TM 5-3895-346-14
ENGINE OVERHAUL
COOLING SYSTEM
ENGINE COOLING SYSTEM MAINTENANCE
Engine Coolant
The function of the engine coolant is to absorb the heat, developed as a result of the combustion process in the
cylinders, from 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 when oil-to-water
oil coolers are used. Refer to Fuel and Oil Specifications for coolant recommendations.
Cooling System Capacity
The capacity of the basic engine cooling system (cylinder block, head, thermostat housing, and oil cooler
housing) is shown in Table 1.
To obtain the complete amount of coolant in the cooling system of a unit, the additional capacity of the radiator,
hoses, etc. must be added to the capacity of the basic engine. The capacity of the radiator and related
equipment should be obtained from the equipment supplier, or the capacity of a particular cooling system may
be determined by filling the system with water, then draining and measuring the amount required.
TABLE 1
COOLING SYSTEM CAPACITY
(BASIC ENGINE)
ENGINE
CAPACITY
GALLONS
LITRES
4-53
2-1/4
8.5
Fill Cooling System
Before starting the engine, close all of the draincocks and fill the cooling system with water. The use of clean,
soft water will eliminate the need for descaling solutions to clean the cooling system. A hard mineral-laden
water should be made soft by using water softener chemicals before it is poured into the cooling system. These
water softeners modify the minerals in the water and greatly reduce or eliminate the formation of scale. Refer
to Engine Coolant.
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 two inches of the filler neck.
Excessive amounts of air in the cooling system may hinder the flow of water due to pump cavitation or result in
hot spots when air collects at low velocity points in the water passages. Therefore, whenever the cooling
system is filled or makeup water is added, the air must be thoroughly vented from the system. The thermostat
housing on the Series 53 engines provides a venthole to release the air to the atmosphere while the cooling
system is being filled. In addition, the cooling system should be vented at the time normal operating
temperature is reached after starting the engine and again after the engine has been in operation for 30 to 45
minutes.
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.
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