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 is
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 Group 8E,
Instrument Panel and Gauges.
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 Cooling System-Testing for
leaks in this group.
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 Cooling System-Testing
for Leaks in this group.
(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 water Pumps in this
group.
8. Loose accessory drive belt. (water
pump slipping)
8. Refer to Accessory Drive Belts in this
group. 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 Radiator Caps in this
group. Replace cap as necessary.
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 Cooling System-
Testing For Leaks in this group.
DN COOLING SYSTEM 7 - 13
DIAGNOSIS AND TESTING (Continued)
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