Coolant Level

is an indication that the corrosion inhibitor has lost its

Any unusual increase in the amount of coolant needed to

effectiveness. Rusty cooling water or antifreeze solution

bring the level up to standard height should be

should be drained, discarded, and replaced at the first

investigated It should be corrected by the operator or

opportunity. Rust in the radiator, rusty coolant, or coolant

reported by him as a possible indication of trouble

containing oil or other foreign matter also indicates the

developing in the system.

need for preventive cleaning of the system.

e. Overfilling (fig 2-19) If the radiator is continually

filled above specified level or when the engine is not up to

2-20.

Coolant Level

minimum safe operating temperature, any changes in the

level or the quantity of coolant additions will be of little

a. Coolant Level Checking. The level of coolant in

value as an indicator of cooling system condition. Both

the radiator is the starting point for proper cooling system

water and antifreeze expand when heated (para 2-27), and

preventive maintenance. Coolant level should be checked

if there is not enough air space left in the radiator for this

accurately as well as frequently for three separate

expansion, some coolant will be lost through overflow.

purposes: (1) to make sure the system always contains

Overfilling the radiator while using water results in dilution

enough coolant, (2) as a guide to cooling system condition;

and weakening of corrosion inhibitor solution (para 2-32).

and (3) to avoid overfilling.

Unnecessary additions of water increase water scale

deposits which interfere with removal of heat from the

b. Coolant Shortage. It is important to make sure

engine. Overfilling also wastes antifreeze and when a

that the system contains a sufficient quantity of coolant at

system containing antifreeze is overfilled with water, it may

all times, if the most common cause of overheating is to

lead to a freeze-up.

be avoided. Low coolant level may prevent proper

circulation, especially at lower engine speeds. At higher

engine speeds, low coolant level allows a large volume of

air to become mixed with the liquid. Air bubbles in the

coolant not only reduce the capacity of the coolant to carry

away heat, but also promote rapid rust formation and

corrosion, and may cause excessive foaming and coolant

loss out the overflow pipe. In any case, coolant shortage

leads to overheating, operating difficulties, and engine

damage (para 2-18b). Having sufficient cool ant in the

system at all times is especially important in military

operations, due to the necessity of being constantly

prepared for all possible operating emergencies.

Figure 2-19. Loss of coolant through expansion by heat

c. Coolant Level as Indicator of Cooling System

when radiator is overfilled.

Condition. The second reason for checking coolant level

is less generally understood. In the military vehicle cooling

Operator's Responsibility.

Coolant level

system equipped with a radiator pressure cap, very little

preventive maintenance services by the operator consist

coolant should be lost through evaporation or from any

not only of keeping sufficient coolant in the system at all

other cause if the system is clean, leakproof, and in proper

times without overfilling, but also include maintaining a

working order. Therefore, any unusual coolant loss over a

standard level at a specified temperature to provide a

period of normal operation may indicate an improper

sensitive indication of any hidden trouble that might

condition within the system, any such condition should be

develop in the system.

located and corrected before it causes serious trouble.

2-21.

Preventive Cleaning

d. Standard Coolant Level Maintenance The

operator can assist greatly in the early detection of

a. General The cooling system should always be

irregular conditions inside the cooling system by keeping

cleaned following the draining of rusty or contaminated

track of the quantities of coolant necessary to maintain the

coolant before fresh coolant is installed. Neglect of

standard height of liquid level in the radiator as specified

cleaning at this time may result In overheat-

for his equipment. The coolant level should always be

checked at approximately the minimum safe operating

temperature, if possible, since the level rises as the engine

warms up and falls as the engine cools down (para 2-27).

2-15