4 ENGIN E SY M PTOMS DIAGNOSTICS 119
Coolant Over-Temperature
Symptom
When the coolant temperature is above 107 °C (224
°F), DTC 325 will be set and the control system will
command less fueling. A power loss may also occur.
When the coolant temperature is above 109 °C (228
°F), the red ENGINE lamp will be illuminated and DTC
321 will be set.
When the coolant temperature is above 112 °C (234
°F), the re d ENGINE lamp will flash, an audible alarm
will sound, and DTC 322 will be set. If the vehicle has
the warning protection feature enabled, the engine will
shutdown after 30 seconds.
Cause
• Low engine coolant level
• External coolant leaks
• Internal or external radiator blockage
• Broken/worn accessory drive belt
• Accessory belt tensioner failure
• Coolant t hermostat stuck (closed)
• Slipping cooling fan drive clutch
• Water pump failure
• Cooling fan blade assembly wrong/damaged
• Inoperative electric cooling fan
• Instrument panel gauge error
• Engine Coolant Temperature (ECT) sensor
biased
• Incorrect radiator
• Missing coolant thermostat
• Internal coolant leak
• Chassis effects, transmission, after-market
equipment
Tools
• Radiator pressure test kit and adapter
• Regulated compressed air
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM) with the rmocouple
Coolant System Inspection
Figure 135 Deaeration tank components
1. Deaeration tank cap
2. Deaeration tank
3. MAXIMUM coolant level mark
4. ADD coolant level mark
1. Check coolant deaeration tank for contamination
and correct fill level.
• If coolant leve l is low, do step 2.
• If coolant level is co rrect, do step 6.
• If coolant is contaminated with oil, go to “Lube
Oil in Coolant” (page 122).
2. Inspect for coolant leaks. Check for external leaks
from coolant hoses, radiator, heater core, engine,
or cylinder head cup plugs. Check for coolant in
oil.
• If any external leaks are found, repair
and fill cooling system. Test again for
over-temperature condition.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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