Dodge RAM TRUCK 1500 1995 Service Manual page 310

7 - 40 COOLING SYSTEM SERVICE PROCEDURES
B R
TESTING COOLING SYSTEM FOR LEAKS
ULTRAVIOLET LIGHT METHOD
A leak detection additive is available through the
parts department that can be added to cooling sys­
tem. The additive is highly visible under ultraviolet
light (black light). Pour one ounce of additive into
cooling system. Place heater control unit in HEAT
position. Start and operate engine until radiator up­
per hose is warm to touch. Aim the commercially
available black light tool at components to be
checked. If leaks are present, black light will cause
additive to glow a bright green color.
The black light can be used in conjunction with a
pressure tester to determine if any external leaks ex­
ist (Fig. 56).
Fig. 56 Leak Detection Using Black Light—Typical
PRESSURE TESTER METHOD
The engine should be at normal operating temper­
ature. Recheck the system cold if cause of coolant
loss is not located during the warm engine examina­
tion.
WARNING: HOT, P R E S S U R I Z E D COOLANT CAN
C A U S E I N J U R Y B Y SCALDING.
Carefully remove radiator pressure cap from filler
neck and check coolant level. Push down on cap to
disengage it from stop tabs. Wipe inside of filler neck
and examine lower inside sealing seat for nicks,
cracks, paint, dirt and solder residue. Inspect radia­
tor-to-reserve/overflow tank hose for internal obstruc­
tions. Insert a wire through the hose to be sure it is
not obstructed.
Inspect cams on outside of filler neck. If cams are
bent, seating of pressure cap valve and tester seal
will be affected. Replace cap if cams are bent.
Attach pressure tester (7700 or an equivalent) to
radiator filler neck (Fig. 57).
Fig. 57 Pressure Testing Cooling System—Typical
Operate tester pump to apply 103.4 kPa (15 psi)
pressure to system. If hoses enlarge excessively or
bulges while testing, replace as necessary. Observe
gauge pointer and determine condition of cooling sys­
tem according to following criteria:
Holds Steady: If pointer remains steady for two
minutes, serious coolant leaks are not present in sys­
tem. However, there could be an internal leak that
does not appear with normal system test pressure. If
it is certain that coolant is being lost and leaks can­
not be detected, inspect for interior leakage or per­
form Internal Leakage Test.
' Drops Slowly: Indicates a small leak or seepage is
occurring. Examine all connections for seepage or
slight leakage with a flashlight. Inspect radiator,
hoses, gasket edges and heater. Seal small leak holes
with a sealer lubricant (or equivalent). Repair leak
holes and inspect system again with pressure ap­
plied.
Drops Quickly: Indicates that serious leakage is
occurring. Examine system for external leakage. If
leaks are not visible, inspect for internal leakage.
Large radiator leak holes should be repaired by a
reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove engine oil pan drain plug and drain a
small amount of engine oil. If coolant is present in
the pan, it will drain first because it is heavier than
oil. An alternative method is to operate engine for a
short period to churn the oil. After this is done, re­
move engine dipstick and inspect for water globules.
Also inspect transmission dipstick for water globules
and transmission fluid cooler for leakage.