
BASIC TROUBLESHOOTING
Abnormal Coolant Temperature Symptoms and Probable Causes
Probable Causes
Above
Normal
Below
Normal
Restricted cooling system passages X
—
Restricted radiator core passages X
—
Slipping fan drive be lts X
—
Faulty temperature-controlled fa n X
—
Obstruction in front of radiator or intercooler X
Low coolant level X
—
Damaged hoses X
—
Faulty thermostats X
—
Faulty water pump X
—
Faulty radiator pressure cap X
—
Air in coolant X
—
Thermostats not fully closed
—
X
Leakage around thermostat seals
—
X
Faulty temperature-controlled fa n
—
X
112 All information subject to change without notice. (Rev. 06/06)
DDC-SVC-MAN-0039 Copyright © 2006 DETROIT DIESEL CORPORATION
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