Detroit Diesel 4000 Series, Service Manual, Page: 2640 / 2706

SERIES 4000 12/16V SERVICE MANUAL
Engine Runs Cold and Fan Runs Continuously At Maximum Speed
Perform the following corrective actions to resolve engine runs cold and fan runs continuously
at maximum speed:
1. Fan clutch will not fully release.
Visually verify that the fan is not releasing and rotating at an idle speed. A free-wheeling
fan running at idle speed will create significantly less air flow (and noise level) than a
locked-up fan running at high speed.
To avoid injury when working near or on an operating
engine equipped with a hydraulic clutch fan:
3
Never work in close proximity to the fan.
3
Never try to keep the fan from rotating by holding the
fan.
3
Never tie down the fan with straps, chains, or other
restraints.
3
Never shut off the oil supply to the fan clutch.
To avoid injury when working near or on an operating
engine equipped with a hydraulic clutch fan, remove loose
items of clothing and jewelry; tie back or contain long hair
that could be caught in any moving part causing injury. A
hydraulic fan may start without warning.
Check fan release with a strobotac. Match-mark the fan and fan clutch pulley. Start
the engine. The two marks should not rotate at exactly the same speed. If they do, the
fan clutch is not completely releasing. Fan speed should be at idle with a cool engine.
Refer to section C 222.05.01C 222.05.01 .
Next, shut off the engine. The fan should rotate freely without engine oil pressure to lock
up the fan clutch. Go to step 2 for a further probable cause.
2. There may be electrical wiring problems.
Ensure tight connections, good grounding points, and no bad wires. Check all electrical
connectors to be sure none are broken, cracked, or damaged. Go to step 3 for a further
probable cause.
All information subject to change without notice.
E -10
Copyright © DETROIT DIESEL CORPORATION