How to replace heater core on 1990 gmc 2500 - 1990 GMC Sierra

SOURCE: changing a heater core

here is a step by step diagram to replace your heater core
Front

1. Disconnect the negative battery cable.
   
2. Drain the cooling system.
   
3. Remove the instrument panel glove compartment.
   
4. Tag and unplug all electrical leads as necessary.
   
5. Remove the center air distribution duct from the floor.
   
6. If necessary, remove the ECM and mounting tray.
   
7. Remove the hinge pillar trim panels.
   
8. Remove the blower motor cover and then remove the motor.
   
9. Remove the steering wheel and tilt back the instrument panel slightly.
   
10. Remove the coolant overflow tank. Disengage the heater hoses at the core connections.
    
11. Unfasten the attaching screws and nut and then remove the heater case.
    
12. Remove the seven screws and lift off the heater case cover.
    
13. Remove the fasteners and brackets that hold the heater core to the case and lift the core from the case.
    

1. Install the heater core in the case.
   
2. Install the heater case bottom plate. Make sure there is a good seal.
   
3. Install the heater case into the truck. Tighten the 4 lower screws to 17 inch lbs. (2 Nm); the upper screw to 97 inch lbs. (11 Nm); and the nuts to 25 inch lbs. (2.8 Nm).
   
4. Connect the heater hoses at the core tubes.
   
5. Install the coolant overflow tank.
   
6. Install the instrument panel and the steering wheel.
   
7. Install the blower motor and cover.
   
8. Install the trim panels and if removed, the ECM. Install the air distribution duct and reconnect all electrical leads.
   
9. Install the glove compartment. Fill the cooling system and connect the battery cable.
   

1. Disconnect the negative battery cable.
   
2. Drain the engine cooling system into a clean container for reuse.
   
3. Disconnect the heater hoses from the heater core.
   
4. Remove the instrument panel storage compartment.
   
5. Disconnect the electrical connectors, as necessary, that may be in the way.
   
6. Remove the center floor air distribution duct.
   
7. Remove the hinge pillar trim kick panels.
   
8. Remove the blower motor cover screws and the cover.
   
9. Remove the blower motor screws and the blower motor.
   
10. Remove the steering wheel and the steering column (standard & tilt).
    
11. Remove the instrument panel fasteners and pull the instrument panel back far enough to gain access to the heater assembly.
    
12. While holding the heater assembly against the firewall, remove the screw located on the interior side near the evaporator pipe, if equipped.
    
13. In the engine compartment, remove the 4 heater assembly-to-chassis screws and the 2 heater assembly-to-chassis nuts.
    
    NOTE Removal of the heater assembly may require the help of an assistant.
    
14. Remove the 7 heater cover-to-heater assembly screws and the cover.
    
15. Remove the heater core from the heater assembly.
    View of the front heater assembly—Chevy/GMC C/K-Series, Blazer, Jimmy, Sierra, Suburban, Tahoe, Yukon
    Click to Enlarge Location of the front heater assembly-to-chassis fasteners—Chevy/GMC C/K-Series, Blazer, Jimmy, Sierra, Suburban, Tahoe, Yukon
    Click to Enlarge

1. Install the heater core to the heater assembly.
   
2. Install the heater cover and the 7 heater cover-to-heater assembly screws.
   
   NOTE Installation of the heater assembly may require the help of an assistant.
   
3. In the engine compartment, install the 4 heater assembly-to-chassis screws and the 2 heater assembly-to-chassis nuts. Torque the screws to 17 inch lbs. (1.9 Nm) and the nuts to 25 inch lbs. (2.8 Nm).
   
4. While holding the heater assembly against the firewall, install the screw located on the interior side near the evaporator pipe, if equipped. Torque the screw to 97 inch lbs. (11 Nm).
   
5. Install the instrument panel and the instrument panel fasteners.
   
6. Install the steering column (standard & tilt) and the steering wheel.
   
7. Install the blower motor and the blower motor screws.
   
8. Install the blower motor the cover and the cover screws.
   
9. Install the hinge pillar trim kick panels.
   
10. Install the center floor air distribution duct.
    
11. Connect the electrical connectors that were disconnected.
    
12. Install the instrument panel storage compartment.
    
13. Disconnect the heater hoses to the heater core.
    
14. Refill the engine cooling system.
    
15. Connect the negative battery cable.
    
16. Run the engine to normal operating temperatures; then, check the climate control operation and check for leaks.
    

Corey Malone

• 48 Answers
• Posted on May 27, 2009

SOURCE: heater core replacement

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You have to remove the entire front of the heater case to change thecore. This usually looks a lot easier in print than it actually IS.Theinstructions say to remove the lower part of the dash for access; usually youdon't have to remove the entire dash for this type of service, althoughsometimes it makes things easier if you loosen and remove any components notmentioned in the procedure that are in your way.
This kind of repair can be frustrating, as it involves working in tightplaces and with 1/4 drive extensions and universal sockets to get all thefasteners out, but it IS possible.Here is what I have for the factoryprocedure. I don't know of any shortcuts to make the process easier; if you can'tget it off, perhaps removing the dash completely for more room would be aviable option...


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Dana Newcombe

• 1564 Answers
• Posted on Oct 04, 2009

SOURCE: Replacing heater core in 2000 GMC sonoma. Dash is

If the dash is removed you've saved about 9 10ths of the job endurance. Look around, what you believe to be, the perimeter of the heater box. I cannot, and no one else can, tell you exactly where the bolts and nuts that mount the heater box are. Therefore you must viually sixe the box and check outide in the engine compartment and inside under the dash for the mounting bolts.You'll want to start by removing the heater hoses. Then starting at the passenger side engine compartment look for a group of 10mm or 7/16ths nuts retaining the housing and remove them. Do the same inside. The housing is usually held together with screws or clips, it changes year to year. Keep a log or pix of the wires and cables and hoses(vacuum) that are connected to the housing for reassembly. You'll need to "roll" the box out from under the dash depending on how much of the dash has been removed. The core is easy to spot for is has two hoses sticking out, and, is encircled with clips or screws . Also make sure you remove the bracket around the two entry hoses if it has one. Thank you, Dana

SOURCE: how tro replace heater core in 2003 dodge Ram PU

dodge want $800 to$1000 for doing this and I can see why.You have to raise or remove the whole dash recover you a/c freon ,disconect your a/c lines and heater hoses remove your heater box and put on a work bench remove the top and remove heater core,now next the last one I did the new heater core will not fit you have to modify the box so your new heater core will fit,put it all back together and fill with coolant and charge a/c, man I got tirered just typing this much less doing it, I hope this helps

SOURCE: how do i replace the heater core on a 2001 chevy

pull the dash off theres the heater core on passenger side theres a inlet and outlet hose pull both off remove mountin bolts install new one reassemble dash