Thermostat Housing

Replace the thermostat housing on the 6.7L Cummins diesel engine, including draining coolant, removing the old housing, installing a new housing with gasket, and refilling the cooling system.

Warnings

Tools required

Parts

• Thermostat housing assembly × 1 — Use OEM Mopar specification
• Thermostat housing gasket × 1 — Usually included with housing
• Coolant hose clamps (if corroded) × 2 — OEM or equivalent

Fluids

• Mopar OAT Coolant (Purple) — 2 qt

Preparation

1. Ensure engine is completely cold (at least 2 hours after last operation)
2. Park vehicle on level ground and apply parking brake
3. Disconnect negative battery cable to prevent accidental fan activation
4. Place drain pan under radiator drain plug
5. Remove engine cover by pulling upward on retaining clips

Procedure

1. 1

   Drain cooling system
   Open the radiator drain plug at the bottom of the radiator (driver side) and drain coolant into the drain pan. Once drained, close the drain plug and torque to specification. This prevents complete system drainage and reduces refill time.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)
2. 2

   Remove air intake components
   Loosen the clamp at the turbocharger inlet and remove the intake tube from the air filter housing to the turbo. This provides necessary access to the thermostat housing area on the driver side of the engine.
3. 3

   Disconnect coolant hoses
   Locate the thermostat housing on the front driver side of the engine block. Use hose clamp pliers to release the spring clamps on the upper radiator hose and bypass hose connections to the thermostat housing. Twist hoses gently to break seal, then pull off the housing nipples. Be prepared for residual coolant spillage.
4. 4

   Remove electrical connector
   Disconnect the electrical connector from the Engine Coolant Temperature (ECT) sensor mounted on the thermostat housing. Press the release tab and pull the connector straight off.
5. 5

   Remove thermostat housing bolts
   Remove the four bolts securing the thermostat housing to the engine block using the appropriate socket. Keep bolts organized for reinstallation. Note the bolt locations as they may be different lengths.
6. 6

   Remove thermostat housing
   Carefully pull the thermostat housing away from the engine block. It may be stuck due to the gasket seal. Use a small pry bar if necessary, but be extremely careful not to damage the mating surface on the engine block. Remove the old gasket completely.
   ⚠Do not pry against the engine block mating surface. Any scratches or gouges will cause coolant leaks.
7. 7

   Clean mating surfaces
   Use a gasket scraper or plastic scraper to remove all old gasket material from the engine block mating surface. The surface must be completely clean and smooth with no residue, corrosion, or scratches. Wipe clean with a shop rag and inspect carefully.
8. 8

   Install new gasket and housing
   Position the new gasket onto the engine block mounting surface, aligning all bolt holes. Place the new thermostat housing against the gasket, ensuring proper alignment. Start all four mounting bolts by hand to ensure proper threading before tightening any bolts.
9. 9

   Torque housing bolts
   Tighten the thermostat housing bolts in a criss-cross pattern to specification using a torque wrench. This ensures even gasket compression and prevents warping or leaks.
   Torque spec

   Housing Bolts18 Nm (14 lb-ft)
10. 10

    Reconnect coolant hoses
    Reinstall the upper radiator hose and bypass hose onto the new thermostat housing nipples. Ensure hoses are fully seated onto the nipples. Position the spring clamps or install new clamps if originals are corroded.
    Torque spec

    Coolant Hose Clamps5 Nm (4 lb-ft)
11. 11

    Reconnect electrical connector
    Plug the ECT sensor electrical connector back onto the sensor on the thermostat housing. Ensure the connector clicks into place and is fully seated.
12. 12

    Reinstall air intake
    Reinstall the intake tube from the air filter housing to the turbocharger inlet. Ensure proper seating and tighten the clamp at the turbo inlet securely.
13. 13

    Refill cooling system
    Using the coolant overflow tank, slowly add Mopar OAT (purple) coolant until the system is full. Fill to the COLD line on the overflow tank. Start the engine and allow it to reach operating temperature with the cap off the overflow tank. Add coolant as needed as air bleeds from the system. The 6.7L Cummins is self-bleeding.
    ⚠Only use Mopar OAT purple coolant. Other coolant types will damage the system.
14. 14

    Check for leaks and top off
    With engine at operating temperature, carefully inspect all connections at the thermostat housing for coolant leaks. Check that the upper radiator hose becomes hot, indicating proper thermostat operation. Turn engine off, allow to cool slightly, and top off coolant to the COLD line. Install overflow tank cap.

Reassembly

1. Reinstall engine cover by aligning clips and pressing down firmly until seated
2. Reconnect negative battery cable
3. Properly dispose of old coolant at an approved recycling facility

Verification

• Start engine and verify no coolant leaks at thermostat housing connections
• Verify upper radiator hose becomes hot after engine reaches operating temperature, confirming thermostat operation
• Check coolant level after first drive cycle and top off if necessary
• Verify no check engine light or temperature warning lights are illuminated
• Monitor coolant level and temperature gauge for the next several days to ensure proper system operation

Related trouble codes on this vehicle

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

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle