cooler. From the cooler the flow is the same as in the
Keel Cooling System
other systems. Upon leaving the thermostat housing,
the coolant is by-passed directly to the bottom of the
The keel cooling system is similar to the heat
expansion tank until the engine operating tempera-
exchanger system, except that the coolant temperature
ture, controlled by the thermostat, is reached. As the
is reduced in the keel cooler. In this system, the
engine temperature increases, the coolant is directed to
the keel cooler, where the temperature of the coolant is
bottom of the expansion tank through the engine oil
reduced before flowing back to the expansion tank.
ENGINE COOLING SYSTEM MAINTENANCE
S t a r t the engine and, after normal operating
temperature has been reached, allowing the coolant to
expand to its maximum, check the coolant level. The
The function of the engine coolant is to absorb the
coolant level should be within 2" of the top of the
heat, developed as a result of the combustion process
in the cylinders, from the component parts such as
Should a daily loss of coolant be observed, and there
surrounded by water jackets. In addition, the heat
are no apparent leaks, there is a possibility of gases
absorbed by the oil is also removed by the engine
leaking past the cylinder head water seal rings into the
coolant in the oil-to-water oil cooler.
cooling system. The presence of air or gases in the
cooling system may be detected by connecting a
For the recommended coolant, refer to Engine Coolant.
rubber tube from the overflow pipe to a water
container. Bubbles in the water in the container during
engine operation will indicate this leakage. Another
Cooling System Capacity
method for observing air in the cooling system is by
inserting a transparent tube in the water outlet line.
The capacity of the basic engine cooling system
(cylinder block, head, thermostat housing and oil
cooler housing) is shown in Table 1.
Drain Cooling System
To obtain the complete amount of coolant in the
The engine coolant is drained by opening the cylinder
cooling system of an engine, the additional capacity of
block and radiator (heat exchanger) drain cocks and
the radiator, hoses, etc. must be added to the capacity
removing the cooling system filler cap. Removal of the
of the basic engine. The capacity of radiators and
filler cap permits air to enter the cooling passages and
related equipment should be obtained from the
the coolant to drain completely from the system.
Drain cocks or plugs are located on each side of the
4-53 and 6V cylinder blocks. The 3-53 cylinder block
has a drain cock or plug located on the side of the
Fill Cooling System
block opposite the oil cooler.
Before starting an engine, close all of the drain cocks
IMPORTANT: Drain cocks or plugs on both sides
and fill the cooling system completely. If the unit has a
of the engine must be opened to drain the
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 In-
COOLING SYSTEM CAPACITY CHART
line engines have a drain cock located on the bottom
of the 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
block or radiator freeze, it will expand and may cause
damage. When freezing weather is expected, drain all
engines not adequately protected by antifreeze. Leave