Thermostat Housing Crossover Replacement 6.6L (LB7) Engine

1. Disconnect the battery negative cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
2. Drain the engine coolant. Refer to Cooling System Draining and Filling .
3. Remove the upper fan shroud. Refer to Fan Shroud Replacement .
4. Remove the drive belt. Refer to Drive Belt Replacement in Engine Mechanical - 6.6L.



5. Disconnect the A/C compressor clutch electrical connector.
6. Disconnect the A/C cut out switch electrical connector.
7. Remove the A/C compressor mounting bolts.
8. Move the A/C compressor with the hoses attached to the right side of the engine compartment.



9. Remove the nut retaining the generator positive cable to the generator.
10. Remove the positive cable from the generator.
11. Remove the clip holding the positive cable to the engine front cover.
12. Remove the bolt retaining the battery positive cable junction block to the power steering pump.
13. Move the generator positive cable and the junction block bracket aside.
14. Disconnect the generator electrical connector.
15. Disconnect the engine coolant temperature (ECT) sensor electrical connector.



16. Remove the power steering pump mounting bracket and secure to the side. Refer to Air Conditioning (A/C) Compressor and Power Steering Pump Bracket Replacement .

•	Do not remove the power steering pump from the bracket.

•	The hoses and battery cables can remain on the power steering pump.




17. Remove the bolts retaining the fuel bleed valve and PCV oil separator bracket from the generator mounting bracket.



18. Remove the heater outlet hose bracket bolt from the generator bracket.
19. Remove the ribbed idler pulley.
20. Remove the generator mounting bracket and secure to the side.

•	The generator does not require removal.

•	The drive belt tensioner does not require removal.

21. Remove the oil fill tube. Refer to Oil Filler Tube Replacement in Engine Mechanical - 6.6L.
22. Remove the water outlet tube. Refer to Water Outlet Tube Replacement .



23. Remove the bolt retaining the heater pipe to the fuel filter assembly.
24. Remove the bolt retaining the heater pipe to the thermostat housing crossover.
25. Remove the heater pipe with O-ring seal from the crossover.



26. Remove the hose and clamp from the turbocharger outlet coolant pipe to thermostat bypass pipe.
27. Remove the fuel line bracket from the thermostat housing crossover.
28. Remove the cooling fan pulley. Refer to Cooling Fan Pulley Replacement .



29. Remove the 2  thermostat housing crossover bolts and 2 nuts from the left cylinder head.
30. Remove the 2 thermostat housing crossover bolts and 2 nuts from the right cylinder head.
31. Remove the bypass pipe to water pump bolts.
32. Remove the thermostat housing crossover with the bypass pipe.
33. Remove the bypass pipe to water pump O-ring.



34. Remove the bypass pipe from the thermostat housing crossover.
35. Remove the O-ring from the bypass pipe.

1. If required, remove the thermostat cover bolts.
2. Remove the thermostat cover.
3. Remove the thermostats with seals.
4. Remove the thermostat seals.
5. Remove the ECT sensor if replacing the thermostat housing crossover.



6. Clean the water crossover.
7. Clean the thermostat housing crossover mating surfaces.
8. Inspect the thermostat housing crossover for cracks.
9. Inspect the thermostat housing crossover mating surfaces for damage.
10. Replace the thermostat housing crossover if any damage is found.



11. Install the thermostats with the seals.

The thermostat with the vent valves goes toward the rear of the engine. Install with the vent valves towards the rear of the engine.

12. Install the thermostat cover and gasket.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

13. Install the thermostat cover bolts.

Tighten
Tighten the thermostat cover bolts to 21 N·m (15 lb ft).

14. If removed, install the ECT sensor.

Tighten
Tighten the ECT sensor to 33 N·m (24 lb ft).

1. Install a new O-ring to the bypass pipe. Lubricate the O-ring with coolant.
2. Install the bypass pipe to the thermostat housing crossover.



3. Install new thermostat crossover gaskets.
4. Install a new O-ring for the bypass pipe to the water pump.
5. Install the thermostat crossover with the bypass pipe.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

6. Install the bypass pipe to water pump bolts.

Tighten
Tighten the bypass pipe to water pump bolts to 21 N·m (15 lb ft).

7. Install the thermostat crossover bolts and nuts.

Tighten
Tighten the thermostat crossover bolts and nuts to 21 N·m (15 lb ft).

8. Install the fuel line bracket and bolt.

Tighten
Tighten the fuel line bracket bolt to 21 N·m (15 lb ft).




9. Install the hose and clamp from the turbocharger outlet coolant pipe to thermostat bypass pipe.
10. Install the cooling fan pulley. Refer to Cooling Fan Pulley Replacement .



11. Install a new O-ring seal to the heater pipe.
12. Install the heater pipe to the thermostat housing crossover.
13. Install the bolt retaining the heater pipe to the thermostat housing crossover.

Tighten
Tighten the heater pipe bolt to 21 N·m (15 lb ft).

14. Install the bolt retaining the heater pipe to the fuel filter assembly.

Tighten
Tighten the heater pipe bracket bolt to 21 N·m (15 lb ft).




15. Install the generator mounting bracket and bolts.

Tighten
Tighten the generator mounting bracket bolts to 50 N·m (37 lb ft).

16. Install the ribbed idler pulley and the bolt.

Tighten
Tighten the idler puller bolt to 43 N·m (32 lb ft).

17. Install the heater outlet hose bracket bolt.

Tighten
Tighten the bracket bolt to 21 N·m (15 lb ft).




18. Install the nuts retaining the fuel bleed valve and PCV oil separator bracket from the generator mounting bracket.

Tighten
Tighten the bracket nuts to 25 N·m (18 lb ft).




19. Install the power steering pump mounting bracket and bolts. Refer to Air Conditioning (A/C) Compressor and Power Steering Pump Bracket Replacement .

Tighten
Tighten the power steering pump mounting bracket bolts to 46 N·m (34 lb ft).

20. Install the water outlet tube. Refer to Water Outlet Tube Replacement .



21. Position the generator positive cable.
22. Install the generator positive cable in the clip on the engine front cover.
23. Install the generator positive cable and the retaining nut to the generator.

Tighten
Tighten the generator positive cable nut to 9 N·m (80 lb in).

24. Install the battery positive cable junction block bracket and bolt to the power steering pump.

Tighten
Tighten the junction block bracket bolt to 9 N·m (80 lb in).

25. Connect the generator electrical connector.



26. Position the A/C compressor.
27. Install the A/C compressor mounting bolts.

Tighten
Tighten the A/C compressor mounting bolts to 50 N·m (37 lb ft).

28. Connect the A/C cut out switch electrical connector.
29. Connect the A/C clutch electrical connector.
30. Install the drive belt. Refer to Drive Belt Replacement in Engine Mechanical - 6.6L.
31. Install the upper fan shroud. Refer to Fan Shroud Replacement .
32. Fill the engine coolant. Refer to Cooling System Draining and Filling .
33. Connect the battery negative cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.