Keel Cooling System
The keel cooling system is similar to the heat exchanger system, except that the coolant temperature is reduced in the
keel cooler. In this system, the coolant is drawn by the circulating pump from the bottom of the expansion tank through
the engine oil cooler. From the cooler the flow is the same as in the other systems. Upon leaving the thermostat
housing, the coolant is by-passed directly to the bottom of the expansion tank until the engine operating temperature,
controlled by the thermostat, is reached. As the engine temperature increases, the coolant is directed to the keel cooler,
where the temperature of the coolant is reduced before flowing back to the expansion tank.
ENGINE COOLING SYSTEM MAINTENANCE
The function of the engine coolant is to absorb the heat, developed as a result of the combustion process in the cylinders,
from the component parts such as exhaust valves, cylinder liners and pistons which are surrounded by water jackets. In
addition, the heat absorbed by the oil is also removed by the engine coolant in the oil-to-water oil cooler.
For the recommended coolant, refer to Engine Coolant.
Cooling System Capacity
The capacity of the basic engine cooling system (cylinder block, head, thermostat housing and oil cooler housing) is
shown in Table I.
To obtain the complete amount of coolant in the cooling system of an engine, the additional capacity of the radiator,
hoses, etc. must be added to the capacity of the basic engine. The capacity of radiators and related equipment should
be obtained from the equipment supplier.
Fill Cooling System
Before starting an engine, close all of the drain cocks and fill the cooling system completely. If the unit has a raw water
pump, it should be primed, since operation without water may cause impeller failure.
COOLING SYSTEM CAPACITY CHART
Start the engine and, after normal operating temperature has been reached, allowing the coolant to expand to its
maximum, check the coolant level. The coolant level should be within 2"of the top of the filler neck.
Should a daily loss of coolant be observed, and there are no apparent leaks, there is a possibility of gases leaking past
the cylinder head water seal rings into the cooling system. The presence of air or gases in the cooling system may be
detected by connecting a 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 method for observing air in the cooling system is by inserting
a transparent tube in the water outlet line.
Drain Cooling System
The engine coolant is drained by opening the cylinder block and radiator (heat exchanger) drain cocks and removing the
cooling system filler cap. Removal of the filler cap permits air to enter the cooling passages and 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 block opposite the oil cooler.
IMPORTANT: Drain cocks or plugs on both sides of the engine must be opened to drain the
In addition to the drains on the cylinder blocks, the In-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