GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Pickup - 4WD 🢒 Engine 🢒 Engine Cooling 🢒 Coolant Heater Replacement

Removal Procedure
  1. Drain the engine coolant. Refer to Cooling System Draining and Filling .

    2. Object Number: 312953 Size: SH
  2. Remove the heater cord from the engine coolant heater (2).
  3. Loosen the bolt retaining the engine coolant heater to the block.
  4. Remove the engine coolant heater from the engine block.
  5. If the vehicle is not originally equipped with an engine coolant heater, remove the coolant jacket plug.
  6. Carefully tap the coolant plug near the outer edge.
  7. Rotate the coolant plug out of the core plug hole.

    8. Do not score the machined surface of the hole.

  8. Grasp the plug with pliers.
  9. Pull the plug from the engine block.
  10. Clean the core plug hole in order to remove the following substances:
    11. • Burrs
    • Compound
    • Paint
    • Rough spots

Installation Procedure

    Object Number: 312935 Size: SH
  1. Coat the o-ring seal (2) and the cleaned surface of the plug opening with water resistant high-temperature grease lubricant GM P/N 9985164 or the equivalent.

    2. Important: Avoid element contact with the inside walls of the engine block.

  2. Install the coolant heater by pushing tightly into the engine block.

    3. Object Number: 312945 Size: SH

    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. Tighten the bolt on the engine coolant heater until both of the locking wings draw tightly against the inner wall of the engine block.

    4. Tighten
    Tighten the bolt in order to retain the engine coolant heater to the engine block to 2 N·m (18 lb in).

    Important: Do not allow the heater cord to touch the following areas:

       • The engine
       • Hot pipes
       • The manifold
       • Any moving parts.


    Object Number: 312953 Size: SH
  4. Install the heater cord to the coolant heater (2).
  5. Route the heater cord.
  6. Fill the radiator and the engine with engine coolant. Refer to Cooling System Draining and Filling .
  7. Inspect the system for leaks.