TM 5-3895-359-14&P
Flush Cooling System
Cooling System Capacity
If a coolant filter is used and properly maintained, the
cooling system need not be flushed. Otherwise, the
The capacity of the basic engine cooling system
cooling system should be flushed each spring and fall.
(cylinder block, head, thermostat housings and oil cooler
housing) is 3.5 gallons (13.2) litres.
The flushing operation cleans the system of antifreeze
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
performed as follows:
Drain the coolant by opening the drain cocks in the
water outlet elbow, oil cooler housing, the fresh water
1. Drain the previous season's solution from the unit.
pump and the radiator. Components of the cooling
system that do not have a drain cock, are drained
2. Refill the cooling system with soft, clean water. If the
through the oil cooler housing drain cock.
engine is hot, fill slowly to prevent rapid cooling and
distortion of the engine castings.
Remove the cooling system filler cap to permit the
3. Start the engine and operate it for 15 minutes to
coolant to drain completely from the system.
thoroughly circulate the water.
To ensure that all of the coolant is drained completely
4. Drain the cooling system completely.
from an engine, all cooling system drains should be
opened. Should any water that may be trapped in the
5. Refill the system with the solution required for the
cylinder block or radiator freeze, it will expand and may
coming season.
cause damage. When freezing weather is expected,
drain a unit not adequately protected by antifreeze.
Leave all drain cocks open until refilling the cooling
Cooling System Cleaners
system.
If the engine overheats and the fan belt tension and
water level are satisfactory, it will be necessary to clean
and flush the entire cooling system. Scale formation
Fill Cooling System
should be removed by using a quality descaling solvent.
Immediately after using the solvent, neutralize a system
Before starting the engine, close all of the drain cocks
with a neutralizer. It is important that the directions
and fill the cooling system with water. The use of clean,
printed on the container of the descaling solvent be
soft water will eliminate the need for descaling solutions
thoroughly read and followed.
to clean the cooling system. A hard, mineral-laden
water should be made soft by using water softener
After the solvent and neutralizer have been used,
chemicals before it is poured into the cooling system.
completely drain the engine and radiator and flush it
These water softeners modify the minerals in the water
with clean water. Then fill the system with the proper
and greatly reduce or eliminate the formation of scale.
cooling solution.
Start the engine and, after normal operating
CAUTION:
temperature has been reached, allowing the coolant to
Whenever water is added to a hot
expand to its maximum, check the coolant level. The
engine, it must be done slowly to
coolant level should be within 2 " of the top of the filler
avoid rapid cooling which may cause
neck.
distortion and possible cracking of
engine castings.
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
Reverse- Flushing
cooling system. The presence of air or gases in the
After the engine and radiator have been thoroughly
cooling system may be detected by connecting a rubber
cleaned, they should be reverse-flushed. The water
tube from the overflow pipe to a water container.
pump should be removed and the radiator and engine
Bubbles in the water in the container during engine
reverse-flushed separately to prevent dirt and scale
operation will indicate this leakage. Another method for
deposits clogging the radiator tubes or being forced
observing trapped air in the cooling system is by
through the pump. Reverse-flushing is accomplished
inserting a transparent tube in the water outlet line.
10-6-3
