Cooling System - MCi MC8 Crusader Maintenance Manual

M 1 Yi?RMx•
MC-8
IVIAIN I tNANt;t
. MANUAL
[ -.c,
____=c6_-
1-'---------------''---
DA TE
~J_u----#1
Y~,_1_9_73 _ _ _ ]
COOLING SYSTEM
COOLING SYSTEM
DESCRIPTION
_ E_ngine coolant is considered as any solution which
1s circulated through the engine to provide the means
for heat transfer from various engine components. In
general, water containing various materials in
solution is used for this purpose.
The functiofl of the coolant is basic in the design
and the successful operation of the engine and must
be carefully selected and properly maintained.
COOLANT REQUIREMENTS
A suitable coolant solution must meet the
following five basic requirements.
I. Provide for adequate heat transfer.
2. Provide a corrosion resistant environment within
the cooling system.
3. Prevent formation of scale or sludge deposits in
the cooling system.
4. Be compatible with the cooling system hose and
seal materials.
5. Provide adequate freeze protecting during cold
weather operation.
Normally, requirements I through 4 are satisfac-
tory by combining a suitable water with reliable
inhibitors. When operating conditions dictate the
need for freeze protection, a solution of suitable
water and an ethylene glycol type antifreeze con-
taining adequate inhibitors will provide a satisfactory
coolant.
WATER
Any water, whether of drinking quality or not, will
produce a corrosive environment in the cooling
system. Also, scale deposits may form on the internal
surfaces of the cooling system due to the mineral con-
tent of the water. Therefore, water selected as a
coolant must be properly treated with inhibitors to
control corrosion and scale deposition.
To determine if a particular water is suitable for
use as a coolant when properly inhibited, the
following characteristics must be considered. The
concentration of
(I)
chlorides, (2) sulfates, (3) total
hardness and (4) dissolved solids. These materials
are objectionable for a number of reasons: chlorides
and/or sulfates will accelerate corrosion, while hard-
ness (percentage of magnesium and calcium present)
will cause deposits of scale. Total dissolved solids
may cause scale deposits, sludge deposits, corrosion
or a combination of these. Chlorides, sulfates,
magnesium and calcium are among but not necessary
all the materials which make up dissolved solids.
Water within the limits specified on Tables 1 and 2,
Illustration A, is satisfactory as an engine coolant
when proper inhibitors are added.
CORROSION INHIBITORS
A corrosion inhibitor is a water soluble compound
which protects the metallic surfaces of the cooling
system against corrosive attack. Some of the more
commonly used corrosion inhibitors are chromates,
borates, nitrites and soluble oil. Depletion of all
types of inhibitors occur through normal operation
and therefore, strength levels must be maintained by
the addition of inhibitors at prescribed intervals.
CHROMA TES
Sodium chromate and potassium dichromate are
two of the best and more commonly used water
system corrosion inhibitors. Care should be exercised
in handling these materials due to their toxic nature.
Chromate inhibitors should not be used in ethylene
glycol antifreeze solutions. Chromium hydroxide,
commonly called "green slime" can result from the
use of chromate inhibitors with permanent type an-
tifreeze. This material deposits on the cooling system
passages, reducing the heat transfer rate and will
result in engine overheating. Engines which have
operated with a chromate inhibitor water must be
chemically cleaned before the addition of ethylene
glycol type antifreeze. A commercial heavy duty de-
scaler should be used in accordance with the
manufacturer's recommendation for this purpose.
SOLUBLE OIL
Soluble oil has been used as a corrosion inhibitor
for many years. It has, however, required very close
attention relative to the concentration level due to
adverse affects on heat transfer if the concentration
exceeds l % by volume. For example: 1-1 /4% of
soluble oil in the cooling system increases fire deck
temperature 6% and a 2-1 /2% concentration raises
fire deck temperature up to
15% .
Soluble oil is not
recommended as a corrosion inhibitor.
NON-CHROMATES
Non-chromate inhibitors (borates, nitrates, etc.)
provide corrosion protection in the cooling system
with the basic advantage that they can be used with
either a water and ethylene glycol solution.
INHIBITOR SYSTEMS
An inhibitor system is considered as a combination
of chemical compounds which provides corrosion
protection and water softening ability. Corrosion
protection has been discussed earlier under the sec-
tion of "Corrosion Inhibitors". The water softening
ability deters formation of mineral deposits. Inhibitor
systems c1re available in various forms such as coolant
filter elements, liquid and dry inhibitor additives and
as integral part of permanent antifreeze.