Dodge RAM TRUCK 1500 1995 Service Manual page 311

COOLING SYSTEM SERVICE PROCEDURES 7 - 41
WARNING: WITH COOLING S Y S T E M P R E S S U R E
TESTER TOOL INSTALLED ON RADIATOR, DO NOT
A L L O W P R E S S U R E TO E X C E E D 110 KPA (20 PSI).
P R E S S U R E W I L L BUILD UP QUICKLY IF A COM­
BUSTION LEAK IS P R E S E N T TO RELEASE PRES­
S U R E , ROCK T E S T E R FROM SIDE TO SIDE. W H E N
REMOVING T E S T E R , DO NOT TURN T E S T E R MORE
THAN 1/2 TURN IF SYSTEM IS UNDER P R E S S U R E .
Operate engine without pressure cap on radiator
until thermostat opens. Attach a pressure tester to
filler neck. If pressure builds up quickly it indicates a
combustion leak exists. This is usually the result of a
cylinder head gasket leak or crack in engine. Repair
as necessary.
If there is not an immediate pressure increase,
pump the pressure tester. Do this until indicated
pressure is within system range of 110 kPa (16 psi).
Fluctuation of gauge pointer indicates compression or
combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic
converter, do not remove spark plug cables or short
out cylinders (non-diesel engines) to isolate compres­
sion leak.
If the needle on dial of pressure tester does not
fluctuate, race engine a few times to check for an ab­
normal amount of coolant or steam. This would be
emitting from exhaust pipe. Coolant or steam from
exhaust pipe may indicate a faulty cylinder head gas­
ket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail­
able Block Leak Check tool. Follow manufacturers in­
structions when using this product.
COMBUSTION LEAKAGE TEST—WITHOUT
PRESSURE TESTER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE CYLINDER B L O C K
DRAIN P L U G S OR L O O S E N RADIATOR DRAIN-
COCK WITH S Y S T E M HOT A N D 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.
Drain sufficient coolant to allow thermostat re­
moval. Refer to Thermostat Replacement. Disconnect
water pump drive belt.
Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of top of thermostat housing.
CAUTION: Avoid overheating. Do not operate en­
gine for an excessive period of time. Open drain-
cock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to
approximately 3000 rpm (2000 rpm for diesel) while
observing coolant. If internal engine combustion
gases are leaking into cooling system, bubbles will
appear in coolant. If bubbles do not appear, internal
combustion gas leakage is not present.
COOLANT RESERVE/OVERFLOW SYSTEM
The coolant reserve/overflow system works in con­
junction with the radiator pressure cap. It utilizes
thermal expansion and contraction of coolant to keep
coolant free of trapped air. It provides a volume for
expansion and contraction of coolant. It also provides
a convenient and safe method for checking coolant
level and adjusting level at atmospheric pressure.
This is done without removing the radiator pressure
cap. The system also provides some reserve coolant
to the radiator to cover minor leaks and evaporation
or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool­
ant will then be drawn from the coolant tank and re­
turned to a proper level in the radiator.
On 3.9L/5.2L/5.9L gas engines and the 5.9L diesel
engine, the coolant reserve/overflow tank is mounted
to the side of the fan shroud (Fig. 58). On the 8.0L
V-10 engine the tank is mounted to right inner
fender (Fig. 59).
Fig. 58 Coolant Reserve/Overflow Tank—All Except
8.0L V-10 Engine
Refer to Coolant Level Check—Service, Deaeration
and Radiator Pressure Cap sections in this group for
coolant reserve/overflow system operation and ser­
vice.
Should the reserve/overflow tank become coated
with corrosion, it can be cleaned with detergent and