[header] How to install a heater core in a chevy cavalier [title] Detach the negative battery line. [title] Lift the front end of your car and prop it up on jack stands. [title] Empty the radiator and loosen the seal to release the valve located under the front passenger's side. 
[title] Disconnect and remove the a/c heater drain tube from the firewall, if the car is equipped with air conditioning. [title] Detach the hoses from the heater core by releasing the clamps.