Shown on engine 471.9, engine version Euro VI Standard |
1 | Oil/coolant module |
1.1 | Coolant thermostat |
1.2 | Coolant pump |
2 | Cylinder liner |
3 | Cylinder head |
4 | Coolant manifold |
5 | Nozzle unit (for regenerating the diesel particulate filter (DPF)) (only with engine version Euro VI Standard) |
6 | Exhaust gas recirculation cooler |
8 | Fuel cooler |
9 | Compressor |
12 | Fan |
14 | Coolant feed to AdBlue® heater |
KA | Coolant outlet to cooler |
KE | Coolant inlet from cooler |
W20.00-1073-76
General
The engines have a closed engine cooling system (pressurized system). The coolant in the engine cooling system, which is circulated by the coolant pump (1.2), absorbs heat from the hot engine component parts. When the engine reaches its operating temperature, the heat is released to the outside air by a cooler.
Engine cooling circuit
The coolant pump (1.2) is belt driven. If the engine is running and has not yet reached its operating temperature, the coolant circulates within the engine. On vehicles with a regulated coolant pump (1.2), the rotational speed of the coolant pump (1.2) is monitored constantly. The engine management control unit (MC) (A4) reads the signals from the coolant pump rpm sensor (B640) and continuously regulates the delivery rate of the coolant pump (1.2). To do so, the engine management control unit (MCM) (A4) actuates the coolant pump solenoid valve (Y631).
Since the coolant thermostat (1.1) is closed when the engine is cold, the coolant flows through the coolant bypass into the oil/coolant module (1). There, it is routed past the closed coolant thermostat (1.1) through the coolant pump (1.2) to the heat exchanger (oil/water).
If the engine oil temperature is hotter than 115 °C (opening temperature for the oil thermostat), it is cooled by the heat exchanger (oil/water) so that it does not exceed a temperature of 120 °C. The heat exchanger (oil/water) is mounted on the oil/coolant module (1) and protrudes into the crankcase.
In this manner, the coolant flows into the crankcase, and thus into the cylinder liners (2). In the process, a part of the coolant is routed to the fuel cooler (8) and to the compressor (9), and through separate feed lines to the exhaust gas recirculation cooler (6) and to the exhaust gas recirculation positioner (Y621) at the same time.
The coolant returns directly to the coolant pump (1.2) from the fuel cooler (8) and the compressor (9).
The coolant that was pumped to the cylinder liners (2) then flows to the cylinder head (3).
The cylinder head (3) is fitted with a split coolant jacket. This means the coolant flows into the cylinder head (3) on both the intake and the outlet sides after it has flowed around the cylinders. In the cylinder head (3), the coolant flows first to the lower cooling level, where it bathes the fuel injectors and the valve seat rings.
Finally, the coolant flows to the upper cooling level and cools the valve guides located there.
Afterwards, the coolant is routed out into the coolant pipe manifold (4), into which the coolant from the exhaust gas recirculation cooler (6) and the coolant from the exhaust gas recirculation positioner (Y621) are also routed.
From the coolant pipe manifold (4), the coolant returns to the oil/coolant module (1) and to the coolant pump (1.2) through the coolant bypass and the coolant thermostat (1.1, still closed) until the engine reaches its operating temperature.
When the engine operating temperature is reached, the cooler circuit is activated through the opening of the coolant thermostat (1.1).
Depending on the position of the coolant thermostat (1.1), more or less coolant now flows through the vehicle cooler or directly to the coolant pump (1.2) through the coolant bypass. The temperature of the coolant in the coolant circuit is regulated in this way.
The fan (12) is used to increase the vehicle cooler's cooling output.
During this, the coolant temperature is constantly monitored by the coolant outlet temperature sensor (B606) and the coolant inlet temperature sensor (B607), which are both read by the engine management control unit (MCM) (A4).
The various pressures in the engine cooling system which arise due to the temperature fluctuations are balanced out over the coolant expansion reservoir.
Connection for the secondary coolant-retarder (only with a secondary coolant-retarder)
The coolant for the secondary coolant-retarder is taken from the coolant pipe manifold (4). Due to the fact that when the secondary water retarder is activated a large volume of coolant is taken from the coolant circuit, thereby causing the pressure in the engine cooling system to be greatly reduced, this pressure is regulated by the targeted injection of compressed air from the auxiliary consumer circuit.
To do so, the drive control (CPC) control unit (A3) uses the coolant pressure control sensor (B87) to permanently monitor the pressure in the coolant expansion reservoir. Under a certain pressure and dependent on the coolant temperature, it actuates the coolant pressure solenoid valve control (Y53), which accordingly allows compressed air to pass through the consumer circuit in the coolant expansion reservoir.
Cooling the nozzle unit (5) for regenerating the DPF (only with engine version Euro VI Standard)
Coolant for cooling the nozzle unit (5) is taken from the exhaust gas recirculation cooler (6). Next, it is routed back into the coolant pipe manifold (4) through the nozzle unit (5), in which the injection nozzle is located..
AdBlue® heater
The coolant for AdBlue® heating is also taken from the coolant pipe manifold (4). When the AdBlue® heating coolant solenoid valve (Y627) is actuated, the coolant is routed through the hose package to the AdBlue® container and from there back to the oil/coolant module (1).
Coolant circuit schematic | |||
Engine management (MCM) control unit, component description | A4 | ||
Coolant pressure control sensor, component description | Engine 470.9, 471.9 in model 800.110/112Secondary water retarder | ||
Coolant outlet temperature sensor component description | B606 | ||
Coolant inlet temperature sensor, component description | B607 | ||
Coolant pump component description | Engine 470.9, 471.9 in model 800.110/112Coolant pump, regulated | ||
Coolant pressure control solenoid valve, component description | Engine 470.9, 471.9 in model 800.110/112Secondary water retarder | ||
Component description for exhaust gas recirculation actuator | Y621 | ||
AdBlue(R) heating coolant solenoid valve, component description | Y627 | ||
Component description for exhaust gas recirculation cooler | |||
Oil/coolant module, component description | |||
Oil-water heat exchanger component description | |||
Component description for the coolant thermostat | |||
Nozzle unit for DPF regeneration, component description | Engine 470.9, 471.9 in model 800.110/112Engine version Euro-VI standard |