Engine Cooling System – General Overview
Diesel cooling is liquid with forced circulation of coolant from a centrifugal pump. The design of the cooling system is shown in Figure 1.
1 — filler plug; 2 — expansion tank; 3 — upper radiator cap; 4 — radiator; 5 — pipe mounting bracket; 6 — radiator supply pipe;
7, 16 — pipe; 8 — fan casing; 9 — fan shaft pulley; 10 — fan drive housing; 11 — fan casing mounting frame; 12 — fan shaft drive belt;
13 — fan; 14 — tension roller; 15 — intermediate support bracket; 17 — outlet pipe; 18 — intermediate shaft drive belt;
19 — thermostat housing; 20 — water pump pulley; 21 — drive belt for the water pump and generator; 22 — crankshaft pulley
Temperature range: The temperature of the coolant in the cooling system must be maintained within 85–95°C. It is allowed to increase the coolant temperature to 105°C during short-term (no more than 20 minutes) operation at maximum torque.
The temperature of the coolant in the system is controlled by a remote thermometer, the sensor of which is installed in the cylinder head.
Attention! It is prohibited to operate the diesel engine when the coolant overheating lamp comes on.
Thermostat: The thermostat with solid filler is designed to accelerate engine warm-up after starting and automatically regulate temperature conditions at different loads and ambient temperatures. The temperature at which the thermostat begins to open is 85–89°C.
Expansion tank: The expansion tank is designed to compensate for changes in the volume of coolant when it is heated and to remove air.
Unit drive: The water pump and generator are driven from the engine crankshaft pulley through two V-belts. The engine cooling system fan is driven from the crankshaft pulley through the intermediate support pulley.
Cooling System Maintenance
Daily maintenance:
- Check the fluid level in the expansion tank (the level should be near the middle of the tank).
- Monitor the tightness of connections.
Attention! Operation of the bus with an empty expansion tank is not permitted.
Coolant replacement: Once a year in the fall, during seasonal maintenance, the coolant should be replaced. Before replacing the fluid, make sure the system is tight.
The density of the low-freezing liquid should be monitored before the start of the cold season, as well as after each repair of the cooling system associated with a coolant leak. External signs (color, smell, etc.) do not allow you to correctly determine the quality of the coolant.
Attention! The use of coolant of insufficient density can cause destruction of the diesel engine.
Starting and operating a diesel engine with an empty cooling system is prohibited.
A low-freezing liquid should be used as a coolant in the system.
Belt Tension Adjustment
Fan belt tension between the crankshaft pulley and the intermediate support is performed by turning the eccentric axis of the intermediate support after loosening the mounting nuts.
Belt tension between the fan pulleys and the intermediate support is carried out by a tension roller.
Tension control is carried out using a spring dynamometer based on the amount of belt deflection.
Permissible belt deflection under load 40 ± 2 N:
- In the area between the crankshaft and intermediate support pulleys — 14–20 mm;
- In the area between the intermediate support and fan shaft pulleys — 13–18 mm.
Lubrication of Cooling System Components
The bearings of the water pump, fan shaft, and intermediate fan support do not require lubrication during the entire period of operation.
"Litol-24" lubricant is placed in the bearing cavity of the water pump during assembly and is replaced only after repair (disassembly) of the unit.
Recommendation for winter operation: To maintain optimal engine thermal conditions at low temperatures, all radiator hatch grilles should be covered with insulation, and if necessary, remove the fan drive belt.
