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COOLING SYSTEM
7 - 3
DIAGNOSIS
INDEX
Preliminary Diagnosis
Page
. . . 3
Symptom and Action
Page
. . . 3
PRELIMINARY DIAGNOSIS
ENGINE COOLING SYSTEM
OVERHEAT
DIAGNOSIS
Establish w h a t " d r i v i n g " conditions caused t h e
complaint. A n y o f t h e following abnormal loads o n
the cooling system m a y be t h e cause.
1. P R O L O N G E D I D L E , V E R Y H I G H
A M B I -
E N T T E M P E R A T U R E , S L I G H T T A I L W I N D A T
I D L E , S L O W T R A F F I C , T R A F F I C J A M S , H I G H
S P E E D , S T E E P
G R A D E S :
D r i v i n g techniques t h a t avoid overheating are:
(a) Idle w i t h A/C off w h e n temperature gauge
is a t end of n o r m a l range.
(b) Increase engine speed for more a i r flow.
2. T R A I L E R
T O W I N G :
Consult t h e " T r a i l e r T o w i n g " section o f the owners
m a n u a l . Do not exceed l i m i t s .
Symptom
3. A I R C O N D I T I O N I N G ;
A D D - O N O R A F T E R
M A R K E T :
A m a x i m u m cooling package should have been or-
dered w i t h t h e vehicle i f add-on or after m a r k e t A/C
is i n s t a l l e d . I f not, m a x i m u m cooling system compo-
nents should be i n s t a l l e d for t h e model involved ac-
cording t o manufacturer's specifications.
4. R E C E N T
S E R V I C E
O R A C C I D E N T R E -
P A I R :
D e te r mi ne i f any recent service has been performed
on t h e vehicle t h a t may affect t h e cooling system
such as: engine adjustments (incorrect t i m i n g ) , slip-
p i n g accessory drive belt(s), brakes (possibly drag-
ging),
changed
parts
(possibly
wrong),
recored
radiator or cooling system r e f i l l i n g (possibly under
filled or trapped a i r ) .
I f i n v e s t i g a t i o n reveals none of t h e above as a
cause for engine overheating complaint refer t o t h e
following symptom a n d action chart.
SYMPTOM and ACTION
(See P r e l i m i n a r y FIRST)
Action
Blinking Engine Temperature
Warning Light Or High Gauge
Indication-Without Coolant
Loss
Coolant Loss
Hot Vehicle (Not Engine)
Heat Damage, Hot Carpet,
Seat, Hot Catalytic
Converter, Smoke,
Burnt Odor
Hot Engine
Crackling Noise
Hot Smell
Severe Local Hot Spots
Coolant Color
Coolant Reserve Bottle
Level Changes
Coolant Not Returning
To Radiator
Normal during temporary operation with heavy load, towing a trailer, high outdoor temperatures,
and/or on~a steep grade.
Improper refilling procedures can result in trapped air in the system. Subsequent operation of the
pressure cap and coolant reserve system will deaereate the cooling system. A low coolant level
will then result in the Coolant Reserve Tank. Add coolant. If condition persists refer to System
Diagnosis.
Check heat shielding, exhaust system, engine emission controls, ignition timing, engine misfiring.
A moderate amount of sound from heating metal can be expected with any vehicle. However, a
crackling sound from the thermostat housing, a hot smell and/or severe local hot spots on an
engine can indicate blocked coolant passages, bad casting, core sand deposits and subsequent
blockage, cracked cylinder block or head, or blown cylinder head gasket. Usually accompanied
with coolant loss.
Coolant color is not necessarily an indication of adequate temperature or corrosion protection.
Level changes are to be expected as coolant volume fluctuates with engine temperature. If the
level in the bottle is between the Maximum and Minimum marks at normal engine operating tem-
perature, the level should return to within that range after operation at elevated temperatures.
Coolant will not return to the radiator if the radiator cap vent valve does not function, if an air leak
destroys vacuum, or if the overflow passage is blocked or restricted. Inspect all portions of the
overflow passage, pressure cap, filler neck nipple, hose, and passages within the bottle for vac-
uum leak only. Coolant return failure will be evident by a low level in the radiator. Reserve bottle
level should increase during heat-up.
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