Replace the worn wheel bearings.
2003 Ford Explorer Sport Trac Problem Reports
RepairPal Verified 2003 Ford Explorer Sport Trac Problem Reports
A failed heater blend door or actuator can cause the temperature control for the HVAC system to stop working. A clicking sound from the dash area would commonly indicate an actuator fault. If the heater gets stuck on the hottest setting, the heater blend door may be broken requiring replacement of the heater box to repair the issue.
Various problems with the 5-speed automatic transmission were common. These problems can be more common on the 2002 models with build dates before March, 2002. There are many service bulletins describing the diagnoses and repairs, which include fluid leak repairs, transmission software updates, or internal failures requiring a costly repair.
The composite (plastic) intake manifold may crack near the thermostat housing and cause a coolant leak. Ford released an updated manifold that was reinforced to prevent a recurrence. No recall was issued for this problem but Ford did extend the warranty to seven years on some models from the date of purchase.