B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 008-040   Fan, Cooling

If the fan is belt-driven, a slipping belt will result in a slower fan speed and reduced cooling. A malfunctioning automatic belt tensioner can be the problem.

NOTE: Check the bearings in the fan hub and other pulleys to make sure they are not causing excessive belt vibration and slippage.

Interruption of the circuit to an electrically driven fan can result in insufficient airflow and can cause the engine to run hot.

NOTE: Make sure that the temperature sensor is functioning correctly.

Some applications use thermatic fans. These fans operate
only as needed to keep the coolant at the correct temperature. If the fan does not operate when the coolant temperature increases, the engine will run hot. If the fan does not shut off when coolant temperature decreases, the engine will run cold.

NOTE: Make sure the temperature sensor is functioning correctly.

3/8-Inch Square Drive

Lift the tensioner to relieve tension in the belt.

Remove the belt. Refer to Procedure 008-002.

NOTE: The belt tensioner is spring-loaded and must be pivoted away from the drive belt. Pivoting in the wrong direction can result in damage to the belt tensioner.

WARNING  Do not straighten a bent fan blade or continue to use a damaged fan. A bent or damaged fan blade can fail during operation and cause personal injury or property damage.

Inspection of the cooling fan is required daily. Check for cracks, loose rivets, and bent or loose blades. Check the fan to make sure it is securely mounted. Tighten the capscrews, if necessary.

Replace original equipment fan that is damaged with a fan of the identical part number. Cummins Engine Company must
approve any other fan changes to be covered under warranty.

8 mm, 10 mm

Install the spacer, fan, and fan capscrews.

8 mm

10 mm

3/8-Inch Square Drive

Lift and hold the belt tensioner.

Install the drive belt, and release the tensioner. Refer to Procedure 008-002.