolant level below the heater hoses and minimize spillage. Close the petcock when finished draining.
   Torque spec

   Drain Petcock7 Nm (5 lb-ft)
2. 2

   Disconnect vacuum line
   Carefully pull the vacuum line off the heater control valve actuator. Note the orientation and routing of this line. The vacuum line controls valve operation and must be reinstalled correctly.
3. 3

   Remove inlet hose clamp
   Using pliers or hose clamp tool, loosen and remove the hose clamp securing the inlet heater hose to the heater control valve. The inlet is typically the upper connection coming from the engine.
4. 4

   Remove outlet hose clamp
   Loosen and remove the hose clamp securing the outlet heater hose to the heater control valve. The outlet typically runs toward the heater core on the firewall.
5. 5

   Remove heater hoses
   Twist and pull both heater hoses off the valve connections. Residual coolant will drain from the hoses and valve. Keep drain pan positioned to catch spillage. Inspect hose ends for cracking or deterioration.
6. 6

   Remove valve mounting hardware
   Remove the mounting bracket bolt or screw securing the heater control valve to the firewall or engine mounting point. Note the orientation of the valve and any mounting brackets for correct reinstallation.
   Torque spec

   Valve Mounting8 Nm (6 lb-ft)
7. 7

   Remove heater control valve
   Pull the heater control valve away from the mounting location. Inspect the old valve for failure mode (stuck open, stuck closed, or leaking) to confirm diagnosis.
8. 8

   Prepare new valve
   Compare new heater control valve to old unit to verify correct replacement. Check that vacuum actuator moves freely and valve opens and closes smoothly. Clean heater hose connection points with shop towel or wire brush to remove old coolant residue.
9. 9

   Install new valve
   Position new heater control valve in mounting location with vacuum actuator oriented correctly (reference photo taken during disassembly). Install mounting bolt or screw and torque to specification.
   Torque spec

   Valve Mounting8 Nm (6 lb-ft)
10. 10

    Connect heater hoses
    Push inlet and outlet heater hoses firmly onto the valve connections until they seat completely. Ensure hoses are routed without kinks and not contacting sharp edges or hot exhaust components.
11. 11

    Install hose clamps
    Install new hose clamps on both inlet and outlet hose connections. Position clamps at least 1/4 inch from hose ends. Tighten worm-gear clamps snugly with a screwdriver or nut driver; spring-type clamps simply seat into position.
    Torque spec

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

    Reconnect vacuum line
    Push vacuum line firmly onto heater control valve actuator nipple until fully seated. Verify vacuum line routing matches photo reference and does not contact hot or moving components.
13. 13

    Refill cooling system
    Add coolant mixture to radiator and overflow reservoir to proper levels. Use correct coolant type for model year per factory specification: green conventional ethylene glycol for earlier models and HOAT (Chrysler G-05) for later models; verify the exact cutover year for your specific vehicle. Fill radiator to neck and overflow to FULL COLD mark.
14. 14

    Bleed air from system
    With radiator cap off, start engine and allow to idle. Turn heater controls to maximum heat and fan speed. Watch coolant level and add as needed while engine warms. Air bubbles will rise to radiator opening. Run until thermostat opens and upper radiator hose becomes hot, then turn off engine.
15. 15

    Final coolant level adjustment
    After engine cools, recheck coolant level in radiator and overflow reservoir. Top off as needed to proper levels. Install radiator cap securely.

Reassembly

1. Double-check all hose clamps are properly tightened to prevent coolant leaks
2. Verify vacuum line is securely connected and properly routed away from heat sources
3. Confirm coolant level is at proper FULL COLD mark on overflow reservoir

Verification

• Start engine and verify no coolant leaks around heater control valve or hose connections
• Turn heater control to maximum heat and verify hot air comes from vents within 5 minutes of engine warmup
• Turn heater control to off or A/C mode and verify heater output stops or reduces significantly, confirming valve operation
• Monitor coolant level over next few days and top off as air continues to purge from system
• Check for proper heater performance during test drive after engine reaches operating temperature

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