Chrysler RAM TRUCK 2500 1994 Service Manual page 290

COOLING SYSTEM 7 - 35
100% Ethylene-Glycol-The corrosion inhibiting
additives i n ethylene-glycol need the presence of wa­
ter to dissolve. Without water, additives form depos­
its in system. These act as insulation causing
temperature to rise to as high as 149°C (300°F). This
temperature is hot enough to melt plastic and soften
solder. The increased temperature can result i n en­
gine detonation. I n addition, 100 percent ethylene-
glycol freezes at -22°C (-8°F).
50/50 Ethylene-Glycol and Water-Is the recom­
mended mixture, i t provides protection against freez­
ing to -37°C (-35°F). The antifreeze concentration
must always be a minimum of 44 percent, year-
round in all climates. I f percentage is lower, engine
parts may be eroded by cavitation. Maximum protec­
tion against freezing is provided with a 68 percent
antifreeze concentration, which prevents freezing
down to -67.7°C (-90°F). A higher percentage will
freeze at a warmer temperature. Also, a higher per­
centage of antifreeze can cause the engine to over­
heat because specific heat of antifreeze is lower than
that of water.
CAUTION: Richer antifreeze mixtures cannot be
measured with normal field equipment and can
c a u s e problems associated with 100 percent ethyl­
ene-glycol.
COOLANT SELECTION^ADDITIVES
The presence of aluminum components i n the cool­
ing system requires strict corrosion protection. Main­
tain coolant at specified level with a mixture of
ethylene-glycol based antifreeze and water. Only use
an antifreeze containing ALUGARD 340-2 ™ such as
Mopar Antifreeze. I f coolant becomes contaminated
or looses color, drain and flush cooling system and fill
with correctly mixed solution.
CAUTION: Do not u s e coolant additives that are
claimed to improve engine cooling.
COOLANT SERVICE—EXCEPT DIESEL
It is recommended that the cooling system be
drained and flushed at 84,000 kilometers (52,500
miles) or 3 years, whichever occurs first. Then every
two years or 48,000 kilometers (30,000 miles), which­
ever occurs first.
COOLANT SERVICE—DIESEL ENGINE
I t is recommended that the cooling system be
drained and flushed every 24 months or 38,600 kilo­
meters (24,000 miles), whichever occurs first.
COOLANT LEVEL CHECK—ROUTINE
D o not remove radiator cap for routine cool­
ant level inspections. The coolant level can be
checked at the coolant reserve/overflow tank.
The coolant reserve/overflow system provides a
quick visual method for determining the coolant level
without removing the radiator pressure cap. With en­
gine idling and at normal operating temperature, ob­
serve coolant level i n coolant reserve/overflow tank.
The coolant level should be between the ADD and
FULL marks.
ADDING ADDITIONAL COOLANT—ROUTINE
Do not remove the radiator cap to add cool­
ant to the system. When adding coolant to main­
tain the correct level, do so at the coolant reserve/
overflow tank with a 50/50 mixture of ethylene-glycol
antifreeze (containing Alugard 340-2 ™) and water.
Remove the radiator cap only for testing or when re­
filling the system after service. Removing cap unnec­
essarily can cause loss of coolant and allow air to
enter system. This produces corrosion.
COOLANT LEVEL CHECK—SERVICE
The cooling system is closed and designed to main­
tain coolant level to the top of the radiator.
WARNING: DO NOT OPEN RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING SYSTEM IS UNDER PRESSURE.
When vehicle servicing requires a coolant level
check i n the radiator, drain several ounces of coolant
from the radiator drain cock. Do this while observing
the coolant reserve/overflow system tank. The coolant
level i n the reserve/overflow tank should drop
slightly. I f not, inspect for a leak between radiator
and coolant reserve/overflow system connection. Re­
move radiator cap. The coolant level should be to the
top of the radiator. I f not and i f coolant level i n re­
serve/overflow tank is at the ADD mark, check for:
• A n air leak i n the coolant reserve/overflow tank
• A n air leak i n the radiator filler neck
• Leak i n the pressure cap seal to the radiator filler
neck
LOW COOLANT LEVEL-AERATION
I f the coolant level i n the radiator drops below the
top of the radiator core tubes, air will enter the sys­
tem.
Low coolant level can cause the thermostat pellet
to be suspended i n air instead of coolant. This will
cause the thermostat to open later, which in turn
causes higher coolant temperature. A i r trapped i n
cooling system also reduces the amount of coolant
circulating i n the heater core. This may result i n low
heat output.
DEAERATION
As the engine operates, air trapped i n the cooling
system gathers under the radiator cap. The next time
engine is operated, thermal expansion of coolant will