TM 5-685/NAVFAC MO-912
COOLING SYSTEMS AND COOLANTS
flushing or cleaning the system with compound
when necessary. Engines used in Arctic regions are
The coolant used in diesel engines usually consists
covered in paragraph D-4.
of a mixture of ethylene glycol antifreeze, corrosion
a. Testing antifreeze. Perform tests to verify
inhibitor, and fresh water. When the engine is used
freeze protection and reserve alkalinity.
in an extremely cold area, such as Arctic regions, a
(1) Test for freeze protection using the combi-
special antifreeze mixture is used. Specifications re-
nation antifreeze and battery tester, stock number
lated to the mixtures are as follows:
6630-00-105-1418. Instructions for using the
Antifreeze, Ethylene glycol
tester are included with it.
Antifreeze, Arctic- type
(2) Test for reserve alkalinity (corrosion protec-
The specification for cooling system cleaning compound is
tion) using the reserve alkalinity test kit, stock
(3) Cooling systems with freeze protection be-
D-2. Engine water treatment.
low - 7 degrees F ( -22 degrees C) that fail the
The prime consideration in a closed water cooling
reserve alkalinity test may be replenished with cor-
system is proper water treatment to ensure no cor-
rosion inhibitor, stock number 6850-00-753-4967.
rosion or scale occurs during static or dynamic en-
Replenishment is a one-time service. If the reserve
alkalinity test is failed again, replace the coolant. If
a. Acceptable conditions. In most modern diesel
the system passes the test, record the date.
engines the following cooling water conditions are
b. Inspecting coolant.
(1) Inspect the coolant visually for cleanliness.
(1) pH 8.5 to 10
Obtain a coolant sample and place it in a clean glass
(2) Chlorid e and Sulfate
container. After allowing about five minutes for set-
(3) Total Dissolved Solids
tling, examine the sample for contamination (rust,
(4) Total Hardness
foreign particles, and/or sediment). The sample may
b. Softened water. If possible softened water
should be utilized to reduce the total hardness level
have some color (same color as original antifreeze)
of the engine cooling loop. The use of softened water
and should be clear.
will increase engine performance by reducing the
(2) Examine the sample to determine the type
precipitation of calcium and magnesium at elevated
and quantity of contamination. Rust, a chemical
temperature conditions, ensuring higher heat
combination of iron, water, and air, is frequently
found. The presence of rubber particles usually in-
c. Antifreeze. Typically, engine cooling systems in-
dicates deterioration of hoses. Replacement hoses
corporate antifreeze solutions which inhibit scale
may be indicated. Sediment may be caused by im-
and protect the cooling system when temperatures
purities in the water used in the coolant. Contami-
are encountered below freezing. Ethylene glycol
nants in the coolant can clog a radiator or heat
mixed with a corrosion inhibitor such as triazoles
exchanger and cause engine and generating system
form an inhibiting film on metal surfaces that acts
as a barrier in the corrosion process. The following
c. Cleaning the system. Clean the cooling system
concentration curves should be utilized when add-
whenever the coolant is drained. Usually the sys-
ing glycol solutions to engine cooling system.
tem requires nothing more than thorough flushing
d. Concentration. As indicated by the chart the
out with fresh water. Refer to the engine manufac-
concentration should exceed 30 percent. If more
turer's literature for instructions. If any part of the
than 60 percent of solution is added two effects will
system is rusted or partially clogged, it is necessary
be realized; first a decrease in heat transfer rates,
to use cooling system cleaning compound and condi-
second a lowering of the system freeze protection.
tioner, stock number 6850-00-598-7328. Do not use
D-3. Cooling system maintenance.
the compound as a routine maintenance procedure.
Instructions for using the compound are included
Maintenance consists of periodically testing the an-
tifreeze, inspecting the coolant for cleanliness, and