348 squeaking at start up

Belt noise on start up is often the sign that a belt is a bit loose and needs tightening or replacement. If it has been 30K, replace it.

After driving my "new" 77 GTB home, without noise, (500 miles), the very next day, i started the car, only to hear belt "screech". The alternator belt felt loose, so I replaced it and the noise went away.

Spraying belt dressing, or worse WD40 on the belt(s) is only a diagnostic aid in determining the source, not a fix.

hth,
chris

 

could be the alternator or its tensioner bearing. this happened on my 355. Check the tension on the belt.

 

Don't feel stupid, John.

There's a pretty good chance that you do indeed have a loose fan belt. As Chris said earlier, spraying something on the belt can be used as a diagnostic tool to help identify the problem, but it won't fix anything. If you can start your car cold, when it's making the noise, and open up the engine lid to try to narrow down the area where the noise is coming from, that's your first step. If it does seem to be coming from the front of the engine, and down low, then it's most likely the alternator belt.

The 348 uses two flat, ribbed belts, one for the alternator, one for the A/C compressor. They aren't the same length. If you look at the diagram here, the A/C belt is "P", and the belt is tensioned in the conventional manner by loosening "A" and "E" and using "B" to pivot the compressor.

The alternator belt can become loose if locknut "C" on the tensioner backs off. The alternator does not pivot like the A/C compressor does, it is held in place with the upper and lower bolts, and the tensioner pushes up against the outer surface of the belt when you adjust bolt "D". You see the slot behind locknut "C"? The tensioner moves up and down in that slot - the nut remains stationary.

You need to get under the car and remove the splash panel, then check the condition and tension on the two belts. It's not easy because of the limited access, but the actual job of tensioning the belts isn't difficult. I replaced my alternator belt on my back in the driveway with simple hand tools.

Let us know what you find.
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I suppose I should add a couple of things to this, because I do not know your level of mechanical apptitude, and I don't want anything bad to happen to you or to your Ferrari.

1) You are going to need to jack up the back of your car and remove the rear tires, in order to remove the splash panel and give yourself some room to work. Safety first! You need a good jack, and you NEED jackstands - you NEVER work on the car when it is supported just by a jack - NEVER! You need to position the jack and the jackstands in properly braced areas of the subframe. If you're not comfortable with what you are doing, don't do it!

2) The belts are actually supposed to be tensioned with a special tool, but this isn't critical if you know what you are doing. You don't want the belts so loose that they slip, but you don't want them so tight that the bearings are overloaded.

3) After the belt is adjusted, you want to make sure that the locknut "C" is nice and tight so that the tensioner stays in place when you are done.

Others please chime in if I've forgotten something.