DETROIT DIESEL 53
Fuel, Oil and Coolant Specifications
13.3
ENGINE COOLANT
Engine coolant is considered as any solution which is
sludge deposits, corrosion or a combination of these.
circulated through the engine to provide the means for
Chlorides, sulfates, magnesium and calcium are
heat transfer from the various engine components. In
among but not necessarily all the materials which
general, water containing various materials in solution
make up dissolved solids. Water, within the limits
is used for this purpose.
specified in Tables 1 and 2, Figure A, is satisfactory
as an engine coolant when proper inhibitors are
The function of the coolant is basic in the design and
added.
the successful operation of the engine and must be
carefully selected and properly maintained.
CORROSION INHIBITORS
COOLANT REQUIREMENTS
A suitable coolant solution must meet the following
A corrosion inhibitor is a water soluble chemical
five basic requirements:
compound which protects the metallic surfaces of the
cooling system against corrosive attack. Some of the
1. Provide for adequate heat transfer.
more commonly used corrosion inhibitors are chro-
mates, borates, nitrates, nitrites and soluble oil.
2. Provide a corrosion resistant environment within the
Depletion of all types of inhibitors occur through
cooling system.
normal operation and therefore strength levels must
be maintained by the addition of inhibitors at
3. Prevent formation of scale or sludge deposits in the
prescribed intervals.
cooling system.
CHROMATES: Sodium chromate and potassium
4. Be compatible with the cooling system hose and seal
dichromate are two of the more commonly used water
materials.
system corrosion inhibitors. However, the restrictive
use of these materials, due to ecology considerations,
5. Provide adequate freeze protection during cold
has de-emphasized their use in favor of non-
weather operation.
chromates. Care should be exercised in handling these
materials due to their toxic nature.
Normally requirements 1 through 4 are satisfied by
combining a suitable water with reliable inhibitors.
Chromate inhibitors must not be used in ethylene
When operating conditions dictate the need for freeze
glycol antifreeze solutions. Chromium hydroxide,
protection, a solution of suitable water and an ethylene
commonly called "green slime", can result from the
glycol type antifreeze containing adequate inhibitors
use of chromate inhibitors with permanent type
will provide a satisfactory coolant.
antifreeze. This material deposits on the cooling
system passages, reducing the heat transfer rat,. and
will result in engine overheating. Engines which have
WATER
operated with a chromate inhibited water must be
chemically cleaned before the addition of ethylene
Any water, whether of drinking quality or not, will
glycol type antifreeze. A commercial heavy duty de-
produce a corrosive environment in the cooling system.
scaler should be used in accordance with the
Also, scale deposits may form on the internal surfaces
manufacturer s recommendation for this purpose.
of the cooling system due to the mineral content of the
water. Therefore, water selected as a coolant must be
SOLUBLE OIL: Soluble oil has been used as a
properly treated with inhibitors to control corrosion
corrosion inhibitor for many years. It has, however,
and scale deposition.
required very close attention relative to the concentra-
To determine if a particular water is suitable for use
tion level due to adverse effects on heat transfer if the
as a coolant when properly inhibited, the following
concentration exceeds 1% by volume. For example:
characteristics must be considered. The concentration
1-1/4% of soluble oil in the cooling system increases
fire deck temperatures 6% and a 2-1/2% concentration
dissolved solids. These materials are objectionable for
raises fire deck temperature up to 15%. Soluble oil
a number of reasons: chlorides and/or sulfates will
must not be used as a corrosion inhibitor.
accelerate corrosion, while hardness (percentage of
magnesium and calcium present) will cause deposits of
NON-CHROMATES: Non-chromate inhibitors (bo-
rates, nitrates, nitrites, etc.) provide corrosion
scale. Total dissolved solids may cause scale deposits,
SEC. 13.3 Page 3
April. 1974
