Squealing coming from the front part of the engine

1995 FORD F-250
267,000 MILES • 5.8L • V8 • 2WD • AUTOMATIC
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MATTF250
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My truck has a loud squealing noise in the front part of the engine where the belt/pulleys are when I first start my engine. The voltage gauge on the dashboard shows about 11 volts with a loud squealing noise and then gradually rises past 12 volts which takes about 12 seconds of idling and then the loud squealing stops. When I turn on the defroster, head lights and wipers the voltage gauge soon moves down to about 11 volts and the loud squealing noise returns. I shut off the defroster, head lights and wipers and the volts go up past 12 and the loud squealing stops. What could be causing this loud squealing noise?
Mar 7, 2022 at 3:49 PM
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JACOBANDNICKOLAS
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Hi,

It sounds like the alternator belt is loose or worn. This vehicle has a single belt, and a serpentine belt. Tension is maintained by an automatic tensioner. In this case, I suspect one of three things is happening.

First, it could simply be the tensioner has failed and the belt is loose. Second, coolant or oil is contaminating the belt and allowing it to slip. Third, the belt has stretched.

I attached a pic below showing the belt, the tensioner, and the alternator. I highlighted the tensioner and alt.

Open the hood and first inspect the belt. Make sure it is clean, dry, and free of contamination. If it appears dry, with the engine off (of course) try to see if there is play when you try to move the belt. Does it seem loose?

Do this and let me know the results. Also, what is happening is the alternator, when under a load, is slipping on the belt. That is what you hear. Once it catches up to belt speed, it stops. When you apply a load on it again, you'll hear it again.

Do this and let me know what you find.

Take care,

Joe

See pic below.
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Mar 7, 2022 at 7:49 PM