Jeep Engines - Oljeep

4.7L POWER TECH V-8 3551. NoiseNote: It is normal for fan noise to be louder(roaring) when:The under hood temperature is above theengagement point for the viscous drive coupling.This may occur when ambient (outside airtemperature) is very high.2. LeaksEngine loads and temperatures are high such aswhen towing a trailer.Cool silicone fluid within the fan drive unit isbeing redistributed back to its normal disengaged(warm) position. This can occur during the first 15seconds to one minute after engine start-up on acold engine.Viscous fan drive operation is not affected by small oilstains near the drive bearing. If leakage appearsexcessive, replace the fan drive unit.Serpentine Drive Belt DiagnosisWhen diagnosing serpentine drive belts, small cracks thatrun across ribbed surface of belt from rib to rib (Figure 4-42), are considered normal. These are not a reason toreplace belt. However, cracks running along a rib (notacross) are not normal. Any belt with cracks running alonga rib must be replaced (Figure 4-42). Also replace belt if ithas excessive wear, frayed cords or severe glazing.Refer to the Serpentine Drive Belt Diagnosis Chart,‘Cooling System’ section of Chapter 4, for further beltdiagnosis. For serpentine belt routing, refer to Figure 6- 15.Figure 6 - 15STARTING SYSTEMThe starting system consists of the following components:BatteryStarter relayStarter motor (including an integral starter solenoid)Ignition switchParldneutral position switchWire harnesses and connections (including thebattery cables).The starting system components form two separate circuits.A high-amperage feed circuit that feeds the starter motorbetween 150 and 350 amperes, and a low-amperage controlcircuit that operates on less than 20 amperes. The highamperagefeed circuit components include the battery, thebattery cables, the contact disc portion of the startersolenoid, and the starter motor. The low-amperage controlcircuit components include the ignition switch, theparkheutral position switch, the starter relay, theelectromagnetic windings of the starter solenoid, and theconnecting wire harness components.Battery voltage is supplied through the low-amperagecontrol circuit to the coil battery terminal of the starter relaywhen the ignition switch is turned to the momentary Startposition. The parkheutral position switch is installed inseries between the starter relay coil ground terminal andground. This normally open switch prevents the starterrelay from being energized and the starter motor fromoperating unless the automatic transmission gear selector isin the Neutral or Park positions.When the starter relay coil is energized, the normally open relaycontacts close. The relay contacts connect the relay commonfeed terminal to the relay normally open terminal. The closedrelay contacts energize the starter solenoid coil windings.The energized solenoid pull-in coil pulls in the solenoidplunger. The solenoid plunger pulls the shift lever in thestarter motor. This engages the starter overrunning clutchand pinion gear with the starter ring gear on the automatictransmission torque converter drive plate.As the solenoid plunger reaches the end of its travel, thesolenoid contact disc completes the high-amperage starterfeed circuit and energizes the solenoid plunger hold-in coil.Current now flows between the solenoid battery terminaland the starter motor, energizing the starter.Once the engine starts, the overrunning clutch protects thestarter motor from damage by allowing the starter piniongear to spin faster than the pinion shaft. When the driverreleases the ignition switch to the On position, the starterrelay coil is de-energized. This causes the relay contacts toopen. When the relay contacts open, the starter solenoidplunger hold-in coil is de-energized.