1986-1999 GM Bonneville/Eighty Eight/LeSabre Heater Core Removal/Installation
For 1987-91 Vehicles
1. Disconnect the negative battery cable. Drain the coolant into a clean container for reuse.
When draining the coolant, keep in mind that cats and dogs are attracted by 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.
2. Remove the right side sound insulator. Remove the underdash and splash cover covering the heater hoses in the engine
a. Remove the center and lower instrument panel trim plates.
3. Disconnect the heater hoses from the heater core. You may need tool J37097 or equivalent hose clamp removal pliers in
order to remove the hoses.
4. If equipped with electronic climate control, perform the following steps:
a. Disconnect the wires and the hose from the programmer.
b. Remove the programmer linkage cover and linkage.
c. Remove the programmer mounting bolts and the programmer.
5. Remove the heater core cover screws, then remove the cover.
6. Unfasten the heater core retainers, then remove the heater core assembly.