Many aspects of the heater system can malfunction which require. A air cabin filter is used to clean impurities from the air before it enters the ventilation system, when this filter becomes plugged it can slow the airflow in which case the needs replacement. An engine coolant leak can develop which hinders the performance of the heater system, these leaks must be before proper heater operation will return. When a heater core fails, a coolant residue may be observed upon the passenger side floorboard, this will typically be accompanied by a sweet, pungent odor. Most heater core inlet hoses can be identified by the diameter sizes of 1/2", 5/8" and 3/4".
Before you get started you should remove the plastic cowl cover from the engine bay to gain access to the two heater core hoses ports just to the side of the battery. I used a six-foot length of 3/4-inch heater hose, purchased at a local auto parts store. I sliced off a small length of hose to connect to my garden hose. The other end I ran down through the engine bay to a drain pan on the ground.
Because I already had the front bumper off of the car, I decided to drain a little bit of coolant out of the system in order to minimize the spillage of coolant cause by removing the heater core hoses. I'm not sure if it made much of a difference in this regard, so you can consider this step optional. I used a random hose to direct the coolant from the radiator petcock to the drain pan. For more information on this, see the Coolant Replacement article.
Reattach the heater core hoses, but leave the left (passenger side) hose off slightly so that the hole on top is exposed to allow air to escape as the system is filled up. You can test whether the hole is open by passing a small screwdriver through it.