The 1999 Chevrolet Z 71 heater core can be accessed by removing the passenger side kick panel. Remove the heater core water hoses. Remove the heater core retaining bolts. Reverse the process to install the new heater core.
The heater core on a 1999 Ford F250 Superduty is replaced by removing the heater hoses, disconnecting the wiring harness, and removing the retaining bolts. The cover can then be removed, the heater core unbolted, and removed from its housing.
To change the heater core on a 1999 Chevy 4-wheel drive, first remove the dashboard and drain the coolant. Unbolt the core from its mounts and remove the dash panel to be able to change the heater core.