Squealing noise?

[TTownEP]

I’ve been having some stuttering and back-firing issues this past week. My buddy from work (very knowledgeable) went for a ride to help diagnose. We thought perhaps it may be junk in the fuel inlet on the carb, since apparently this truck has no fuel filter(?!) from the previous owner.

I grabbed a Mr Gasket in-line fuel filter from the parts store, some 3/8” line to replace the braided stuff, and a new fuel pump, just since I was in there and it looked quite rusty and corroded.

Got it all plumbed and installed and had my wife run the starter for a bit with the coil unplugged to prime it up and check for leaks then hooked it back up and went for a drive. I’m getting this squealing noise now at above-idle speeds. It doesn’t quite sound like a fan belt (which I replaced both of last week) to me, but help me out here. What is this noise?

https://youtu.be/yXf7XtPn-0o

 

[TTownEP]

1972 with power steering added, 302 with Edelbrock carb


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[DirtDonk]

Fan belt for sure. Because of all the cranking your battery would have needed some serious re-charging from the alternator. With it being more than normal, it very well could be the alternator.

In fact it's more likely the load on the alternator than anything else. The power steering does make odd noises, but not often from the belt slipping. Usually it's the pump itself.
The squeal when you goose it and the quiet when you let off is classic alternator slippage.

Paul

 

[DirtDonk]

The immediate cure is to charge the battery overnight and see what happens when you start it the next time.
But once it's happened, it can often squeal more easily than before. A little glaze on the belt and some on the pulley groove and you may need to tighten it up a little more.

You can even test the belt theory by spraying a little water on it when it's doing it's thing. If it goes away, gets worse or otherwise changes it's tone when you hit the belt with water, well there's your problem.

It will "usually" go away on it's own once the battery has caught back up and the alternator is not being required to put out a heavy charge. Usually when there is no choice but to drive it, this will take from a few seconds to a few minutes to dissipate.
But it may come back now and then until things are back to normal.

Good luck. Hopefully yours goes away without too much work.

Paul

 

[DirtDonk]

Sorry, forgot to mention that yes, it can actually be other things helping it along. Even if it's indeed the alternator, a worn out water pump bearing will make it worse. Or an old tired power steering pump will contribute as well. But it's usually at it's worst when the battery is low, and is almost always brought about by the alternator load.

Paul

 

[TTownEP]

Dang. I had no idea the load on the alternator pulled that kind of resistance on the belt. Charged it up while I was getting ready for work, and it’s quiet now.


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[DirtDonk]

Oh yeah, and the bigger they are the harder they are to turn when under load.
But the main culprit is likely the smaller pulley sizes usually on them. A power steering pump would seem to require more to turn, but they have those really big pulleys too.
The larger diameter not only gives more leverage, but at the same time there is more surface area for the belt to grip.

My F350 with the same alternator as the old Broncos had a larger diameter pulley. Perfect for when I swapped to a 100amp large-case alternator. On the Bronco I got belt-squeal until I went to a dual groove pulley. On the pickup I didn't have the issue.

Paul