and, through the use of an internal baffle, distributes it
across the top of the core.
b. The core is made up of numerous rows of small
vertical tubes that connect the upper and lower radiator
tanks. Sandwiched between the rows of tubes are thin
sheet metal fins. As the coolant passes through the
tubes to the lower tank the fins conduct the heat away
from it and dissipate this heat into the atmosphere. The
dissipation of the heat from the fins is aided by directing
a constant airflow between the tubes and over the fins.
c. The lower tank collects the coolant from the core
and discharges it to the engine through the outlet pipe
d. The overflow pipe provides an opening from the
radiator for escape of coolant or steam if pressure in the
system exceeds the regulated maximum. This will
prevent rupture of cooling system components. Some
radiators are designed with their tanks on the sides in a
vertical position. They are connected by a core that
Figure 9-3. Water Pump Construction
contains horizontal tubes. This radiator configuration is
called a crossflow radiator and operates in the same
loaded seal to prevent coolant leakage.
manner as the conventional vertical flow radiator, though
it should be noted that there is no thermosiphon effect
9-8. Fan and Shrouding (Fig. 9-1). The fan pulls a
(para 9-3) with a cross flow radiator.
large volume of air through the radiator core so that
engine heat can be dissipated effectively. In most cases
9-7. Water Pump (Fig. 9-3). All modern cooling
the fan works in an enclosure called a shroud to ensure
systems have water pumps to circulate the coolant. The
maximum efficiency of the fan. There are two methods
pump, usually located on the front side of the engine
of driving a fan. One method is to attach it to the end of
block, receives coolant from the lower tank and force sit
the water pump shaft. The other method that is
through the water jacket into the upper radiator tank.
becoming increasingly popular is to utilize an electric
The pump is a centrifugal type and has an impeller with
blades that force coolant outward as the impeller rotates.
It usually is driven by the engine crankshaft through a V-
a. Thermostatically Controlled Engine-Driven Fan.
belt. Advantages of a centrifugal pump as a water pump
Some vehicles are equipped with a seven-blade fan,
are that it is inexpensive, circulates great quantities of
particularly those for heavy-duty use or those with air
coolant for its size, and is not clogged by small amounts
This fan configuration will move
of foreign matter. Another advantage is that a centrifugal
tremendous amounts of air through the radiator to
pump permits a limited amount of thermosiphon action
provide extra cooling capacity. The problem with a high-
after the engine is shut down to help prevent boil over.
capacity fan is that it can cause the radiator core to
The pump housing usually is cast from iron or aluminum.
freeze in cold weather.
Other problems that are
The impeller can be made from iron, aluminum, or
associated with a high output fan are excessive power
plastic. It rides on a shaft that is supported in the
consumption and noise at highway speeds. Most seven-
housing on a sealed double row ball bearing. The pump
blade fans are driven by the water pump through a
viscous (fluid) clutch (fig. 9-4) to correct these conditions.
The fan clutch is designed to limit the fan speed based