The engine cooling system is of the closed type, with forced circulation of the coolant by a centrifugal pump.
The coolant temperature in the system is monitored by a remote thermometer, the sensor of which is installed in the cylinder head.
In addition, a sensor of the warning lamp for critical coolant temperature is installed in the cover of the thermostat housing.
Attention! Operation of the diesel engine is prohibited when the warning lamp for critical coolant temperature illuminates in the cooling system.
The coolant temperature in the cooling system must be maintained between 85 and 95 °C.
To accelerate the warming up of the diesel engine after starting and for automatic regulation of the temperature regime under various loads and ambient temperatures, a thermostat is used with an initial opening temperature of the main valve of 87 ± 2 °C.
The thermostat with solid filler is intended to accelerate the warming up of the engine after starting and for automatic regulation of the temperature regime under various loads and ambient temperatures.
The expansion tank is intended to compensate for the change in the volume of the coolant during heating and to remove air.
The liquid pump and the alternator are driven from the engine crankshaft pulley by means of two belts.
The engine cooling system fan is driven from the crankshaft pulley through the intermediate support pulley.
Attention! In order to avoid scale formation and damage to the engine, the use of water in the cooling system is not permitted.
If faults occur related to a coolant leak, temporary use of water is permitted until the faults are rectified.
Maintenance of the cooling system
During maintenance of the cooling system, the fluid level in the expansion tank is checked daily and the tightness of the connections is monitored.
Operation of the bus with an empty expansion tank is not permitted. The fluid level must be above the "MIN" mark on the tank body.
An antifreeze fluid should be used as the coolant in the system.
In order to avoid scale formation, the use of water in the cooling system is not permitted.
If a coolant leak appears, temporary use of water is permitted until the fault is rectified.
The density of the antifreeze fluid should be checked before the start of the cold period of the year, as well as after each repair of the cooling system related to a coolant leak.
External signs (colour, smell, etc.) do not allow the quality of the coolant to be correctly determined.
Once a year, in autumn, during maintenance, the coolant should be replaced.
Before replacing the fluid, it is necessary to make sure that the system is leak-tight.
Attention! The use of coolant of insufficient density may cause destruction of the engine.
Monitor the coolant temperature. The normal operating temperature should be 85–95 °C.
If the temperature rises above the operating temperature, check the coolant level in the expansion tank, if necessary in the radiator, check the tightness of the radiator and pipelines, check the tension of the fan belts and their condition.
If necessary, but not less frequently than every 120,000 km of bus mileage, flush the cooling system to remove contaminants.
For flushing, use a solution of 50–60 g of calcined soda per 1 litre of water.
Flush the system in the following order:
- pour 2 litres of kerosene into the radiator and fill the system with the prepared solution;
- start the diesel engine and let it run for 8–10 hours or cover 350–400 km, then drain the solution and flush the cooling system with clean water.
The tension of the fan belt between the crankshaft pulley and the intermediate support is adjusted by turning the eccentric axis of the intermediate support after slackening the nuts of its mounting.
The tension of the belt between the fan and intermediate support pulleys is adjusted by the tensioner roller.
The tension of the alternator and water pump drive belts is adjusted by turning the alternator housing.
The tension of the compressor drive belt on the D-245.9E3 diesel engine is adjusted by the roller through the tensioning mechanism.
Before tensioning, slacken the locking bolt of the tensioner roller axis and the locking nut of the adjusting screw.
Then, by turning the nut on the adjusting screw, move the screw together with the tensioner roller.
Tension is checked with a spring dynamometer by the amount of belt deflection or using the KI-8920 device.
The belt deflection under a load of 4 ± 0.2 kgf must be:
- in the section between the crankshaft and intermediate support pulleys — 14–20 mm;
- in the section between the intermediate support and fan shaft pulleys — 13–18 mm;
- in the section between the crankshaft and alternator pulleys — 15–22 mm;
- in the section between the alternator and water pump pulleys — 7–12 mm;
- in the section between the crankshaft and compressor pulleys — 15–22 mm.
If one of the belts is worn or damaged, replace them as a set (both belts).
The "Litol-24" grease is applied to the bearing cavity of the water pump during assembly and is replaced only after repair (dismantling) of the unit.
The bearings of the water pump, fan shaft and fan intermediate support do not require lubrication throughout the entire period of operation.
