TM 5-3810-300-24&P-3
COOLING SYSTEM 5
be added to the capacity of the basic engine. The
Flush Cooling System
capacity of the radiator and related equipment should be
If a coolant filter is used and properly maintained the
obtained from the equipment supplier, or the capacity of
cooling system need not be flushed. Otherwise the
a particular cooling system may be determined by filling
cooling system should be flushed each spring and fall.
the system with water, then draining and measuring the
The flushing operation cleans the system of antifreeze
amount required.
solution in the spring and removes the summer rust
inhibitor in the fall, preparing the cooling system for a
Drain Cooling System
new solution.
The flushing operation should be
Drain the coolant by opening the drain cocks in the water
performed as follows:
outlet elbow, oil cooler housing, the fresh water pump,
1. Drain the previous season's solution from the
the radiator and, on certain engines, the water hole cover
unit.
located on the blower side toward the rear of the cylinder
2. Refill the cooling system with soft, clean water.
block. Components of the cooling system that do not
If the engine is hot, fill slowly to prevent rapid
have a drain cock, are drained through the oil cooler
cooling and distortion of the engine castings.
housing drain cock.
3. Start the engine and operate it for 15 minutes to
thoroughly circulate the water.
Remove the cooling system filler cap to permit the
4. Drain the cooling system completely.
coolant to drain completely from the system.
5. Refill the system with the solution required for
the coming season.
To ensure that all of the coolant is drained completely
from a engine, all cooling system drains should be
Cooling System Cleaners
opened. Should any water that may be trapped in the
If the engine overheats and the fan belt tension and
cylinder block or radiator freeze, it will expand and may
water level are satisfactory, it will be necessary to clean
cause damage. When freezing weather is expected,
and flush the entire cooling system. Scale formation
drain a unit not adequately protected by antifreeze.
should be removed by using a quality descaling solvent.
Leave all drain cocks open until refilling the cooling
Immediately after using the solvent, neutralize the
system.
system with a neutralizer. It is important that the
directions printed on the container of the descaling
Fill Cooling System
solvent be thoroughly read and followed.
Before starting the engine, close all of the drain cocks
and fill the cooling system with water. The use of clean,
After the solvent and neutralizer have been used,
soft water will eliminate the need for descaling solutions
completely drain the engine and radiator and flush it with
to clean the cooling system. A hard, mineral-laden water
clean water. Then, fill the system with the proper cooling
should be made soft by using water softener chemicals
solution.
before it is poured into the cooling system. These water
softeners modify the minerals in the water and greatly
CAUTION: Whenever water is added to a
reduce or eliminate the formation of scale.
hot engine, it must be done slowly to avoid
rapid cooling which may cause distortion
Start the engine and, after the normal operating
and possible cracking of engine castings.
temperature has been reached, allowing the coolant to
Reverse Flushing
expand to its maximum, check the coolant level. The
After the engine and radiator have been thoroughly
coolant level should be within 2" of the top of the filler
cleaned, they should be reverse-flushed. The water
neck.
pump should be removed and the radiator and engine
reverse-flushed separately to prevent dirt and scale
Should a daily loss of coolant be observed, and there are
deposits clogging the radiator tubes or being forced
no apparent leaks, there is a possibility of gases leaking
through the pump. Reverse-flushing is accomplished
past the cylinder head water seal rings into the cooling
with hot water, under air pressure, being forced through
system. The presence of air or gases in the cooling
the cooling system in a direction opposite to the normal
system may be detected by connecting a rubber tube
flow of coolant, thus loosening and forcing the scale
from the overflow pipe to a water container. Bubbles in
deposits out.
the water in the container during engine operation will
indicate this leakage. Another method for observing
entrained air in the cooling system is by inserting a
transparent tube in the water outlet line.
Page 303
