Inhibitor for Water.

b. Inhibitor in Antifreeze Since inhibitors are

coolant is lost. Finally, coolant circulation stops, and

cooling falls completely This means that operating an

included in antifreeze compounds (para 2-32c), no

engine with the coolant boiling for even a short length of

inhibitors of any kind should be added to fresh antifreeze

time may be actually driving that engine to destruction.

solutions. However, corrosion inhibitors may be weakened

by use in the cooling system. Therefore, it is important to

c. Overcooling Difficulties. Although less sudden in

add an inhibitor to reclaimed antifreeze solutions that are

effect than overheating, overcooling may be equally

to be used a second winter (para 2-32g).

dangerous to the engine.

Low engine operating

temperature, especially during freezing weather, results in

CAUTION

excessive fuel consumption, dilution of engine oil by

unburned fuel, and formation of sludge from condensation

Do not add any more or any less Inhibitor than

of water in cylinders and crankcase. Lubrication failure

specified in current directives.

may follow sludge formation and lead to serious engine

damage. Burned fuel vapors also mix with water in the

c. Inhibitor for Water.

Corrosion protection is

crank case and form corrosive acids which attack engine

particularly important during warm-weather driving when

parts.

water is used as coolant, since there is more air in the

coolant and more rusting in the system. In very cold

d. Temperature Gage Observation

weather, control of coolant circulation by the thermostat

(1) To avoid overheating difficulties, the operator

may reduce flow into the radiator to only a few gallons per

must be constantly alert to see that the temperature gage

minute and very little air is driven into the coolant. In hot

does not exceed the maximum safe operating temperature

weather, with thermostat wide open, the flow Into the

specified for the vehicle. Whenever the gage registers

radiator at high engine speeds may increase to 100

above this temperature, the vehicle should be halted, the

gallons a minute or more in some engines. The resulting

engine stopped, and the cause investigated and corrected

increase in coolant aeration, together with a higher metal

before further operation is attempted. It is also important

and coolant temperature, greatly speeds up the rate of

to watch the gage for a sudden rise in temperature during

rusting (para 2-16b). Installation of inhibitor with water

engine warm-up as an indication of defective cooling.

coolant is a most essential preventive maintenance

service.

(2) To prevent overcooling difficulties, keep any

necessary warm-up period before operation as short as

d. Rust Prevention vs Cleaning or Replacement.

possible, and avoid continued operation of the vehicle if

The time and effort required for adding Inhibitor to a filling

the temperature gage does not reach the minimum

of fresh water or for adding reinhibitor to reclaimed

operating temperature specified for the vehicle.

antifreeze solution is only a fraction of what is necessary

for cleaning a rusty system in which corrosion-prevention

(3) When checking for either overheating or

services have been neglected, or for replacing a clogged

overcooling, the possibility of a false temperature

or corroded radiator. However, if restriction of flow of

indication from a defective gage should not be overlooked.

inhibitor is suspected, then flo-tester (3, fig. 2-1) should be

utilized to determine amount of restriction.

(4) Prevention of both overheating and over cooling

difficulties thus requires temperature gage observations

2-18.

Coolant Operating Temperature

both before and during operation. It also requires a

positive knowledge by the driver or engine operator, of the

a. General. Frequent observation of the engine

highest and lowest safe operating temperature specified

temperature gage during operation is a primary preventive

for the particular engine.

maintenance service for detecting overheating or

overcooling of the engine in the first stages, before serious

2-19.

Coolant Examination

trouble develops.

Another most important cooling system preventive

b. Overheating difficulties. Excessively high engine

maintenance service is examination of the coolant for

temperatures not only cause "knock" and loss of power,

color and cleanliness, at least weekly. This can be

but also will result in damage to bearings and other moving

conveniently done during coolant level inspection by

parts. Cylinder heads and engine blocks are often warped

drawing a sample into a suitable hydrometer or antifreeze

and cracked by terrific strains set up in the overheated

tester In a system that was reasonably clean when the

metal, especially when coolant is added immediately

coolant was originally installed, the appearance of rust in

afterward without allowing the engine to cool. Overheating

the radiator or in the coolant.

first causes coolant boiling. If the vehicle is operated with

boiling coolant, steam pressure forces large quantities of

coolant out of the system through the radiator overflow

pipe. More violent boiling then occurs, and still more

2-14