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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Cooling 🢒 Engine Coolant Thermostat Replacement

Engine Coolant Thermostat Replacement Caterpillar

Refer to the Caterpillar® Service Manual.

Engine Coolant Thermostat Replacement 8.1L Engine

Removal Procedure

    Object Number: 751425 Size: SH
  1. Drain the cooling system. Refer to Cooling System Draining and Filling .
  2. Reposition the inlet hose clamp at the water outlet.
  3. Remove the inlet hose from the water outlet.

    4. Object Number: 635643 Size: SH
  4. Remove the water outlet bolts (2).
  5. Remove the water outlet (1).
  6. Remove the thermostat (3).

Installation Procedure

    Object Number: 635643 Size: SH
  1. Install the thermostat (3).
  2. Install the water outlet (1).

    3. 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.

  3. Install the water outlet bolts (2).

    4. Tighten
    Tighten the bolts to 30 N·m (22 lb ft).


    Object Number: 751425 Size: SH
  4. Install the inlet hose to the water outlet.
  5. Position the inlet hose clamp at the water outlet.
  6. Fill the cooling system. Refer to Cooling System Draining and Filling .

Engine Coolant Thermostat Replacement LG4

Removal Procedure
  1. Drain the coolant. Refer to Cooling System Draining and Filling .
  2. Remove the upper radiator hose from the coolant outlet.

    3. Object Number: 228201 Size: SH
  3. Remove the coolant outlet bolts.
  4. Remove the coolant outlet (1).
  5. Remove the thermostats (2).
  6. Clean the following surfaces:
    7. • The inlet manifold
    • The coolant outlet
  7. Inspect the coolant outlet for the following conditions:
    8. • Flat mating surfaces
    • Pits
    • Cracks
    • Other damage

Installation Procedure

    Object Number: 228198 Size: SH

    Important: Place the thermostat with the jiggle valves on the left side.

  1. Install the thermostats.

    2. Object Number: 228201 Size: SH
  2. Install the coolant outlet (1).

    3. Notice: Refer to Fastener Notice in the Preface section.

  3. Install the coolant outlet bolts.

    4. Tighten
    Tighten the coolant outlet bolts to 19 N·m (14 lb ft).

  4. Install the upper radiator hose to the coolant outlet.

    5. Tighten
    Tighten the clamp to 5 N·m (44 lb in).

  5. Fill the cooling system. Refer to Cooling System Draining and Filling .
  6. Inspect the system for leaks.

Engine Coolant Thermostat Replacement 6.6L LLY

Removal Procedure

  1. Remove the air cleaner . Refer to Air Cleaner Replacement for the 6.6L (LLY) engine.
  2. Remove the charged air cooler pipes. Refer to Charged Air Cooler Hoses/Pipes Replacement .

    3. Object Number: 660424 Size: SH
  3. Remove the water outlet. Refer to Water Outlet Tube Replacement .
  4. Remove the bolt for the fuel line bracket.
  5. Remove the thermostat housing cover bolts.
  6. Remove the thermostats and seals.

Inspection Procedure
  1. Inspect the thermostats for sticking, cracks, and/or leakage of wax. Refer to Thermostat Diagnosis .
  2. Replace the thermostats if damage is found.
  3. Clean the thermostat housing and thermostat housing cover sealing surfaces.

Installation Procedure

    Object Number: 654534 Size: SH
  1. Install the thermostats and seals to the thermostat housing.

    2. The rear thermostat (4) has 2 vent valves. Install with the vent valves towards the rear of engine.

    Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 660424 Size: SH
  2. Install the thermostat housing cover.
  3. Install the thermostat housing cover bolts.

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

  4. Install the fuel line bracket bolt.

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

  5. Install the water outlet. Refer to Water Outlet Tube Replacement .
  6. Install the charged air cooler pipes. Refer to Charged Air Cooler Hoses/Pipes Replacement .
  7. Install the air cleaner . Refer to Air Cleaner Replacement for the 6.6L (LLY) engine.

Engine Coolant Thermostat Replacement 6.6L LMM

Removal Procedure


    Object Number: 1869833 Size: SH
  1. Remove the air cleaner. Refer to Air Cleaner Assembly Replacement .
  2. Remove the water outlet. Refer to Water Outlet Tube Replacement .
  3. Remove the cooling fan shroud top bracket bolts.

    4. Object Number: 1869838 Size: SH
  4. Remove the thermostat housing cover bolts.
  5. Remove the thermostats and seals.

Inspection Procedure
  1. Inspect the thermostats for sticking, cracks, and/or leakage of wax. Refer to Thermostat Diagnosis .
  2. Replace the thermostats if damage is found.
  3. Clean the thermostat housing and thermostat housing cover sealing surfaces.

Installation Procedure

    Object Number: 654534 Size: SH
  1. Install the thermostats and seals to the thermostat housing.

    2. The rear thermostat (4) has 2 vent valves. Install with the vent valves towards the rear of engine.

    Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 1869838 Size: SH
  2. Install the thermostat housing cover.
  3. Install the thermostat housing cover bolts.

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


    Object Number: 1869833 Size: SH
  4. Install the cooling fan shroud top bracket bolts.

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

  5. Install the water outlet. Refer to Water Outlet Tube Replacement .
  6. Install the air cleaner . Refer to Air Cleaner Assembly Replacement .