Heater Core

Complete replacement of the heater core in a 1992 Dodge Viper, requiring extensive dashboard disassembly and coolant system draining.

Warnings

Tools required

Parts

• Heater core × 1 — Use OEM specification
• Heater hose clamps × 2 — Worm-drive style
• Coolant (ethylene glycol 50/50) × 1 — OAT or Mopar-compatible
• Dashboard fastener assortment × 1 — Replacement clips as needed
• Heater core tube seals/gaskets × 1 — Often included with core

Fluids

• coolant — 24 qt

Preparation

1. Park vehicle on level surface and allow engine to cool completely (minimum 2 hours).
2. Disconnect negative battery cable and secure away from terminal.
3. Place absorbent towels or plastic sheeting on floor beneath dashboard and inside footwells to protect carpet from coolant spills.
4. Remove driver and passenger floor mats and set aside.
5. Open hood and locate radiator drain petcock at lower driver side of radiator.

Procedure

1. 1

   Drain cooling system
   Place drain pan beneath radiator drain petcock. Open petcock and drain coolant into pan. Once draining slows, remove radiator cap to allow complete drainage. Dispose of old coolant properly or save for reuse if clean and within service life. Once drained, hand-tighten drain petcock.
   Torque spec

   Drain Petcock7 Nm (5 lb-ft)
2. 2

   Disconnect heater hoses at firewall
   Locate the two heater hoses entering the firewall on the passenger side of the engine bay. Using hose clamp pliers or pliers, loosen the hose clamps on both heater hoses. Slide clamps back away from firewall connections. Gently twist and pull hoses off heater core tubes. Expect residual coolant to drain; have a rag or small pan ready. Cap or plug the hoses and firewall tubes to prevent further coolant loss and contamination.
   ⚠Residual coolant will drain from hoses and tubes. Have towels ready.
3. 3

   Remove instrument cluster bezel and cluster
   From the driver's seat, locate screws securing the instrument cluster bezel (the trim ring surrounding the gauges). Remove these screws around the perimeter of the bezel. Carefully pull the bezel away from the dashboard and set aside. Next, remove the screws securing the instrument cluster itself to the dashboard. Carefully pull the cluster forward, disconnect the electrical connectors from the rear of the cluster, then remove the cluster from the vehicle.
   Torque spec

   Dashboard Screws3 Nm (2 lb-ft)
4. 4

   Remove center console and shifter boot assembly
   Remove the screws securing the center console to the transmission tunnel and floor. The console is a multi-piece assembly; start by removing the rear section if equipped, then work forward. Disconnect any electrical connectors for power outlets or accessories. Lift the shifter boot and trim ring assembly, which may require removing the shift knob first (verify removal method/thread direction against the factory service manual). Remove console sections and set aside.
   ℹ️Label electrical connectors as you disconnect them to aid reassembly.
5. 5

   Remove lower dashboard panels and knee bolsters
   Working from both driver and passenger sides, locate and remove the lower dashboard trim panels (knee bolsters) beneath the steering column and on the passenger side. These are typically secured with screws along the top edge and may have clips along the bottom. Remove all visible screws, then carefully pull panels away to release clips. Disconnect any electrical connectors for courtesy lights or diagnostic ports before fully removing panels.
   Torque spec

   Dashboard Screws3 Nm (2 lb-ft)
6. 6

   Disconnect steering column and support
   Remove the screws or bolts securing the steering column upper and lower trim covers. Separate the covers to access the column mounting hardware. Locate the steering column mounting fasteners where the column attaches to the dashboard support structure. Remove these fasteners and carefully lower the steering column, supporting it to prevent strain on the intermediate shaft. You may need to loosen (not remove) the pinch bolt at the intermediate shaft for clearance. Support the column with mechanic's wire or rest it on the driver's seat with padding.
   ⚠Support the steering column weight to prevent damage to the intermediate shaft or wiring harness.
7. 7

   Disconnect dashboard electrical connectors and controls
   Working systematically across the dashboard, disconnect all electrical connectors for switches, HVAC controls, radio, and any other dash-mounted components. Label each connector with tape and marker for reassembly reference. Disconnect the HVAC control cable(s) from the heater/AC unit by releasing the cable clips at the blend door and mode door actuators. Disconnect antenna lead if radio is dash-mounted.
   ℹ️Take photos of connector locations and cable routing before disconnection to aid reassembly.
8. 8

   Remove dashboard mounting fasteners
   Locate all dashboard mounting bolts and screws. These are typically found along the top of the dashboard near the windshield (accessible with hood open or from inside), at the sides near the A-pillars, at the center support structure, and at the lower mounting points near the transmission tunnel. The 1992 Viper dashboard uses approximately 12-14 mounting bolts in these locations. Remove all mounting fasteners completely and set aside, organizing by location.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
9. 9

   Remove dashboard assembly
   With an assistant, carefully lift and pull the dashboard assembly rearward and upward to clear the windshield cowl and side mounting points. The assembly is large and unwieldy; work slowly and check for any remaining fasteners or harness connections that may restrict movement. Once clear of all attachment points, lift the dashboard out through the passenger door opening. Set the dashboard on a padded surface with the back side facing up for access to the HVAC housing.
   ⚠Dashboard is heavy and fragile. Use at least two people for removal to prevent damage.
10. 10

    Remove HVAC housing cover and access heater core
    With the dashboard inverted or positioned for access, locate the HVAC housing on the passenger side. Remove the screws securing the heater core access cover or the housing split-line screws. The housing may be split horizontally or have a dedicated heater core cover plate. Remove the cover screws and carefully separate the cover to expose the heater core.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)
11. 11

    Remove heater core from housing
    The heater core is held in the HVAC housing by mounting brackets or retaining straps. Remove the fasteners securing the heater core mounting brackets. Carefully slide the heater core out of the housing, noting the orientation and the position of any foam seals or air dams surrounding it. Residual coolant will drain from the core; have towels ready. Inspect the housing for debris, leaves, or corrosion and clean as necessary.
    ⚠Heater core tubes are fragile. Do not bend or force the core during removal.
    Torque spec

    Heater Core Mounting8 Nm (6 lb-ft)
12. 12

    Install new heater core
    Transfer any foam seals or insulation from the old heater core to the new unit if they are not pre-installed. Ensure the heater core tube seals/gaskets are in place on the new core tubes. Carefully slide the new heater core into the HVAC housing in the same orientation as the original. Align the mounting bracket holes and install the heater core mounting brackets and fasteners. Torque to specification.
    Torque spec

    Heater Core Mounting8 Nm (6 lb-ft)
13. 13

    Reassemble HVAC housing
    Reinstall the HVAC housing cover or close the housing split-line. Ensure all sealing surfaces are clean and that any gaskets or seals are properly seated. Install all housing cover screws and torque to specification. Verify that blend doors and mode doors inside the housing move freely and are not obstructed by the new heater core installation.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)
14. 14

    Reinstall dashboard assembly
    With an assistant, carefully position the dashboard assembly back into the vehicle. Guide the dashboard over the steering column support and align it with the mounting points at the windshield cowl, A-pillars, center support, and lower mounts. Start all dashboard mounting bolts by hand to ensure proper alignment before tightening. Once all bolts are started, torque the mounting bolts to specification working from the center outward.
    ⚠Verify that no wiring harnesses are pinched between the dashboard and body structure before tightening bolts.
    Torque spec

    Mounting Bolts27 Nm (20 lb-ft)
15. 15

    Reconnect all dashboard components and controls
    Reposition and secure the steering column to its mounting points. Reconnect all electrical connectors to switches, HVAC controls, radio, and instrument cluster, referring to labels and photos from disassembly. Reconnect HVAC control cables to the blend door and mode door actuators, ensuring proper cable routing and clip engagement. Reinstall the instrument cluster, connecting the electrical connectors, then secure with screws. Install the instrument cluster bezel. Reinstall all lower dashboard panels and knee bolsters. Reinstall the center console sections and shifter boot assembly. Verify that all controls, switches, and accessories function properly before proceeding.
    Torque spec

    Dashboard Screws3 Nm (2 lb-ft)
16. 16

    Reconnect heater hoses at firewall
    Remove any caps or plugs from the heater core tubes at the firewall and the heater hoses. Slide the heater hoses onto the heater core tubes at the firewall, ensuring they are fully seated. Position the hose clamps over the hose-to-tube connections and tighten to specification using a screwdriver or nut driver. Ensure clamps are positioned correctly to prevent leaks.
    Torque spec

    Heater Hose Clamps3 Nm (2 lb-ft)
17. 17

    Refill cooling system and bleed air
    Close the radiator drain petcock securely (hand tight per specification). Fill the cooling system with the correct conventional ethylene glycol 50/50 coolant through the manufacturer-specified fill point, per the factory-specified capacity. Fill slowly to allow air to escape. Once the radiator is full, install the radiator cap. Start the engine and allow it to reach operating temperature with the heater controls set to maximum heat and fan on high. Monitor coolant level and add as necessary as air is purged from the system. Check for leaks at the heater hose connections at the firewall. Once the engine reaches operating temperature and the thermostat opens, verify that hot coolant is circulating and that the heater produces hot air inside the vehicle. Shut off the engine, allow it to cool, and recheck the coolant level. Top off as needed.
    ⚠️Do not remove radiator cap while engine is hot. Allow engine to cool before checking coolant level after initial fill and bleed.
18. 18

    Final inspection and testing
    Reconnect the negative battery cable. Start the vehicle and verify that all dashboard gauges, warning lights, and controls function properly. Test the heater controls through all modes (defrost, floor, vent) and temperature settings (test A/C only if the vehicle is so equipped). Verify that airflow is as expected and that heating performance is normal. Check under the dashboard for any coolant leaks at the heater core connections inside the HVAC housing. Perform a final check for any loose panels, missing screws, or disconnected components. Reinstall floor mats.

Reassembly

1. Reassembly follows the reverse order of disassembly with attention to torque specifications.
2. Ensure all electrical connectors are fully seated and locked before securing dashboard panels.
3. Verify HVAC control cable operation and adjustment before finalizing dashboard installation.
4. Torque all fasteners to specification using a calibrated torque wrench.
5. Bleed the cooling system thoroughly to prevent air pockets that can cause heater performance issues or engine overheating.

Verification

• Start engine and verify no coolant leaks at heater hose connections at the firewall or inside the vehicle.
• Confirm heater produces hot air at all temperature settings and fan speeds.
• Check that coolant level is correct and system pressure is normal (no bubbles in overflow tank).
• Verify all dashboard controls, gauges, and accessories function properly.
• Test-drive vehicle to ensure heater performance is normal and coolant temperature remains stable.
• Recheck coolant level after test drive and top off if necessary.

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