• Damaged hoses
• Loose/damaged hose clamps
• Damaged/incorrect engine thermostat
• Damaged radiator hydraulic fan motor, fan blade
and fan shroud
• Damaged head gasket
• Damaged water pump
• Damaged radiator
• Damaged coolant recovery system
• Damaged heater core
If the visual inspection reveals none of the above
as cause for a cooling system complaint, refer to the
following diagnostic charts.
COOLING SYSTEM DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
PRESSURE CAP IS BLOWING
OFF STEAM AND/OR COOLANT.
TEMPERATURE GAUGE READ-
ING MAY BE ABOVE NORMAL
BUT NOT HIGH.
1. Pressure relief valve in pressure
cap is defective, or was not prop-
erly seated.
1. Check condition of pressure cap
and cap seal. Replace cap as nec-
essary.
2. Incorrect pressure cap was
installed.
2. Replace pressure cap as neces-
sary.
3. Incorrect coolant mixture. 3. Make sure a 50% by volume
mixture of coolant is used.
COOLANT LOSS TO THE
GROUND WITHOUT PRESSURE
CAP BLOWOFF. GAUGE IS
READING HIGH OR HOT.
1. Coolant leaks in radiator, cool-
ing system hoses, water pump or
engine.
1. Pressure test cooling system
and repair as necessary.
DETONATION OR PRE-IGNITION
(NOT CAUSED BY IGNITION SYS-
TEM). GAUGE MAY NOT BE
READING HIGH.
1. Engine overheating. 1. Check reason for overheating
and repair as necessary.
2. Freeze point of coolant not cor-
rect. Mixture too concentrated or
too diluted.
2. Check freeze point of the cool-
ant. Adjust the ethylene glycol-to-
water ratio as required.
3. Wrong cooling system pressure
cap.
3. Install correct pressure cap.
HOSE(S) COLLAPSE AS ENGINE
COOLS DOWN.
1. Vacuum created in cooling sys-
tem on engine cool-down is not
being relieved through coolant bot-
tle system.
1. Pressure cap relief valve stuck.
Replace as necessary.
INADEQUATE AIR CONDITIONER
PERFORMANCE (COOLING SYS-
TEM SUSPECTED).
1. Radiator and/or A/C condenser
is restricted, obstructed, or dirty
(insects, leaves, etc.).
1. Remove restriction and/or clean
as necessary.
2. Engine is overheating (heat may
be transferred from radiator to A/C
condenser). High underhood tem-
peratures due to engine overheat-
ing may also transfer heat to A/C
components.
2. Correct overheating condition.
ZB ENGINE 7 - 7
ENGINE (Continued)
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