Upon leaving the thermostat housing, the coolant is by-
Keel Cooling System
passed directly to the bottom of the expansion tank until
the engine operating temperature, controlled by the
The keel cooling system is similar to the heat exchanger
thermostat, is reached. As the engine temperature
system, except that the coolant temperature is reduced
increases, the coolant is directed to the keel cooler,
in the keel cooler. In this system, the coolant is drawn
where the temperature of the coolant is reduced before
by the circulating pump from the bottom of the
flowing back to the expansion tank.
expansion tank through the engine oil cooler. From the
cooler the flow is the same as in the other systems.
ENGINE COOLING SYSTEM MAINTENANCE
coolant level should be within 2"of the top of the filler
The function of the engine coolant is to absorb the heat,
Should a daily loss of coolant be observed, and there
developed as a result of the combustion process in the
are no apparent leaks, there is a possibility of gases
cylinders, from the component parts such as exhaust
leaking past the cylinder head water seal rings into the
valves, cylinder liners and pistons which are surrounded
cooling system. The presence of air or gases in the
by water jackets. In addition, the heat absorbed by the
cooling system may be detected by connecting a rubber
oil is also removed by the engine coolant in the oil-to-
tube from the overflow pipe to a water container.
water oil cooler.
Bubbles in the water in the container during engine
operation will indicate this leakage. Another method for
For the recommended coolant, refer to Engine Coolant.
observing air in the cooling system is by inserting a
transparent tube in the water outlet line.
Cooling System Capacity
Drain Cooling System
The capacity of the basic engine cooling system
(cylinder block, head, thermostat housing and oil cooler
The engine coolant is drained by opening the cylinder
housing) is shown in Table 1.
block and radiator (heat exchanger) drain cocks and
removing the cooling system filler cap. Removal of the
To obtain the complete amount of coolant in the cooling
filler cap permits air to enter the cooling passages and
system of an engine, the additional capacity of the
the coolant to drain completely from the system.
radiator, hoses, etc. must be added to the capacity of
the basic engine. The capacity of radiators and related
Drain cocks or plugs are located on each side of the 4-
equipment should be obtained from the equipment
53 and 6V cylinder blocks. The 3-53 cylinder block has
a drain cock or plug located on the side of the block
opposite the oil cooler.
Fill Cooling System
IMPORTANT : Drain cocks or plugs on
Before starting an engine, close all of the drain cocks
both sides of the engine must be
and fill the cooling system completely. If the unit has a
opened to drain the engine completely.
raw water pump, it should be primed, since operation
without water may cause impeller failure.
In addition to the drains on the cylinder blocks, the Inline
engines have a drain cock located on the bottom of the
COOLING SYSTEM CAPACITY CHART
oil cooler housing. The V-type engines have two drain
cocks that must be opened when draining the system.
Radiators, etc., that do not have a drain cock, are
drained through the oil cooler housing drain.
To insure that all of the coolant is drained completely
from an engine, all cooling system drains should be
opened. Should any entrapped water in the cylinder
Start the engine and, after normal operating
block or radiator freeze, it will expand and may cause
temperature has been reached, allowing the coolant to
damage. When freezing weather is expected, drain all
expand to its maximum, check the coolant level. The
engines not adequately protected by antifreeze.