How do I replace a heater core in 1986 cutlass supreme with the 231 or 3.8 litre motor??

Heater Core
GM Cutlass RWD 1970-1987 Repair Guide

1980-87 CARS

See Figures 1, 2, 3, 4, 5, 6, 7, 8 and 9
1.
Disconnect the negative battery cable

2.
Engage the right wiper arm so it is held in the UP position.

3.
Drain the radiator, disengage the heater core hoses, then disconnect the hoses and plug them.

4.
Pull off the trim seal and remove the screens from the assembly. Mark and remove any electrical connections in the way.

5.
Loosen and move up the lower windshield trim. Remove the windshield molding cowl brackets.

6.
Tape a strip of wood below the lower edge of the windshield glass near the module for protection. Remove all module cover screws.

7.
Cut through the sealing material along the cowl with a knife.

8.
Pry the module cover off from the side, not down from the top, to insure you don't damage the windshield.

9.
Lift the cover off and away from the flange of the fender-cowl brace.

10.
Remove the core.


To install:
1.
Apply a strip of caulk-type sealer when installing the module top.

2.
Install the core and module top cover

3.
Engage the electrical connections

4.
Connect the negative battery cable, refill the radiator and check for leaks


Click image to see an enlarged view
Fig. 1: Remove the heater core hoses; be sure the cooling system is drained first Heater Core GM Cutlass RWD 1970-1987 Repair Guide 1980-87 CARS See Figures 1, 2, 3, 4, 5, 6, 7, 8 and 9 1. Disconnect the negative battery cable 2. Engage the right wiper arm so it is held in the UP position. 3. Drain the radiator, disengage the heater core hoses, then disconnect the hoses and plug them. 4. Pull off the trim seal and remove the screens from the assembly. Mark and remove any electrical connections in the way. 5. Loosen and move up the lower windshield trim. Remove the windshield molding cowl brackets. 6. Tape a strip of wood below the lower edge of the windshield glass near the module for protection. Remove all module cover screws. 7. Cut through the sealing material along the cowl with a knife. 8. Pry the module cover off from the side, not down from the top, to insure you don't damage the windshield. 9. Lift the cover off and away from the flange of the fender-cowl brace. 10. Remove the core. To install: 1. Apply a strip of caulk-type sealer when installing the module top. 2. Install the core and module top cover 3. Engage the electrical connections 4. Connect the negative battery cable, refill the radiator and check for leaks Click image to see an enlarged view Fig. 1: Remove the heater core hoses; be sure the cooling system is drained first