DETROIT DIESEL 53
Fuel, Oil and Coolant Specifications 13.3
ENGINE COOLANT
dissolved solids. Water, within the limits specified on
Engine coolant is considered as any solution which is
Tables I and 2, Figure A, is satisfactory as an engine
circulated through the engine to provide the means for
coolant when proper inhibitors are added.
heat transfer from the various engine components. In
general, water containing various materials in solution is
CORROSION INHIBITORS
used for this purpose.
A corrosion inhibitor is a water soluble chemical
The function of the coolant is basic in the design and the
compound which protects the metallic surfaces of the
successful operation of the engine and must be carefully
cooling system against corrosive attack. Some of the
selected and properly maintained.
more commonly used corrosion inhibitors are
COOLANT REQUIREMENTS
chromates, borates, nitrates, nitrites and soluble oil.
Depletion of all types of inhibitors occur through normal
A suitable coolant solution must meet the following five
operation and therefore strength levels must be
basic requirements:
maintained by the addition of inhibitors at prescribed
1.
Provide for adequate heat transfer.
intervals.
2.
Provide a corrosion resistant environment within
CHROMATES: Sodium chromate and potassium
the cooling system.
dichromate are two of the best and more commonly
3.
Prevent formation of scale or sludge deposits in
used water system corrosion inhibitors. Care should be
the cooling system.
exercised in handling these materials due to their toxic
4.
Be compatible with the cooling system hose and
nature.
seal materials.
Chromate inhibitors should not be used in ethylene
5.
Provide adequate freeze protection during cold
glycol antifreeze solutions.
Chromium hydroxide,
weather operation.
commonly called "green slime", can result from the use
Normally requirements 1 through 4 are satisfied by
of chromate inhibitors with permanent type antifreeze.
combining a suitable water with reliable inhibitors. When
This material deposits on the cooling system passages,
operating conditions dictate the need for freeze
reducing the heat transfer rate and will result in engine
protection, a solution of suitable water and an ethylene
overheating. Engines which have operated with a
glycol type antifreeze containing adequate inhibitors will
chromate inhibited water must be chemically cleaned
provide a satisfactory coolant.
before the addition of ethylene glycol type antifreeze. A
WATER
commercial heavy duty descaler should be used in
Any water, whether of drinking quality or note, will
accordance with the manufacturer's recommendation for
produce a corrosive environment in the cooling system.
this purpose.
Also, scale deposits may form on the internal surfaces
SOLUBLE OIL:
Soluble oil has been used as a
of the cooling system due to the mineral content of the
corrosion inhibitor for many years. It has, however,
water. Therefore, water selected as a coolant must be
required very close attention relative to the
properly treated with inhibitors to control corrosion and
concentration level due to adverse effects on heat
scale deposition.
transfer if the concentration exceeds 1% by volume.
To determine if a particular water is suitable for use as a
For example:
1 1/4% of soluble oil in the cooling
coolant when properly inhibited, the following
system increases fire deck temperatures 6% and a 2
characteristics must be considered. The concentration
1/2% concentration raises fire deck temperature up to
15%. Soluble oil is not recommended as a corrosion
dissolved solids. These materials are objectionable for
inhibitor.
a number of reasons: chlorides and/or sulfates will
NONCHROMATES:
accelerate corrosion, while hardness (percentage of
Nonchromate inhibitors (borates, nitrates, nitrites, etc.)
magnesium and calciumn present) will cause deposits of
provide corrosion protection in the cooling system with
scale. Total dissolved solids may cause scale deposits,
the basic advantage that they can be used with either
sludge deposits, corrosion or a combination of these.
water or a water and ethylene glycol solution.
Chlorides, sulfates, magnesium and calcium are among
but not necessarily all the materials which make up
1972 General Motors Corp.
August, 1972
SEC. 13.3 Page 3
