The performance requirements of automobile antifreeze became more severe during the
1980’s and 1990’s. The reduction of the overall mass of vehicles to improve fuel
economy entailed extensive use of light materials such as aluminum and plastics for the
construction of engine and cooling system parts. Many of the engines used today in
most forklifts use aluminum heads and, in some cases, aluminum engine blocks. The
volume of antifreeze used was also drastically reduced to further reduce weight,
subjecting the antifreeze to high rates of flow, high temperatures and significant metalto-
coolant heat fluxes. Today’s smaller, efficient and powerful engines dissipate more
heat, requiring that the antifreeze keep the heat exchange surfaces in clean condition. In
addition, corrosion, which in itself is of concern, can also result in heavy corrosion
deposits that impede heat transfer.
Modern antifreeze provides year-round protection of the cooling system: It prevents
freeze up in winter and boilover in summer. It provides protection from rust and
corrosion and does not harm rubber hoses and plastics. A desirable antifreeze should
not corrode metal parts, attack rubber, become viscous at low temperatures, or
evaporate readily at the ordinary engine operating temperature. It should be chemically
stable, a good conductor of heat, and a poor conductor of electricity (which causes
There are basically three types of antifreeze, and all of them are made from 95% or
more ethylene glycol. That means that all three types will mix without causing the
buildup of sludge in the Cooling System or clogging your radiator. But mixing the
various antifreeze versions can reduce the supplemental coolant additive package
(SCA) to its lowest level of corrosion protection. Engine Coolant should be Anti-
Freeze mixed 50/50 (or close to it) with water in order to achieve the highest degree of
protection against freezing and boil over and it also protects both the engine and heat
exchanger (radiator, heater core, or intercooler) from corrosion. Generally if the engine
coolant is more than 70 % antifreeze it loses its corrosion protection and heat transfer
capability. CLARK (in particular) DOES NOT APPROVE the use of straight concentrated
antifreeze as engine coolant. The corrosion that we are all worried about is generally
either corrosion of aluminum or corrosion of the lead in the solder of copper-brass
The first, oldest, and most familiar type of antifreeze is known as “Conventional
Green” and is a good general antifreeze with protection for both aluminum and solder.
But it has Inorganic Acid Technology, (IAT) for additives, and tends to get corrosive as
the coolant ages. The standard practice has always been to change your engine coolant
once a year and flush the engine cooling system to get rid of the contamination that has
settled out of the coolant and into the cooling system. If the engine cooling system is
not serviced as recommended you will end up with corroded radiators, corroded engine
parts, overheating problems, and various other engine problems.
The second type of antifreeze is a long life antifreeze and uses DexCool as bases for its
SCA package. The DexCool is orange in color and this additive package is known as
Organic Acid Technology (OAT). The DexCool SCA package deteriorates more
slowly and is less aggressive against aluminum; BUT it is much more corrosive against
the solder in copper brass radiators. A few lift truck manufacturers are using all
aluminum cooling systems so DexCool does not pose problems. But some still use
soldered copper brass radiators, this bring us to a second generation of DexCool known
as Hybrid (HOAT), or G-05. The hybrid (HOAT) G-05 had some of both the IAT and
OAT and is the most prevalent automotive OEM initial fill (yellow in color). There is
also an Asian version of the hybrid (HOAT) G-05 antifreeze that is pink and has some
The third type of antifreeze is known as Pre-Charged Heavy Duty and is the coolant
used in Heavy Diesel engines with a tendency toward liner pitting. It is available as
either conventional IAT (green) or Extended Service OAT which is red in color. It has
an additional “SCA package” of additives that prevent iron corrosion, aluminum
corrosion, and solder corrosion. Also, when it does degrade it is not as aggressive as
the IAT green kind.
Regardless of what antifreeze you are using you still must keep the engine cooling
system filled with non-aerated coolant. Failure to do so will cause overheating
problems and will also cause any contamination in the engine coolant to solidify and
drop out and clog the cooling system.
When the Engine Coolant is low it is recommend to use a manufacturer pre-mixed
50/50 solution that doesn’t require diluting and comes from the factory with de-ionized
water. If a factory pre-mixed solution is not available fill the cooling system with
mineral free water that does not contain any salts, mud, rust, lime, or other
Deteriorated coolant or coolant unsuitable for use in engines having aluminum alloy
components corrodes the surface of the aluminum, known as the aluminum matrix, on
the inner surface of the water chambers. Silicon crystalloids (Si) stick out in the
corrosion layer and increase the corrosive action on the aluminum matrix, this results in
a selective etching of the aluminum matrix in that particular area of the water chamber.
The higher corrosive action of the etched area increases the number and depth of the
corrosion pits, which eventually leads to a fatigue failure of the aluminum matrix
resulting in a crack in the water chamber. The selective etching and ultimate crack will
be initiated in an area of the aluminum matrix that has a higher concentration of stress.
In addition, the deteriorated coolant will also cause corrosion in the solder joints of the
radiator by disassociating the lead from the solder; it may also cause bimetallic
corrosion with any lead-aluminum alloy in the radiator. In either case the end result
will be either cracks or leaks in the soldered joints of the radiator, or decreased cooling
efficiency of the radiator due to restrictions caused by the corrosion.
SOLUTION: Proper Cooling System Maintenance is especially important to replenish the additives
that protect the cooling system from rust, corrosion, pitting, electrolysis and foaming to
aid in the prevention of these issues.
1) The Engine Coolant level and condition be checked at every PM after the
Engine has cooled down:
A.) First check the Coolant Level in the Radiator and make sure the
Radiator is completely filled, if necessary bleed the Cooling System in
accordance with SI-01-818-10.
B.) Then fill the Recovery Bottle so the Coolant Level is between the Cold
and Hot Fill Lines.
2) The Engine Coolant protection and additives be checked at every 1,000
hours or six months of operation. The Engine Coolant System be drained
and flushed, and the coolant changed a minimum of once every 2,000 hours
or one year of operation, maintaining the proper concentration of the
3) In addition most recommend the Radiator Cap be inspected at each
PM, and Pressure Tested a minimum of once every 2,000 hours or one year
of operation, or more often if required.
As the additives (SCA’s) in your coolant that keep it neutralized become depleted the
coolant actually develops an electric charge from passing over dissimilar metals. This
small electric current removes metal from engine surfaces leaving large pits or holes
and can eventually eat entirely through a component. It can also weld bolts and
fittings to the engine and components. A Digital Voltmeter can be used to test the
strength of SCA Package in the Engine Coolant:
1) Set the Digital Voltmeter to read at the lowest DC Voltage Setting.
2) Attach the Digital Voltmeter Negative (-) Probe to the Negative (-) Battery Post.
3) Insert the tip of the Digital Voltmeter Positive (+) Probe into the coolant and
observe the reading.
4) If the Digital Voltmeter registers:
0.10 – 0.19 Volts – The engine coolant SCA package is still good.
0.20 – 0.24 Volts – The engine cooling system should be schedule to be
drained and flushed, and have the Antifreeze replaced.
0.25 or greater Volts – The engine cooling system should be drained and
flushed, and have the Antifreeze replaced immediately.
Some Lift Trucks are delivered with a Traditional Ethylene Glycol Antifreeze /
Coolant in the Engine Cooling System. The Traditional Ethylene Glycol used by
CLARK, is a low silicate formulation based (IAT Technology) Antifreeze/Coolant,
usually green in color, that is suitable for light trucks and heavy duty vehicles, and also
protects all engine cooling system metals from corrosion including aluminum. Many
recommend servicing the Engine Coolant / Cooling System as described previously in
this Service Bulletin.
When servicing the engine cooling system many recommend using the Pre-
Charged Heavy Duty 50/50 Premixed Antifreeze (red in color)
which is a gallon container. It is extremely important that the engine
cooling system be flushed with Super Flush and
thoroughly drained before refilling the system with the Pre-Charged Heavy Duty 50/50
premixed Antifreeze. Using the Pre-Charged heavy Duty Antifreeze should
dramatically reduce engine cooling system maintenance.
As a minimum, the Antifreeze/Coolant to be used in Lift Trucks must meet or
exceed the following specifications and /or recommended practices:
ASTM D3306 GM 1899M Cummins 90T8-4
ASTM D4985 GM 1825M TMC of ATA RP-302B
SAE J814c Ford ESE-M97B44-A Federal Specification A-A-870A
SAE J1034 Chrysler MS7170 Clarke – Approved
SAE J1941 Detroit Diesel 7SE298
TYPICAL CHARACTERISTICS OF
TRADITIONAL ETHYLENE GLYCOL ANTIFREEZE / COOLANT:
Appearance Fluorescent Green
Specific Gravity 60/60°F 1.130
Freezing Point (ASTM D1177), 50% Volume, q.s.
pH (ASTM D1287), 1:2 dilution with water 10.5
Reserve Alkalinity (ASTM D1121) as received 12.0
Silicate (as Anhdyrous Alkali Metasilicate) 0.09%