B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 008-042   Radiator

Air forced through the fins of the radiator by a fan cools the coolant pumped through the radiator. Environmental debris (paper, straw, lint, dust, etc.) can obstruct the fins and stop the flow of air which will reduce the cooling effect of the radiator.

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 air flow and 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 that the coolant temperature sensor is functioning correctly.

Shutters are designed to control air flow across the radiator. If the shutters fail to open when needed, the engine can run hot. Failure of the shutters to close can result in too much air flow and the engine running cold.

NOTE: Make sure that the air temperature sensor is functioning correctly. Check the air operated shutter controls. Check for air leaks.

Winterfronts can be used on a charge air cooled engine, but must be designed to partially cover the frontal area of the cooling system. A minimum of 120 square inches of charge air cooled frontal area must be left open to air flow.

An incorrect fan shroud or obstructions can reduce air flow and cause the engine to run hot.

NOTE: Check to be sure air is not recirculating. Check for missing baffles.