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Volvo Bus Service and Maintenance Manual

 Cooling system
24 Check the radiator and fan shroud mounting. Look for dirt and dust on the radiator core and around the shroud. If it is necessary to top-up, check the cooling system and heater for visible coolant leaks.
25 Check the fan drive belts, their condition and if they are loose. Check the fan drive mounting, look for looseness in the support bearings, joints and splines (applies particularly to the propshaft driven fan).
26 Check the cooling fan condition and mounting (fixed fan). Check that the thermostat-controlled fan rotates easily.


Any dirt on the radiator fins will impede the air flowing through the radiator. This will impair the efficiency of the cooling system. The cooling capacity will be reduced. The radiator is cleaned by directing pressurized water or air from the rear side of the radiator.

NOTE! High pressure flushing may damage the radiator fins. With the prevalence of grease, use a degreaser.

Cleaning the engine

Cooling fan drive

Mechanical drive

Drive belts

Check/adjust belt tension. Replace worn belts in pairs.

Tensioning fan belt
1.Lock nuts for tensioning roller
2.Tensioning screw

Fan propshaft

The fan propshaft carrier bearings, joints and splines must not be loose. The sprider must no bind. Check the rubber coupling between the engine and fan propshaft. If worn, replace the rubber coupling according to Service Manual, Section 2.

Hydraulic drive BIOR

At an engine speed of 1000 r/min, the fan speed should be approx. 800 r/min; at an engine speed of 2000 r/min, the fan speed should be approx. 1800 r/min.

Hydraulic drive, other buses

At an engine speed of 1600 r/min, the fan speed should be approx. 2100±400 r/min.

Thermostat-regulated fan

If engine temperature is too high, check the fan operation with an optical tachometer. If the coolant temperature rises, thus indicating poor fan function, lock the fan temporarily and check. With the ambient air temperature at maximum 25°C, the fan speed should not rise when engine speed is increased to 1500 r/min.

Fan speed check with optical tachometer