COOLING SYSTEM
7.3.1
ENGINE VENTING
A single engine vent location is provided at the top of the EGR cooler. Vent lines from each
cylinder head are tied together with the EGR cooler vent. This is intended to be used to release
trapped air to the surge tank. This vent line should go to the top of the cooling system surge tank,
above the water line. The vent line must include a restriction of 4.5 mm diameter.
7.4
WATER PUMP
The centrifugal-type water pump circulates the engine coolant through the coolant system.
The pump is mounted on the front of the engine block and is belt driven by the crankshaft pulley.
7.5
TYPES OF COOLING SYSTEMS
Radiator cooling systems can be classi
fi
ed into two broad categories: rapid warm-up and
conventional. Only rapid warm-up systems are acceptable on the MBE4000.
7.5.1
RAPID WARM-UP COOLING SYSTEM
The rapid warm-up cooling system eliminates coolant
fl
ow through the radiator core during
closed thermostat operation.
This reduces warm-up time and maintains coolant temperature near the thermostat start to open
value. Having the deaeration tank (internal or remote) separated from the radiator core will
accomplish this. External vent and
fi
ll lines as well as internal standpipe(s) (radiator core air vent)
are required in the deaeration tank. Proper size and location of these components are critical to
having a balanced system. The
fi
ll line coolant return
fl
ow capabilities
must
exceed the
fl
ow into
the tank under all operating modes. Positive water pump inlet pressure must be maintained in
all operating conditions. The rapid warm-up cooling system has also been called positemp,
continuous deaeration, or improved deaeration.
Another advantage of this system is its ability to place a positive head on the water pump, thus
reducing the possibility of cavitation (see Figure 7-5 and Figure 7-6).
7-8
All information subject to change without notice.
(Rev. 03/06)
7SA250 0603
Copyright © 2006 DETROIT DIESEL CORPORATION