How to change the back heater box of Buick gl8?

Do you mean how to disassemble the water tank of Buick gl8 heater? Just unscrew the drain bolt at the lower part of the water tank to collect the coolant.

1. Remove the wire harness clip in the upper cross member of the water tank and remove the wire harness.

2. Remove the air cleaner assembly and the control computer.

3. Remove the headlight on the right side, remove the fan bracket assembly, unscrew the drain bolt at the lower part of the water tank, and collect the coolant.