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Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience:  40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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how can I replace 1999 cadillac Deville heater core

Customer Question

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Submitted: 10 years ago.
Category: Car
Expert:  Bob replied 10 years ago.

Heater Core Replacement

Removal Procedure

    Caution: Before servicing any electrical component, the ignition and start switch must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. If a tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable.
  2. Partially drain the coolant.
  3. Remove the instrument panel compartment.
  4. Remove the right sound insulator.
  5. Remove the heater and A/C programmer.
  6. Disconnect the driver air mix actuator (2).
  7. Disconnect the passenger air mix actuator (3).
    Object Number: 305037  Size: SH

  8. Remove the heater core cover.
    Object Number: 378606  Size: SH

  9. Remove the inlet and outlet heater hoses from the heater core.
    Object Number: 381380  Size: SH
  10. Remove the heater retaining screws.
  11. Remove the heater core.