Chrysler RAM TRUCK 2500 1994 Service Manual page 291

7 - 36 COOLING SYSTEM
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push trapped air past radiator cap into coolant re­
serve/overflow tank. Here i t escapes to atmosphere i n
the tank. When engine cools down the coolant, i t will
be drawn from reserve/overflow tank into radiator to
replace removed air.
DRAINING COOLING SYSTEM
WARNING: DO NOT R E M O V E T H E C Y L I N D E R
B L O C K DRAIN P L U G S OR L O O S E N T H E 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 C O O L A N T
CAN O C C U R .
DO NOT WASTE reusable coolant. I f the solution
is clean, drain the coolant into a clean container for
reuse.
(1) Start the engine and place the heater control
temperature selector i n 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. I f
the coolant reserve/overflow tank does not drain, re­
fer to the Testing Cooling System for Leaks section i n
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. 55).
Fig. 55 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. 55).
(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
diesel engine is equipped with a one-way check valve
(jiggle pin). The check valve is used as a servicing
feature and will vent air when the system is being
filled. Water pressure (or flow) will hold the valve
closed. Due to the use of t h i s valve, the engine
must not be operating when refilling the cool­
ing system. Refer to Thermostat Operation—5.9L
Diesel Engine i n the Thermostat section of this group
for more information.
(4) Fill coolant reserve/overflow tank to the FULL
mark.
(5) Start and operate engine until thermostat
opens. Upper radiator hose should be warm to touch.
(6) I f necessary, add 50/50 water and antifreeze
mixture to the coolant reserve/overflow tank to main­
tain coolant level. This level should be between the
ADD and FULL marks. The level i n the reserve/over­
flow tank may drop below the ADD mark after three
or four warm-up and cool-down cycles.
COOLING SYSTEM CLEANING/REVERSE FLUSHING
CLEANING
Drain cooling system and refill with water. Run en­
gine with radiator cap installed until upper radiator
hose is hot. Stop engine and drain water from sys­
tem. I f water is dirty, fill system with water, run en­
gine and drain system. Repeat until water drains
clean.
REVERSE FLUSHING
Reverse flushing of cooling system is the forcing of
water through the cooling system. This is done using
air pressure i n the opposite direction of normal cool­
ant flow. I t is usually only necessary with very dirty
systems with evidence of partial plugging.
R E V E R S E FLUSHING RADIATOR
Disconnect radiator hoses from radiator inlet and
outlet. Attach a section of radiator hose to radiator
bottom outlet fitting and insert flushing gun. Con­
nect a water supply hose and air supply hose to
flushing gun.
CAUTION: Internal radiator pressure must not ex­
ceed 138 k P a (20 psi) a s damage to radiator may re­
sult.
Allow radiator to fill with water. When radiator is
filled, apply air i n short blasts. Allow radiator to re­
fill between blasts. Continue this reverse flushing
until clean water flows out through rear of radiator
cooling tube passages. Have radiator cleaned more
extensively by a radiator repair shop.