Honda Accord/Civic/Prelude 1973-1983 Repair Guide

Heater Core



Only the 1983 Prelude model may have the heater core replaced without removing the heater assembly. On all other models, remove the heater assembly (refer to the necessary service procedures) then disassemble the heater box and remove the heater core. Install the heater core in the the heater box (seal heater box with a gasket or sealant before installation) and then install the heater box assembly in the vehicle. Check the system for proper operation.

1983 Prelude
  1. Disconnect the negative battery cable. Drain the cooling system. Remove the heater pipe cover and heater pipe clamps.

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Remove the heater core retaining plate.
  3. Pull the cotter pin out of the hose clamp joint and separate the heater pipes.

Engine coolant will drain from the heater pipes when they are disconnected. Place a drip pan under the pipes to catch the coolant.

  1. When all the coolant has drained from the heater core, remove it from the heater housing.
  3. Installation is the reverse of the removal procedure, please note the following:
    1. Replace the hose clamps with new ones.
    3. Turn the cotter pin in the hose clamps tightly to prevent leaking coolant.
    5. Fill the cooling system with coolant and open the bleed bolt until coolant begins to flow from it. Tighten the bolt when all the air has escaped from the system.