Heating Circuit; (B3H) Secondary Water Retarder - Mercedes-Benz OM 471 Introduction Into Service Manual

Functions
The coolant then flows from the fuel cooler (8) and the
compressor (9) straight back to the coolant pump (1.2).
The coolant pumped to the cylinder liners (2) then flows back to
the cylinder head (3).
The cylinder head (3) contains a partitioned coolant jacket. This
means that once the coolant has flushed the cylinders, both on
the inlet and the outlet sides, it then flows to the cylinder head
(3). In the cylinder head (3) the coolant flows first to the lower
cooling level where it flushes the fuel injectors and the valve seat
rings.
Finally, the coolant flows to the upper cooling level and cools the
valve guides located there.
After this the coolant is routed outwards into the coolant
manifold (4), into which the coolant from the exhaust gas
recirculation cooler (6) and the coolant from the exhaust gas
recirculation positioner (Y621) is routed.
The coolant flows from the coolant manifold (4) back over the
coolant bypass duct and the still closed coolant thermostat (1.1)
into the oil/coolant module (1) and to the coolant pump (1.2),
until the engine's operating temperature is reached.
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Heating circuit

The coolant for the heater circuit is taken from the coolant
manifold (4).
A shutoff valve is installed in front of the heater heat exchanger,
through which the coolant flow through the heater circuit or the
heater heat exchanger can be regulated.
In vehicles with code (D6I) Residual heat utilization, the additional
residual heat pump (M20) upstream of the heater shutoff valve
(Y49) ensures that the coolant is circulated in the heater circuit
when the engine is switched off. This in turn means that the
engine's residual heat can be used for up to two hours.
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Connection of secondary water retarder > in vehicles with code

(B3H) Secondary water retarder

The coolant for the secondary water retarder is also taken from
the coolant 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
cooling system to be greatly reduced, this is regulated by targeted
injection of compressed air from the 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
depending 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.
Coolant circuit schematic
Engine management control unit (MCM),
component description
Auxiliary heating heater, component
description
84
– This printout will not be recorded by the update service. Status: 09 / 2011 –
When the engine operating temperature is reached, the cooler
circuit is activated when the coolant thermostat (1.1) is opened.
Depending on the position of the coolant thermostat (1.1), more
or less coolant flows through the vehicle cooler or directly over
the coolant bypass line to the coolant pump (1.2). 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.
The coolant temperature is continuously monitored by the
coolant outlet temperature sensor (B606) and coolant inlet
temperature sensor (B607), both of which are connected to the
engine management (MCM) control unit (A4).
The various pressures in the cooling system, which are created by
the temperature fluctuations, are compensated for through the
coolant expansion reservoir, which > depending on the vehicle
equipment > is located either at the front behind the maintenance
flap or at the rear on the cab mounting crossmember.
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The auxiliary heater installed in vehicles with code (D6M) Cab
auxiliary water heater or with code (D6N) Cab and engine
auxiliary water heater, is integrated with an additional bypass line
into the heater circuit in such a way that the coolant is circulated
through the auxiliary circulation pump in the heater circuit only
and therefore does not have to be routed through the entire
engine.
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Cooling of injection nozzle for regeneration of diesel particulate
filter (DPF) > for vehicles with code (M5Z) Euro VI engine version
The coolant used for cooling the injection nozzle is taken from the
exhaust gas recirculation cooler (6), routed through the nozzle
unit for diesel particulate filter regeneration, in which the
injection nozzle is located, and routed back to the coolant
manifold (4).
AdBlue" heater
The coolant for the AdBlue" heater is also taken from the coolant
manifold (4). When the AdBlue" heater 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).
A4
A901
i Only in vehicles with code (D6M) Cab
auxiliary water heater or code (D6N) Cab
and engine auxiliary water heater.
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