GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC P42 Commercial Chassis 🢒 Engine 🢒 Engine Cooling 🢒 Coolant Heater Replacement

Removal Procedure

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable.
  2. Drain the coolant. Refer to Cooling System Draining and Filling .
  3. Remove the heat shield, if equipped.
  4. Disconnect the electrical cord connector from the engine coolant heater.
  5. Loosen the center screw to the limit of the thread.

    6. Object Number: 204539 Size: SH
  6. Remove the engine coolant heater from the engine block.
  7. Inspect the hole in the block for smoothness. Remove any burrs or rough spots.

Installation Procedure

    Object Number: 204565 Size: SH
  1. Apply a coat of petroleum jelly to the heater opening and the O-ring.
  2. Insert the engine coolant heater into the hole in the engine block.

    3. Object Number: 341276 Size: SH
  3. Position the hairpin end of the engine coolant heater toward the front of the vehicle.

    4. 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.

  4. Tighten the engine cooler heater center screw.

    5. Tighten
    Tighten the engine coolant heater center screw to 3 N·m (23 lb in).

  5. Install the heat shield, if equipped.

    6. Tighten
    Tighten the heat shield bolt to 12 N·m (106 lb in).

    Notice: The heater cord must not touch the engine, hot pipes, manifold, or any moving parts. Route the cord to the left front of the engine compartment securing with tie straps as necessary to prevent damage.

  6. Connect the electrical cord connector to the engine coolant heater.
  7. Fill the cooling system. Refer to Cooling System Draining and Filling .
  8. Inspect the system for leaks.

    9. Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  9. Connect the negative battery cable.