COOLING SYSTEM DIAGNOSIS CONT.
CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS
HIGH OR ENGINE COOLANT
WARNING LAMP ILLUMINATES.
COOLANT MAY OR MAY NOT BE
LOST FROM SYSTEM.7. Coolant level low in radiator but
not in coolant overflow/reserve
tank. This means the radiator is not
drawing coolant from the coolant
overflow/reserve tank as the engine
cools.
As the engine cools, a vacuum is
formed inside the cooling system. If
the radiator cap seals are defective,
or the cooling system has a leak, a
vacuum can not be formed.7. (a) Check condition of radiator
cap and cap seals. Replace cap if
necessary.
(b) Check condition of filler neck. If
neck is damaged, replace filler
neck.
(c) Check condition of hoses from
filler neck to coolant tank. It should
be tight at both ends without any
kinks or tears. Replace hose if
necessary.
(d) Check coolant overflow/reserve
tank and tank hoses for blockage.
Repair as necessary.
8. Freeze point of coolant not
correct. Mixture may be to rich.8. Check coolant. Refer to coolant
section in this group. Adjust glycol
to water ratio as required.
9. Coolant not flowing through
system.9. Check for coolant flow at filler
neck with some coolant removed,
engine warm and thermostat open.
Coolant should be observed flowing
through filler neck. If flow is not
observed determine reason for lack
of flow and repair as necessary.
10. Radiator or A/C condenser fins
are dirty or clogged.10. Clean insects or debris.
11. Radiator core is plugged or
corroded.11. Replace or re-core radiator.
12. Fuel or ignition system
problems.12. Refer to Fuel and Ignition
System group for diagnosis. Also
refer to the appropriate Powertrain
Diagnosis Procedures manual for
operation of the DRB scan tool.
13. Dragging brakes. 13. Inspect brake system and repair
as necessary. Refer to Group 5,
Brakes for diagnosis.
14. Bug screen is being used
causing reduced air flow.14. Remove bug screen.
15. Thermostat partially or
completely shut. This is more
prevalent on high mileage vehicles.15. Check thermostat operation and
replace as necessary. Refer to
thermostats in this group.
16. Electric cooling fan not
operating properly.16. Check electric fan operation and
repair as necessary.
17. Cylinder head gasket leaking. 17. Check cylinder head gasket for
leaks. Refer to testing cooling
system for leaks. For repairs, refer
to group 9, Engines.
18. Heater core leaking. 18. Check heater core for leaks.
Refer to Group 24, Heating and Air
Conditioning. Repair as necessary.
7 - 8 COOLINGPL
DIAGNOSIS AND TESTING (Continued)
