Heater Core Replacement Procedures

2004 Chevrolet Blazer
____________

2004 Chevrolet Blazer Xtreme

Before you start removing your vehicle components, be sure you have your new heater core, heater hoses, clamps, coolant, and all other parts you will need for the job. Once you begin, you will not be able to drive the vehicle until the job is completed.

The following procedures are derived from repair procedures on the AutoZone website. Much more information to help you maintain your vehicle is available on the AutoZone website.

Warnings & Precautions

Before servicing the vehicle, please be sure to read all of the following precautions, which deal with personal safety, prevention of component damage, and important points to take into consideration when servicing a motor vehicle:

  • Never open, service or drain the radiator or cooling system when the engine is hot; serious burns can occur from the steam and hot coolant.
  • All new vehicles are now equipped with an air bag system, often referred to as a Supplemental Restraint System (SRS) or Supplemental Inflatable Restraint (SIR) system. The system must be disabled before performing service on or around system components, steering column, instrument panel components, wiring and sensors. Failure to follow safety and disabling procedures could result in accidental air bag deployment, possible personal injury and unnecessary system repairs.
  • Always wear safety goggles when working with, or around, the air bag system. When carrying a non-deployed air bag, be sure the bag and trim cover are pointed away from your body. When placing a non-deployed air bag on a work surface, always face the bag and trim cover upward, away from the surface. This will reduce the motion of the module if it is accidentally deployed. 
  • Disconnecting the negative battery cable on some vehicles may interfere with the functions of the on-board computer system(s) and may require the computer to undergo a relearning process once the negative battery cable is reconnected.
  • Only an MVAC-trained, EPA-certified automotive technician should service the air conditioning system or its components.

Heater Core Removal
1.  Before servicing the vehicle, refer to the Precautions above.

2.  Drain the engine cooling system.

3.  Remove or disconnect the following: 

   a.   Negative battery cable
 
   b.   Heater hoses from the heater core
 

 

4.  Remove the instrument panel as follows:

  1. Disable the air bag system.
    2.  
  2. Set the parking brake and block the wheels.
    3.  
  3. Disconnect the parking brake release cable from the parking brake lever.
    4.  
  4. Unfasten the screws that retain the DLC instrument panel left side sound insulator. Feed the DLC through the hole in the sound insulator.
    5.  
  5. Unfasten the right side sound insulator panel screws and remove the panel.
    6.  
  6. Unfasten the screws that attach the instrument panel left side sound insulator to the knee bolster and cowl panel.
    7.  
  7. Unfasten the nut that attaches the left side sound insulator to the accelerator pedal bracket.
    8.  
  8. Unplug the remote control door lock receiver module electrical connector.
    9.  
  9. Remove the door lock receiver module from the left side sound insulator. Remove the left side sound insulator.
    10.  
  10. Unfasten the screws that attach the instrument panel center sound insulator to the knee bolster, instrument panel, heater assembly and floor duct.
    11.  
  11. Remove the center sound insulator.
    12.  
  12. Unfasten the screws that attach the courtesy lamp to the knee bolster.
    13.  
  13. Unfasten the screws that attach the knee bolster to the instrument panel.
    14.  
  14. Disconnect the lap cooler duct from the knee bolster.
    15.  
  15. Unplug the lighter electrical connection and remove the knee bolster.
    16.  
  16. Unfasten the steering column-to-instrument panel nuts and lower the column.
    17.  
  17. Unfasten the screws that attach the instrument panel accessory trim plate to the instrument panel.
    18.  
  18. Remove the trim plate and unplug all necessary electrical connection.
    19.  
  19. Remove the heater and/or air conditioning control assembly.
    20.  
  20. Remove the radio and the storage compartment assembly (if equipped).
    21.  
  21. If necessary, remove the instrument cluster.
    22.  
  22. Unfasten the left and right instrument panel pivot bolts and the panel lower support bolt.
    23.  
  23. Unfasten the speaker grilles retaining screws and remove the speaker grilles.
    24.  
  24. Remove the windshield defroster grille using a flat-bladed prytool. Start at one end of the grille and work your way down the grille.
    25.  
  25. Unfasten the 4 instrument panel upper support screws.
    26.  
  26. Tag and unplug all necessary electrical connections.
    27.  
  27. Remove the instrument panel from the vehicle.
    28.  

5.  Remove or disconnect the following: 

a.  Air inlet assembly, if equipped

b.  Vacuum hoses

c.  Heater assembly studs, from inside the engine compartment

d.  Blower motor resistor

e.   Stud from inside the heater case assembly  (the stud is located behind the blower motor resistor)

f.  Heater assembly-to-chassis screws

g.  Heater assembly from the vehicle
Fig 1. Heater Case Assembly - small.jpg

h.  Access cover screws and cover from the heater assembly
Heater Case Cover - small.jpg

i.  Heater core from the heater case assembly 
Heater Core - small.jpg

 

Heater Core Installation:

1.  Install or connect the following: 

a.  Heater core to the heater case assembly
Heater Core Mounting - small.jpg
 
b.  Access cover to the heater assembly and the cover screws
 
c.  Heater assembly to the vehicle
 
d.  Heater assembly-to-chassis screws and torque them to 40 inch lbs. (4.5 Nm)
 
e.  Stud, working from inside the heater case assembly; the stud is located behind the blower motor resistor
 
f.  Blower motor resistor
 
g. Heater assembly studs, working inside the engine compartment, torque them to 17 inch lbs. (1.9 Nm)
 
h.  Vacuum hoses
 
i.  Air inlet assembly, if equipped

2.  Install the instrument panel as follows:

  1. Rest the instrument panel on the lower pivot studs.
    2.  
  2. Attach the electrical connections.
    3.  
  3. Install but do not tighten the 4 upper instrument panel support screws.
    4.  
  4. Install the left and right panel pivot bolts. Tighten the bolts to 102 inch lbs. (11.5 Nm).
    5.  
  5. Install the panel lower support bolt. Tighten the bolt to 102 inch lbs. (11.5 Nm).
    6.  
  6. Tighten the upper support screws to 17 inch lbs. (1.9 Nm).
    7.  
  7. Install the windshield defroster grille and the speaker grilles.
    8.  
  8. Install the radio and storage compartment assembly (if equipped).
    9.  
  9. If removed, install the instrument cluster.
    10.  
  10. Install the heater and/or air conditioning control assembly.
    11.  
  11. Attach the electrical connections to the instrument panel accessory trim plate.
    12.  
  12. Place the trim plate in position and install its retaining screws. Tighten the screws to 17 inch lbs. (1.9 Nm).
    13.  
  13. Place the steering column into position and install its retaining nuts. Tighten the nuts to 22 ft. lbs. (30 Nm).
    14.  
  14. Attach the lighter electrical connection and the lap cooler duct to the knee bolster.
    15.  
  15. Place the knee bolster into position and install its retaining screws. Tighten the Torx® head screws to 80 inch lbs. (9 Nm) and the hex head screws to 17 inch lbs. (1.9 Nm).
    16.  
  16. Place the courtesy lamp in position and install its screws. Tighten the screws to 17 inch lbs. (1.9 Nm).
    17.  
  17. Place the instrument panel center sound insulator in position. Install the screws that attach the center sound insulator to the knee bolster, instrument panel and the floor duct. Tighten the screws to 17 inch lbs. (1.9 Nm).
    18.  
  18. Install the screw that attaches the center sound insulator to the heater assembly. Tighten the screw to 13 inch lbs. (1.5 Nm).
    19.  
  19. Install the remote control door lock receiver module to the instrument panel left side sound insulator.
    20.  
  20. Attach the door lock receiver electrical connection.
    21.  
  21. Install the nut that attaches the left side sound insulator to the accelerator pedal bracket. Tighten the nut to 35 inch lbs. (4 Nm).
    22.  
  22. Install the screw that attaches the left side sound insulator to cowl panel. Tighten the screw to 13 inch lbs. (1.5 Nm).
    23.  
  23. Install the screws that attach the left side sound insulator to knee bolster. Tighten the screw to 17 inch lbs. (1.9 Nm).
    24.  
  24. Feed the DLC through the hole in the sound insulator, place the DLC in position and install its retaining screws. Tighten the screws to 21 inch lbs. (2.4 Nm).
    25.  
  25. Install the right side sound insulator and tighten the screws
    26.  
  26. Connect the parking brake release cable to the lever.
    27.  
  27. Enable the air bag system.

3.  Install the heater hoses to the heater core.
 
4.  Refill the cooling system.
 
5.  Connect the negative battery cable.
 
6.  Run the engine to normal operating temperatures; then, check the climate control operation and check for leaks.

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