Dodge Ram Truck 1500-2500-3500. Manual - part 227

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. 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).

7 - 14

COOLING

DR/DH

CONDITION

POSSIBLE CAUSES

CORRECTION

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.

DR/DH

COOLING

7 - 15

CONDITION

POSSIBLE CAUSES

CORRECTION

Temperature gauge reading is
inconsistent (fluctuates, cycles or is
erratic)

1. During cold weather operation,
with the heater blower in the high
position, the gauge reading may
drop slightly.

1. A normal condition. No correction
necessary.

2. Temperature gauge or engine
mounted gauge sensor defective or
shorted. Also, corroded or loose
wiring in this circuit.

2. Check operation of gauge and
repair if necessary. (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING).

3. Gauge reading rises when
vehicle is brought to a stop after
heavy use (engine still running)

3. A normal condition. No correction
is necessary. Gauge should return
to normal range after vehicle is
driven.

4. Gauge reading high after
re-starting a warmed up (hot)
engine.

4. A normal condition. No correction
is necessary. The gauge should
return to normal range after a few
minutes of engine operation.

5. Coolant level low in radiator (air
will build up in the cooling system
causing the thermostat to open
late).

5. Check and correct coolant leaks.
(Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).

6. Cylinder head gasket leaking
allowing exhaust gas to enter
cooling system causing a
thermostat to open late.

6. (a) Check for cylinder head
gasket leaks. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING).

(b) Check for coolant in the engine
oil. Inspect for white steam emitting
from the exhaust system. Repair as
necessary.

7. Water pump impeller loose on
shaft.

7. Check water pump and replace
as necessary. (Refer to 7 -
COOLING/ENGINE/WATER PUMP -
REMOVAL).

8. Loose accessory drive belt.
(water pump slipping)

8. (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS
- DIAGNOSIS AND TESTING).
Check and correct as necessary.

9. Air leak on the suction side of the
water pump allows air to build up in
cooling system causing thermostat
to open late.

9. Locate leak and repair as
necessary.

PRESSURE CAP IS BLOWING
OFF STEAM AND/OR COOLANT
TO COOLANT TANK.
TEMPERATURE GAUGE READING
MAY BE ABOVE NORMAL BUT
NOT HIGH. COOLANT LEVEL MAY
BE HIGH IN COOLANT RESERVE/
OVERFLOW TANK

1. Pressure relief valve in radiator
cap is defective.

1. Check condition of radiator cap
and cap seals. (Refer to 7 -
COOLING/ENGINE/RADIATOR
PRESSURE CAP - DIAGNOSIS
AND TESTING). Replace cap as
necessary.

7 - 16

COOLING

DR/DH

CONDITION

POSSIBLE CAUSES

CORRECTION

COOLANT LOSS TO THE
GROUND WITHOUT PRESSURE
CAP BLOWOFF. GAUGE READING
HIGH OR HOT

1. Coolant leaks in radiator, cooling
system hoses, water pump or
engine.

1. Pressure test and repair as
necessary. (Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).

DETONATION OR PRE-IGNITION
(NOT CAUSED BY IGNITION
SYSTEM). GAUGE MAY OR MAY
NOT BE READING HIGH

1. Engine overheating.

1. Check reason for overheating
and repair as necessary.

2. Freeze point of coolant not
correct. Mixture is too rich or too
lean.

2. Check coolant concentration.
(Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES -
DESCRIPTION).

HOSE OR HOSES COLLAPSE
WHILE ENGINE IS RUNNING

1. Vacuum created in cooling
system on engine cool-down is not
being relieved through coolant
reserve/overflow system.

1. (a) Radiator cap relief valve
stuck. (Refer to 7 - COOLING/
ENGINE/RADIATOR PRESSURE
CAP - DIAGNOSIS AND TESTING).
Replace if necessary

(b) Hose between coolant
reserve/overflow tank and radiator is
kinked. Repair as necessary.

(d) Reserve/overflow tank is
internally blocked or plugged. Check
for blockage and repair as
necessary.

NOISY VISCOUS FAN/DRIVE

1. Fan blades loose.

1. Replace fan blade assembly.
(Refer to 7 - COOLING/ENGINE/
RADIATOR FAN - REMOVAL)

2. Fan blades striking a surrounding
object.

2. Locate point of fan blade contact
and repair as necessary.

3. Air obstructions at radiator or air
conditioning condenser.

3. Remove obstructions and/or
clean debris or insects from radiator
or A/C condenser.

4. Thermal viscous fan drive has
defective bearing.

4. Replace fan drive. Bearing is not
serviceable. (Refer to 7 - COOLING/
ENGINE/FAN DRIVE VISCOUS
CLUTCH - REMOVAL).

5. A certain amount of fan noise
may be evident on models
equipped with a thermal viscous fan
drive. Some of this noise is normal.

5. (Refer to 7 - COOLING/ENGINE/
FAN DRIVE VISCOUS CLUTCH -
DESCRIPTION) for an explanation
of normal fan noise.

DR/DH

COOLING

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