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Eric, Automotive Repair Shop Manager
Category: Chevy
Satisfied Customers: 31900
Experience:  20+ yrs. experience as repair shop manager and technician.
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How do I change heating core for 91 chevy S10

Resolved Question:

I need to know everything you take apart to get to heater core? And diagram, if posible.For 91 chevy S10 Engine 4.3L Tahoe.
Submitted: 9 years ago.
Category: Chevy
Expert:  Eric replied 9 years ago.


Here are directions:

  1. Disconnect the negative battery cable.

  2. Position a drain pan under the radiator, open the drain cock and drain the cooling system to a level below the heater core.

Plug the heater core tubes to avoid spilling coolant in the passenger compartment during removal.

  1. Disconnect the heater-to-engine coolant hoses from the core tubes on the fire wall, in the engine compartment.

Click image to see an enlarged view
Fig. 1: Exploded view of a heater core and case assembly


  1. From the passenger compartment (under the dash) remove the heater core rear case cover-to-cowl screws, then remove the cover from the vehicle.

Although not required, partial removal of instrument panel may make access to heater core case screws easier. Instrument panel directions at bottom of page.

  1. Remove the straps or brackets from each end of the heater core.

  2. Carefully remove the heater core from the cowl and case.

To install:

  1. Insert the heater core into the case, taking care not to damage the tubes as they are inserted through the cowl.

  2. Install the straps or brackets to the ends of the heater core and secure using the retaining screws.

  3. Install the heater core rear case cover and secure using the retaining screws.

  4. If moved for access, reposition and secure the dash mounted cabin light and housing.

  5. Connect the heater-to-engine coolant hoses to the core tubes.

  6. Connect the negative battery cable, then properly refill the engine cooling system.

  7. Run the engine at normal operating temperatures and check for leaks.

Click image to see an enlarged view
Fig. 2: If necessary loosen and remove the under dash cabin light retaining bolt


Click image to see an enlarged view
Fig. 3: With the bolt removed, the light and housing may be repositioned out of the way


Click image to see an enlarged view
Fig. 4: Loosen and remove the rear case cover screws


Click image to see an enlarged view
Fig. 5: Remove the rear case cover for access to the heater core


Click image to see an enlarged view
Fig. 6: Loosen and remove the core strap/bracket retainers


Click image to see an enlarged view
Fig. 7: Remove or reposition the straps/brackets so the core can be removed


Click image to see an enlarged view
Fig. 8: Most cores are retained by straps/brackets on both ends, don't forget to loosen all retainers


Click image to see an enlarged view
Fig. 9: Carefully withdraw the heater core from the case

Instrument Panel Directions:(only do if you cannot access all heater case screws easily)

  • Remove the ashtray.

  • Unfasten the accessory trim plate screws, then remove the accessory trim plate.

  • Remove the glove box door strap, then remove the glove box hinge screws.

  • Remove the glove box door frame.

  • Loosen the ashtray support screws, then remove the ashtray support.

  • Remove the glove box.

  • Unfasten the radio bracket bushing nut, then remove the radio.

  • Disconnect the speaker grille screws, then remove the speaker grilles.

  • Loosen the speaker retainers, then remove the front radio speakers.

  • Unfasten the sound insulation panel screws, then remove the sound insulation panels.

  • Loosen the steering column filler screws, then remove the steering column filler.

  • Disconnect the hood release cable.

  • Disconnect the shift indicator cable from the column bowl.

  • Disconnect the steering column support nuts, then lower the steering column. For details regarding this procedure, please refer to Suspension & Steering of this guide.

  • Unfasten the switch plate trim screw, then remove the switch trim plate.

  • Disengage the electrical wiring harness from the rear defogger and the light switches.

  • Disconnect the heater and A/C control.

  • Disconnect the cluster housing bezel mounting nuts, then remove the bezel.

  • Remove the instrument cluster from the vehicle. Disconnect and allow to hang:

  • The speedometer instrument panel electrical connector and the Vehicle Speed Sensor connector

  • The courtesy lamps and the cruise control module

  • The horn relay, multi-function alarm and the flasher assembly

  • If necessary, remove the applicable computer control module.

  • Remove the instrument panel-to-cowl mounts:

    1. Unfasten the screws from under the panel.

    2. Remove the instrument panel support.

    3. Unfasten the screws in the defroster outlets.

    4. Remove the ductwork, dash plugs, wire looms, and heater cables attached to the panel.

  • Disengage any electrical connections/wires routed through the instrument panel, then remove the instrument panel from the vehicle.

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    Customer: replied 9 years ago.
    Reply to eric's Post: Is there any way to get to top screws,with out taken apart the dash board? and how many screws are on the top.and is there a way to take glove box out.I have taken out radio and outside frame and door of glove box.