Dodge RAM TRUCK 1500 1995 Service Manual page 308

7 - 38 COOLING SYSTEM SERVICE PROCEDURES
H R
serve coolant level in 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 a d d 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 O P E N RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING S Y S T E M IS UNDER P R E S S U R E .
When vehicle servicing requires a coolant level
check in 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 in the reserve/overflow tank should drop
slightly. If 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. If not and if coolant level in re­
serve/overflow tank is at the ADD mark, check for:
o An air leak in the coolant reserve/overflow tank
® An air leak in the radiator filler neck
• Leak in the pressure cap seal to the radiator filler
neck
LOW COOLANT LEVEL-AERATION
If the coolant level in 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 in air instead of coolant. This will
cause the thermostat to open later, which in turn
causes higher coolant temperature. Air trapped in
cooling system also reduces the amount of coolant
circulating in the heater core. This may result in low
heat output.
DEAERATION
As the engine operates, air trapped in the cooling
system gathers under the radiator cap. The next time
engine is operated, thermal expansion of coolant will
push trapped air past radiator cap into coolant re­
serve/overflow tank. Here it escapes to atmosphere in
the tank. When engine cools down the coolant, it will
be drawn from reserve/overflow tank into radiator to
replace removed air.
DRAINING COOLING SYSTEM
WARNING: DO NOT REMOVE THE CYLINDER
B L O C K DRAIN PLUGS OR L O O S E N THE RADIATOR
DRAIN P L U G WITH S Y S T E M HOT AND UNDER
P R E S S U R E . S E R I O U S B U R N S FROM COOLANT
CAN OCCUR.
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
(1) Start the engine and place the heater control
temperature selector in the Full-On position. Engine
vacuum is needed to actuate the heater controls.
(2) Turn the ignition off.
(3) Do not remove radiator cap when draining cool­
ant from reserve/overflow tank. Open radiator drain
plug and when tank is empty, remove radiator cap. If
the coolant reserve/overflow tank does not drain, re­
fer to the Testing Cooling System for Leaks section in
this group. The coolant need not be removed from
tank unless the system is being refilled with fresh
mixture.
(4) On vehicles equipped with gas powered en­
gines, remove the cylinder block drain plugs. These
are located on the sides of the block just above the oil
pan (Fig. 54).
Fig. 54 Drain Plugs—Gas Powered Engines—Typical
(5) Remove radiator pressure cap.
REFILLING COOLING SYSTEM
Clean cooling system prior to refilling. Refer to
Cooling' System Cleaning section of this group.
(1) Install the cylinder block drain plugs (Fig. 54).
(2) Close radiator drain plug.
(3) Fill the cooling system with a 50/50 mixture of
water and antifreeze. 5.9L Diesel Engine Only: The