Coolant—Adding Additional - Dodge 2000 DURANGO Service Manual

DN
SERVICE PROCEDURES (Continued)
higher percentage will freeze at a warmer tempera-
ture. Also, a higher percentage of antifreeze can
cause the engine to overheat because the specific
heat of antifreeze is lower than that of water.
Use of 100 percent ethylene-glycol will cause for-
mation of additive deposits in the system, as the cor-
rosion inhibitive additives in ethylene-glycol require
the presence of water to dissolve. The deposits act as
insulation, causing temperatures to rise to as high as
149 deg. C (300) deg. F). This temperature is hot
enough to melt plastic and soften solder. The
increased temperature can result in engine detona-
tion. In addition, 100 percent ethylene-glycol freezes
at 22 deg. C (-8 deg. F ).
PROPYLENE-GLYCOL MIXTURES
It's overall effective temperature range is smaller
than that of ethylene-glycol. The freeze point of 50/50
propylene-glycol and water is -32 deg. C (-26 deg. F).
5 deg. C higher than ethylene-glycol's freeze point.
The boiling point (protection against summer boil-
over) of propylene-glycol is 125 deg. C (257 deg. F )
at 96.5 kPa (14 psi), compared to 128 deg. C (263
deg. F) for ethylene-glycol. Use of propylene-glycol
can result in boil-over or freeze-up on a cooling sys-
tem designed for ethylene-glycol. Propylene glycol
also has poorer heat transfer characteristics than
ethylene glycol. This can increase cylinder head tem-
peratures under certain conditions.
Propylene-glycol/ethylene-glycol
cause the destabilization of various corrosion inhibi-
tors, causing damage to the various cooling system
components. Also, once ethylene-glycol and propy-
lene-glycol based coolants are mixed in the vehicle,
conventional methods of determining freeze point will
not be accurate. Both the refractive index and spe-
cific gravity differ between ethylene glycol and propy-
lene glycol.
OPERATION
ETHYLENE-GLYCOL MIXTURES
Coolant flows through the engine block absorbing
the heat from the engine, then flows to the radiator
where the cooling fins in the radiator transfers the
heat from the coolant to the atmosphere. During cold
weather the ethylene-glycol coolant prevents water
present in the cooling system from freezing within
temperatures indicated by mixture ratio of coolant to
water.
COOLANT SELECTION AND ADDITIVES
The presence of aluminum components in the cool-
ing system requires strict corrosion protection. Main-
tain coolant at specified level with a mixture of
ethylene-glycol based antifreeze and water. Daimler-
Chrysler Corporation recommends Mopar Antifreeze
or equivalent. If coolant becomes contaminated or
looses color, drain and flush cooling system and fill
with correctly mixed solution.
CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
COOLANT—ADDING ADDITIONAL
Do not remove radiator cap to add coolant to
system. When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene glycol antifreeze containing
Alugard 340-2
Remove radiator cap only for testing or when refill-
ing system after service. Removing cap unnecessarily
can cause loss of coolant and allow air to enter sys-
tem, which produces corrosion.
COOLANT LEVEL CHECK
The cooling system is closed and designed to main-
tain coolant level to top of radiator.
WARNING: DO NOT OPEN RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING SYSTEM IS UNDER PRESSURE.
Remove radiator cap. The coolant level should be
to top of radiator. If not, and if coolant level in cool-
Mixtures can
ant recovery bottle is at ADD mark, check for:
• An air leak in coolant reserve/overflow tank or
its hose
• An air leak in radiator filler neck
• Leak in pressure cap seal to radiator filler neck
COOLING SYSTEM—DRAINING AND FILLING
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
DRAINING
NOTE: On the 4.7L engine the thermostat is an inlet
side thermostat. This means that the engine coolant
will not drain when the radiator drain petcock is
opened. It will be necessary to remove the thermo-
stat housing and thermostat to allow the coolant
traped in the engine block to drain.
(1) Remove radiator pressure cap.
(2) Loosen radiator petcock.
COOLING SYSTEM
and low mineral content water.
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