Dodge ram truck 3500 1996 Service Manual page 301

B R — — — COOLING SYSTEM 7 - 1 7
D I A G N O S I S A N D T E S T I N G (Continued)
COOLING SYSTEM DIAGNOSIS—ALL EXCEPT DIESEL—CONTINUED
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.
2. Temperature gauge or engine
mounted gauge sensor defective
or shorted. Also, corroded or
loose wiring in this circuit.
3. Gauge reading rises when vehicle
is brought to a stop after heavy
use (engine still running).
4. Gauge reading high after re­
starting a warmed-up (hot)
engine.
5. Coolant level low in radiator (air
will build up in the cooling system
causing the thermostat to open
late).
6. Cylinder head gasket leaking
allowing exhaust gas to enter
cooling system causing
thermostat to open late.
7. Water pump impeller loose on
shaft.
8. Loose accessory drive belt (water
pump slipping).
9. Air leak on the suction side of
water pump allows air to build up
in cooling system causing
thermostat to open late.
1. A normal condition. No correction is
necessary.
2. Check operation of gauge and repair if
necessary. Refer to Group 8E, Instrument
Panel And Gauges.
3. A normal condition. No correction is
necessary. Gauge reading should return to
normal range after vehicle is driven.
4. A normal condition. No correction is
necessary. The gauge should return to
normal range after a few minutes of engine
operation.
5. Check and correct coolant leaks. Refer to
Testing Cooling System For Leaks in this
group.
6. (a) Check for cylinder head gasket leaks
with a commercially available Block
Leak Tester. Repair as necessary.
(b) Check for coolant in the engine oil.
Inspect for white steam emitting from
exhaust system. Repair as necessary.
7. Check water pump and replace as
necessary. Refer to Water Pumps in this
group.
8. Refer to Engine Accessory Drive Belts in
this group. Check and correct as
necessary.
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 IS 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 Testing Cooling System For
Leaks in this group.
J9507-51