CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only a original equipment clamp
with matching number or letter (Fig. 2).

OPERATION - HOSE CLAMPS

The worm type hose clamp uses a specified torque

value to maintain proper tension on a hose connec-
tion.

The spring type hose clamp applies constant ten-

sion on a hose connection. To remove a spring type
hose clamp, use Special Tool 6094 or equivalent, con-
stant tension clamp pliers (Fig. 3) to compress the
hose clamp.

DIAGNOSIS AND TESTING

ON-BOARD DIAGNOSTICS - OBD

COOLING SYSTEM RELATED DIAGNOSTICS

The Powertrain Control Module (PCM) has been

programmed to monitor the certain following cooling
system components:

• If the engine has remained cool for too long a

period, such as with a stuck open thermostat, a Diag-
nostic Trouble Code (DTC) can be set.

• If an open or shorted condition has developed in

the relay circuit controlling the electric radiator fan,
a Diagnostic Trouble Code (DTC) can be set.

If the problem is sensed in a monitored circuit

often enough to indicate an actual problem, a DTC is
stored. The DTC will be stored in the PCM memory
for eventual display to the service technician.

ACCESSING DIAGNOSTIC TROUBLE CODES

To read DTC’s and to obtain cooling system data,

(Refer to 25 - EMISSIONS CONTROL - DESCRIPTION).

DIAGNOSIS AND TESTING - PRELIMINARY
CHECKS

ENGINE COOLING SYSTEM OVERHEATING

Establish what driving conditions caused the com-

plaint. Abnormal loads on the cooling system such as
the following may be the cause:

• Prolonged idle

• Very high ambient temperature

• Slight tail wind at idle

• Slow traffic

• Traffic jams

• High speed or steep grades
Driving techniques that avoid overheating are:

Fig. 2 Spring Clamp Size Location

1 - SPRING CLAMP SIZE LOCATION

Fig. 3 Hose Clamp Tool

1 - HOSE CLAMP TOOL 6094
2 - HOSE CLAMP

7 - 2

COOLING

COOLING (Continued)

• Idle with A/C off when temperature gauge is at

end of normal range.

• Increasing engine speed for more air flow is rec-

ommended.

TRAILER TOWING:

Consult Trailer Towing section of owners manual.

Do not exceed limits.

AIR CONDITIONING; ADD-ON OR AFTER MARKET:

A maximum cooling package should have been

ordered with vehicle if add-on or after market A/C is
installed. If not, maximum cooling system compo-
nents should be installed for model involved per
manufacturer’s specifications.

RECENT SERVICE OR ACCIDENT REPAIR:

Determine if any recent service has been per-

formed on vehicle that may effect cooling system.
This may be:

• Engine adjustments (incorrect timing)

• Slipping engine accessory drive belt(s)

• Brakes (possibly dragging)

• Changed parts. Incorrect water pump or pump

rotating in wrong direction due to belt not correctly
routed

• Reconditioned radiator or cooling system refill-

ing (possibly under filled or air trapped in system).

NOTE: If investigation reveals none of the previous
items as a cause for an engine overheating com-
plaint,

refer

COOLING

SYSTEM

DIAGNOSIS

CHART BELOW.

These charts are to be used as a quick-reference

only. Refer to COOLING SYSTEM DIAGNOSIS
CHART

COOLING SYSTEM DIAGNOSIS CHART

CONDITION

POSSIBLE CAUSES

CORRECTION

TEMPERATURE GAUGE READS
LOW

1. Has a Diagnostic Trouble Code
(DTC) been set indicating a stuck
open thermostat?

1. (Refer to 25 - EMISSIONS
CONTROL - DESCRIPTION) for
On-Board Diagnostics and DTC
information. Replace thermostat if
necessary.

2. Is the temperature sending unit
connected?

2. Check the temperature sensor
connector. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER -
SCHEMATIC - ELECTRICAL) Repair
connector if necessary.

3. Is the temperature gauge operating
OK?

3. Check gauge operation. (Refer to 8
- ELECTRICAL/INSTRUMENT
CLUSTER/ENGINE TEMPERATURE
GAUGE - DESCRIPTION). Repair as
necessary.

4. Coolant level low in cold ambient
temperatures accompanied with poor
heater performance.

4. Check coolant level in the coolant
reserve/overflow tank or degas bottle
and the radiator. Inspect system for
leaks. Repair leaks as necessary.
Refer to the Coolant section of the
manual text for WARNINGS and
CAUTIONS associated with removing
the radiator cap.

5. Improper operation of internal
heater doors or heater controls.

5. Inspect heater and repair as
necessary. (Refer to 24 - HEATING &
AIR CONDITIONING - DIAGNOSIS
AND TESTING) for procedures.

COOLING

7 - 3

COOLING (Continued)

CONDITION

POSSIBLE CAUSES

CORRECTION

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 or degas bottle. If neck is bent
or damaged, replace radiator or
degas bottle.

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

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).

7 - 4

COOLING

COOLING (Continued)

Content .. 258 259 260 261 ..