Testing Cooling System For Leaks - Dodge ram truck 3500 1996 Service Manual

B R
COOLING SYSTEM 7 - 27
D I A G N O S I S A N D T E S T I N G ( C o n t i n u e d )
RADIATOR COOLANT FLOW TEST
Use the following procedure to determine i f coolant
is flowing through the cooling system,
(1) Idle engine until operating temperature is
reached. I f the upper radiator hose is warm to the
touch, the thermostat is opening and coolant is flow­
ing to the radiator.
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. USING A RAG TO
COVER THE RADIATOR PRESSURE CAP, OPEN
RADIATOR CAP SLOWLY TO THE FIRST STOP. THIS
WILL ALLOW ANY BUILT-UP PRESSURE TO VENT
TO THE RESERVE/OVERFLOW TANK. AFTER PRES­
SURE BUILD-UP HAS BEEN RELEASED, REMOVE
CAP FROM FILLER NECK.
(2) Drain a small amount of coolant from the radi­
ator until the ends of the radiator tubes are visible
through the filler neck. Idle the engine at normal
operating temperature. I f coolant is flowing past the
exposed tubes, the coolant is circulating.
TESTING COOLING SYSTEM FOR LEAKS
PRESSURE TESTER METHOD
The engine should be at normal operating temper­
ature. Recheck the system cold i f cause of coolant
loss is not located during the warm engine examina­
tion.
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY 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
obstructions. Insert a wire through the hose to be
sure i t is not obstructed.
Inspect cams on outside of filler neck. I f cams are
bent, seating of pressure cap valve and tester seal
will be affected. Replace cap i f cams are bent.
Attach pressure tester (7700 or an equivalent) to
radiator filler neck (Fig. 32).
Operate tester pump to apply 103.4 kPa (15 psi)
pressure to system. I f 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: I f pointer remains steady for two
minutes, serious coolant leaks are not present i n sys­
tem. However, there could be an internal leak that
does not appear with normal system test pressure. I f
it is certain that coolant is being lost and leaks can-
Fig. 32 Pressure Testing Cooling System—Typical
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
applied.
Drops Quickly: Indicates that serious leakage is
occurring. Examine system for external leakage. I f
leaks are not visible, inspect for internal leakage.
Large radiator leak holes should be repaired by a
reputable radiator repair shop.
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 i n HEAT
position. Start and operate engine until radiator
upper hose is warm to touch. Aim the commercially
available black light tool at components to be
checked. I f 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 i f any external leaks
exist (Fig. 33).
INTERNAL LEAKAGE TEST
Remove engine oil pan drain plug and drain a
small amount of engine oil. I f 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,
remove engine dipstick and inspect for water glob­
ules. Also inspect transmission dipstick for water
globules and transmission fluid cooler for leakage.