Horrible screaching noise - Started suddenly

[Doc]

I have only had this car for a few weeks ('78 Spider). It has driven fine, has clean oil and no big leaks, and the timing belt looks good. But all of a sudden, yesterday it started screaching unrelentingly. It started VERY suddenly and was VERY loud. I shut it off immediately and rope-towed it the 1/2 mile I was away from home. In the garage I have started it twice for only a second or two and the sound is awful. I recognize it as probably shot bearings somewhere . . . but where? How do I diagnose the source of this noise. Any suggestions from the experts?
Thanks

[pope]

First I would take the belt off the alternator. See if that works. Screeching is usually a belt condition. But then you say that you think its bearings? Bearings sound way different then screeching. Bearings are metal grinding sounds. Screeching is a sonic wave pattern that is caused by rubber slippage.

See is the alternator belt removal helps. From this you will find out two things. If the belt is producing the screeching and if the alternator bearings are going.

Good luck

[So Cal Mark]

if removing the belt doesn't help, try depressing the clutch pedal to see if the release bearing is frozen

[Ernie]

After doing the easy things already suggested, check to see if the timing belt tensioner is the source of the noise. When that thing freezes up bad things can happen -- broken or tooth jumping timing belts = bent valves.

[Doc]

Thanks Pope, Mark, and Ernie. I checked the alternator cable and that was not the problem. In the process, however, I noticed that the air pump was not turning at all and the source of the noise was the crankshaft pulley turning against a stationary fan belt (which was on entirely too tight). Because the belt was already becoming fried at the spot of the pulley, I cut it off and solved the noise problem. Now, I have read from other post on this site that the air pump is an emissions component and that some Fiat owners not subject to testing (like me) have removed it. Correct? If so, do I need to remove it, or is simply having it's drive power disconnected good enough? Right now I am just relieved to know that I did not have something more seriously wrong with my engine. I guess I overeacted when it happened, but it was louder and more terrible sounding than any belt issue I have ever heard before.

Thanks, this website is wonderful!

Doc

[So Cal Mark]

just removing the belt makes the air inj system inoperative. I'd suggest removing the pump and all of it's plumbing when you get time.

[pope]

I thought it was a belt. I forgot about you pollution control air pumps on the late 70's models. Glad you found it. At least we got you looking in the right direction.