Component Tests and General Diagnostics

PRELIMINARY CHECKS

ENGINE COOLING SYSTEM OVERHEATING

Establish what driving conditions caused the complaint. Abnormal loads on the cooling system such as the following may be the cause:

- Prolonged idle
- Very high ambient temperature
- Overloaded Truck
- Slow traffic
- Traffic jams
- High speed or steep grades
- Snow Plow restricting airflow through cooling module
- Debris on front of the grill or the cooling module that is restricting airflow
Driving techniques that avoid overheating are:
- Idle with A/C off when temperature gauge is at end of normal range.
- Increasing engine speed up to 2000 rpm with transmission in park or neutral for more airflow is recommended.
- If equipped with a snow plow. Activate the snow plow mode.

TRAILER TOWING:

Consult Trailer Towing section of the owners manual. Do not exceed the limits.

RECENT SERVICE OR ACCIDENT REPAIR:

Determine if any recent service has been performed on vehicle that may affect the cooling system. This may be:

- Engine adjustments (incorrect timing)
- Slipping engine accessory drive belt(s)
- Brakes (possibly dragging)
- Changed parts. Incorrect water pump or pump rotating in wrong direction due to belt not correctly routed
- Reconditioned radiator or cooling system refilling (possibly under filled or air trapped in system).
- Service to electrically controlled viscous fan clutch

NOTE: If investigation reveals none of the previous items as a cause for an engine overheating complaint, refer to the COOLING SYSTEM DIAGNOSIS CHART.

These charts are to be used as a quick-reference only.

COOLING SYSTEM DIAGNOSIS CHART