Here are the steps on how to replace the heater core in a 1999 Z71 Chevy:
1. Disconnect the battery.
2. Remove the intake manifold.
3. Remove the heater box.
4. Remove the heater core.
5. Install the new heater core.
6. Reinstall the heater box.
7. Reinstall the intake manifold.
8. Reconnect the battery.
Here are some tips for replacing the heater core in a 1999 Z71 Chevy:
* Be careful not to damage the dashboard when removing it.
* Make sure to drain the coolant from the system before removing the heater core.
* Use new O-rings when installing the new heater core.
* Test the heater core before reinstalling the dashboard.
