Dodge RAM TRUCK 1500 1995 Service Manual page 271

BR
COOLING SYSTEM 7 - 1
COOLING SYSTEM
C O N T E N T S
page
AUTOMATIC TRANSMISSION OIL COOLERS .. 50
DIAGNOSIS 4
ENGINE ACCESSORY DRIVE BELTS 54
GENERAL INFORMATION
Throughout this group, references are made to par­
ticular vehicle models by alphabetical designation or
by the particular vehicle nameplate. A chart showing
a breakdown of alphabetical designations is included
in the Introduction section at the beginning of this
manual.
All vehicles are equipped with either a 3.9L V-6 en­
gine, a 5.2L V-8 engine, two different 5.9L V-8 en­
gines, an 8.0L V-10 engine or a 5.9L Cummins in-line
6 cylinder diesel engine.
The 3.9L V-6 and 5.2L V-8 engines will be referred
to in this Cooling group as: LDC (Light Duty Cycle)
engines. The 5.9L V-8 gas powered engine will be re­
ferred to as either: LDC (Light Duty Cycle) or HDC
(Heavy Duty Cycle) engine. The 8.0L V-10 engine will
be referred to as: HDC (Heavy Duty Cycle) engine.
Either of the HDC gas powered engines can be eas­
ily identified by the use of an engine mounted air in­
jection pump. The 3.9L V-6, 5.2/5.9L V-8 LDC gas
engines or the diesel engine will not use an air injec­
tion pump.
COOLING SYSTEM
The cooling system regulates engine operating tem­
perature. It allows the engine to reach normal oper­
ating temperature as quickly as possible. It also
maintains normal operating temperature and pre­
vents overheating.
The cooling system also provides a means of heat­
ing the passenger compartment and cooling the auto­
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump on all engines to circulate coolant throughout
the system.
An optional factory installed maximum duty cool­
ing package is available for some engines on most
models. This package will provide additional cooling
capacity for vehicles used under extreme conditions
such as trailer towing in high ambient temperatures.
COOLING SYSTEM COMPONENTS—ALL EXCEPT
DIESEL ENGINE
The cooling system consists of:
• A cross-flow radiator
page
ENGINE BLOCK HEATERS 61
SERVICE PROCEDURES 18
SPECIFICATIONS 63
• Thermal viscous fan drive
• Fan shroud
© Radiator pressure cap
• Thermostat
• Coolant reserve/overflow system
• Transmission oil cooler (automatic transmission)
© Coolant
• Water pump (to circulate coolant)
© Hoses and hose clamps
Typical coolant flow circuits for gas powered , en­
gines are shown in figure 1.
COOLING S f S T E i C01P01E1TS—DIESEL
ENGINE
Coolant flow circuits for the 5.9L diesel engine are
shown in figure 2.
The diesel cooling system consists of: a cross-flow
radiator, engine driven cooling fan, thermal viscous
fan drive, fan shroud, radiator pressure cap, thermo­
stat, a vertically mounted one-way check valve (jiggle
pin) at cylinder head, a bypass hose at thermostat,
coolant reserve/overflow system, transmission oil
cooler (if equipped with an automatic transmission),
coolant, water pump, hoses and hose clamps.
Coolant is drawn from radiator into the water
pump. Water pump output is directed to the engine
oil cooler cavity of the cylinder block (Fig. 3).
From the oil cooler cavity, the coolant circulates
around each cylinder. It then crosses to the transfer
(lift) pump side of the engine where it flows up into
the cylinder head through openings in top of the cyl­
inder block (Fig. 3). Coolant flows past the valve
bridges (Fig. 4), to exhaust manifold side of engine
and to thermostat. As coolant flows toward the ther­
mostat, it provides cooling for the injector nozzle.
Also refer to Thermostat Operation—5.9L Diesel
Engine. This can be found in the Thermostat section
of this group.