CONDITION POSSIBLE CAUSES CORRECTION
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
the Coolant section of this group and
adjust ratio as required.
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 Radiator Cap in this group.
Replace if necessary
(b) Hose between coolant reserve/
overflow tank and radiator is kinked.
Repair as necessary.
(c) Vent at coolant reserve/overflow tank
is plugged. Clean vent and 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
Cooling System Fans in this Group
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 Viscous Fan Drive
in this group.
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 Viscous Fan Drive in this
group for an explanation of normal fan
noise.
7 - 14 COOLING SYSTEM DN
DIAGNOSIS AND TESTING (Continued)
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