Insufficient Air Flow

INSUFFICIENT AIR FLOW, CAUSES
Fan Clutch Slipping - The fan clutch fails to engage, resulting in the fan clutch slipping on the water pump shaft.

Missing Radiator Shroud - The shroud direct air flow from the fan through the radiator. With the shroud missing air is drawn around the radiator rather than through it.

Missing Fan Blades - Results in reduce air flow and an unbalanced fan.

SYMPTOMS
- Engine warms up normally but gradually overheats.
- Cooling system overheats when idling or driving at low speeds, but may operate normally at cruising or highway speeds.

NOTE: With speeds in excess of 25 mph, sufficient air flow is forced across the radiator to cool the engine without the use of the cooling fan (under normal conditions).

- Cooling system overheats when under heavy engine loads.
- Very little air flow is felt flowing over the engine during hot idle.

VERIFYING PROBLEM
Fan Clutch Slipping
- With the engine "OFF", and cold, the fan should spin loosely on the fan clutch.
- With the engine "OFF", and hot, there should be a noticeable resistance when attempting to spin the fan.
- Check the back of the fan clutch for oil/silicone leakage, if any oil leakage is detected the fan clutch should be replaced.

Fan Shrouds - Verify that all fan shrouds are in place.

Fan Blades - Verify that all blades are intact and undamaged.

CAUTION: Operating a cooling fan with damaged or missing blades is extremely dangerous. The vibration created by a missing/damaged blade may loosen other blades, causing them to fly off of the fan.