Dodge RAM TRUCK 1500 1995 Service Manual page 313

COOLING SYSTEI SERVICE PROCEDURES 7 - 43
WARNING: IF VEHICLE HAS B E E N RUN RECENTLY,
WAIT AT L E A S T 15 MINUTES B E F O R E REMOVING
RADIATOR CAP, WITH A R A G , S Q U E E Z E RADIATOR
U P P E R H O S E TO C H E C K IF S Y S T E M IS UNDER
P R E S S U R E . P L A C E A R A G OVER CAP AND WITH­
OUT PUSHING CAP DOWN, ROTATE IT COUNTER­
C L O C K W I S E TO FIRST STOP. A L L O W FLUID TO
E S C A P E THROUGH THE COOLANT R E S E R V E /
O V E R F L O W HOSE INTO R E S E R V E / O V E R F L O W
TANK. S Q U E E Z E RADIATOR U P P E R HOSE TO DE­
TERMINE W H E N P R E S S U R E HAS B E E N R E ­
L E A S E D . W H E N COOLANT AND STEAM STOP
B E I N G P U S H E D INTO TANK AND S Y S T E M P R E S ­
S U R E D R O P S , R E M O V E RADIATOR CAP COM­
PLETELY.
PRESSURE TESTING SSADIATOR GAPS
Remove cap from radiator. Be sure that sealing
surfaces are clean. Moisten rubber gasket with water
and install cap on pressure tester 7700 or an equiv­
alent (Fig. 61).
J9507-3
Fig. 61 Pressure Testing Radiator Cap—Typical
Tester
Operate tester pump to bring pressure to 104 kPa
(15 psi) on gauge. If pressure cap fails to hold pres­
sure of at least 97 kPa (14 psi) replace cap. Refer to
CAUTION below.
The pressure cap may test properly while posi­
tioned on tool 7700 (or equivalent). It may not hold
pressure or vacuum when installed on radiator. If so,
inspect radiator filler neck and cap's top gasket for
damage. Also inspect for dirt or distortion that may
prevent cap from sealing properly.
CAUTION: Radiator pressure testing tools are very
sensitive to small air leaks, which will not cause
cooling system problems. A pressure cap that does
not have a history of coolant loss should not be re­
placed just because it leaks slowly when tested
with this tool. Add water to tool. Turn tool upside
down and recheck pressure cap to confirm that cap
needs replacement.
INSPECTION
Hold cap at eye level, right side up. The vent valve
(Fig. 61) at bottom of cap should open. If rubber gas­
ket has swollen and prevents vent valve from open­
ing, replace cap.
Hold cap at eye level, upside down. If any light can
be seen between vent valve and rubber gasket, re­
place cap. Do not use a replacement cap that has
a spring to hold vent shut. A replacement cap
must be the type designed for a coolant reserve/over­
flow system with a completely sealed diaphragm
spring and a rubber gasket. This gasket is used to
seal to radiator filler neck top surface. Use of proper
cap will allow coolant return to radiator.
RADIATORS
GENERAL
INFORMATION
The radiator used on all engines (both gas powered
and diesel) are of a cross-flow design with horizontal
tubes through the radiator core and vertical side
tanks.
Aluminum cores with plastic side tanks are used
on all 3.9L V-6 and 5.2/5.9L V-8 engines. Copper-
brass cores are used with the 8.0L V-10 and diesel
engines.
The radiator supplies sufficient heat transfer to
cool the engine and automatic transmission (if
equipped).
RADIATOR COOLANT FLOW CHECK
Use the following procedure to determine if coolant
is flowing through the cooling system.
(1) Idle engine until operating temperature is
reached. If the upper radiator hose is warm to the
touch, the thermostat is opening and coolant is flow­
ing to the radiator.
WARNING: HOT, P R E S S U R I Z E D COOLANT CAN
C A U S E INJURY B Y SCALDING. USING A R A G TO
COVER THE RADIATOR P R E S S U R E CAP, O P E N RA­
DIATOR CAP S L O W L Y TO THE FIRST STOP. THIS
WILL A L L O W ANY BUILT-UP P R E S S U R E TO VENT
TO THE R E S E R V E / O V E R F L O W TANK. AFTER P R E S ­
S U R E BUILD-UP HAS B E E N R E L E A S E D , REMOVE
CAP FROM F I L L E R NECK.