COOLING SYSTEM
CONTENTS page
DIAGNOSIS
... 4
ENGINE
ACCESSORY
DRIVE BELTS
40
ENGINE
BLOCK HEATERS
48
GENERAL
INFORMATION
Throughout this group, references are made to partic
ular 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 man
ual.
5.9L gas powered engines will be' referred to as ei
ther: LDC (Light Duty Cycle) or HDC (Heavy Duty
Cycle).
COOLING
SYSTEM
The cooling system regulates engine operating tem
perature. It allows the engine to reach normal oper-
page
SERVICE
PROCEDURES
15
SPECIFICATIONS
; 49
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 to circulate coolant throughout the system.
An optional factory installed maximum duty cool
ing package is available on most models. This pack age will provide additional cooling capacity for
vehicles used under extreme conditions such as
trailer towing in high ambient temperatures.
NOTE: HEATER
COOLANT FLOW
CIRCUIT
IS
ALWAYS
OPEN
EXCEPT
WHEN
IN MAX. A/C
OR
OFF
MODES
HEATER
INTAKE MANIFOLD
COOLANT FLOW "METERED" FROM REAR
TO
FRONT
AND
BELOW EXHAUST
HEAT
CROSSOVER
SHUT
OFF
VALVE
A/C
ONLY COOLANT FLOW
-
PUMP
TO
CYLINDER BLOCK,
UP
THROUGH CYLINDER HEADS
TO
INTAKE MANIFOLD WATER
BOX TO
RADIATOR-TO PUMP
•BYPASS
THERMOSTAT CLOSED-HIGH FLOW
THERMOSTAT OPEN
- LOW
FLOW
J9207-18
Fig.
1
Cooling
System
Routing—3.9U5.2L Engine—Typical
•
AUTOMATIC
TRANSMISSION—32RH/36RH/37RH/42RH/46RH
21-103
TRANSMISSION DIAGNOSIS
Condition
Possible
Couso
Correction
OVERHEAT
DURING
COMMERCIAL
OPERATION
OR
WHILE
TRAILER
TOWING
(FLUID
DARK
AND
BURNED
WITH
SOME
SLUDGE
FORMATION)
1.
Vehicle not properly equipped for
trailer
towing or
commercial use
2. Vehicle not equipped
with
auxiliary fluid cooler
3.
Extensive idling
time
or operation in heavy
traffic
in hot weather
4. Tow vehicle overloaded (exceeding vehicle tow capacity)
5. Air flow to auxiliary cooler blocked by snow plow,
front
mounted spare
tire,
bug screen, or similar
item
1.
Be sure vehicle is equipped
with
recommended
optional components
(i.e.,
HD
springs,
transmission,
axle, larger CID engine, auxiliary cooler, correct axle ratio, etc.). If vehicle is not so
equipped, it should not be used for severe
service operation
2. Drain fluid, change
filter,
and install auxiliary cooler
3.
Cut down on idling time; shift into
neutral
every
so
often and run engine at 1000 rpm to help
circulate fluid through cooler
4. Be sure vehicle is properly equipped to handle
load;
do not tow
Class
Ill-type loads
with
a
vehicle
that
is only
rated
for
Class
1
or II operation
5.
Remove or reposition
item
causing
air flow
blockage
OVERHEAT
DURING
NORMAL
OPERATION
(FLUID
DISCOLORED,
SMELLS
BURNED)
1.
Low
fluid
level
2. Fluid cooler, lines blocked, or cooler cracked (oil in engine coolant)
3.
Switch valve sticking
4. Clutch pack clearance incorrect (too tight)
5.
Bands
too tight 1. Add
fluid
and check for leaks
2. Flush cooler and lines and replace radiator if
transmission
fluid has
entered
coolant
3.
Remove,
disassemble,
clean valve body
4. Check and correct as required
5. Adjust bands
J9121-450
