To hopefully avoid just throwing parts at issue, should try and go thru checks/diagnostics.
TEMPERATURE GAUGE READS
HIGH OR THE COOLANT
WARNING LAMP ILLUMINATES.
COOLANT MAY OR MAY NOT BE
LOST OR LEAKING FROM THE
COOLING SYSTEM
1. Trailer is being towed, a steep
hill is being climbed, vehicle is
operated in slow moving traffic, or
engine is being idled with very high
ambient (outside) temperatures and
the air conditioning is on. Higher
altitudes could aggravate these
conditions.
1. This may be a temporary
condition and repair is not
necessary. Turn off the air
conditioning and attempt to drive the
vehicle without any of the previous
conditions. Observe the temperature
gauge. The gauge should return to
the normal range. If the gauge does
not return to the normal range,
determine the cause for overheating
and repair. Refer to Possible
Causes (2-18).
2. Is the temperature gauge reading
correctly?
2. Check gauge. (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - SCHEMATIC -
ELECTRICAL). Repair as
necessary.
3. Is the temperature warning
illuminating unnecessarily?
3. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER -
SCHEMATIC - ELECTRICAL).
4. Coolant low in coolant reserve/
overflow tank and radiator?
4. Check for coolant leaks and
repair as necessary. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING).
5. Pressure cap not installed tightly.
If cap is loose, boiling point of
coolant will be lowered. Also refer
to the following Step 6.
5. Tighten cap
6. Poor seals at the radiator cap. 6. (a) Check condition of cap and
cap seals. Refer to Radiator Cap.
Replace cap if necessary.
(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator (5.9L Diesel) or
degas bottle (3.7L, 4.7L).
7. Coolant level low in radiator but
not in coolant reserve/overflow tank.
This means the radiator is not
drawing coolant from the coolant
reserve/overflow tank as the engine
cools (5.9L Diesel).
7. (a) Check condition of radiator
cap and cap seals. Refer to
Radiator Cap in this Group. Replace
cap if necessary.
(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator.
(c) Check condition of the hose from
the radiator to the coolant tank. It
should fit tight at both ends without
any kinks or tears. Replace hose if
necessary.
(d) Check coolant reserve/overflow
tank and tanks hoses for blockage.
Repair as necessary.
8. Incorrect coolant concentration
8. Check coolant. (Refer to
LUBRICATION & MAINTENANCE/
FLUID TYPES - DESCRIPTION).
9. Coolant not flowing through
system
9. Check for coolant flow at radiator
filler neck with some coolant
removed, engine warm and
thermostat open. Coolant should be
observed flowing through radiator. If
flow is not observed, determine area
of obstruction and repair as
necessary.
10. Radiator or A/C condenser fins
are dirty or clogged.
10. Remove insects and debris.
(Refer to 7 - COOLING -
STANDARD PROCEDURE).
11. Radiator core is corroded or
plugged.
11. Have radiator re-cored or
replaced.
12. Fuel or ignition system
problems.
12. Refer to 14 - Fuel System or 8 -
Electrical for diagnosis and testing
procedures.
13. Dragging brakes.
13. Check and correct as necessary.
(Refer to 5 - BRAKES -
DIAGNOSIS AND TESTING) for
correct procedures.
14. Bug screen or cardboard is
being , reducing air flow.
14. Remove bug screen or
cardboard.
15. Thermostat partially or
completely shut.
15. Check thermostat operation and
replace as necessary. (Refer to 7 -
COOLING/ENGINE/ENGINE
COOLANT THERMOSTAT -
REMOVAL) .
16. Viscous fan drive not operating
properly.
16. Check fan drive operation and
replace as necessary. (Refer to 7 -
COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - REMOVAL).
17. Cylinder head gasket leaking.
17. Check for cylinder head gasket
leaks. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
18. Heater core leaking. 18. Check heater core for leaks.
(Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING -
DIAGNOSIS AND TESTING).
Repair as necessary
