The fans in my 1983 nissan sentra just stopped.

check condition of drive belt and check tension of the belt as it may be slipping under load at revs.

Duplicate question.

If it is a rattling sound the starter may be loose, the starter bendix gear might be damaged.

If it sounds like a fan, it is likely the cooling fan.

If it is squealing, it is the serpentine belt. The idlers may be worn, their bearings may be dry- they make a chirping sound at slower speeds when they are dried out. Replacement is the best option.

Air pumps can sometimes make a thumping sound, and if certain emissions valving rusts through, it can be outright exhaust noise.

If it is a high pitch whine, that is usually the alternator. It is not a good sign when they begin to whine. Alternator bearings can also fail, and the sound varies.

Water pumps and fan clutches can also fail and they tend to make softer sounds. These can be checked by checking for radial play in each item with and without serpentine belt tension applied.

belts are to loose tighten them up

Sounds like a dry/failing bearing or power steering pump noise. You first need to try to track down where the noise is originating, and the most likely place is at the front of the engine.
I would start by listening with the hood up while parked with the engine running and the noise present, and seeing if it is coming from there. If so, the most likely cause is something connected to the belt - e.g. AC compressor clutch, tensioner, power steering pump, or generator. Can also be caused by the belt just slipping (warn out belt, tensioner not working properly).

Sound like the alternator bearings are seized or about to seize. The noise could be the bearings or the belt and the smell may be either of them also.

Seems like a drive belt problem, to confirm pour some water on belts the noise should go away or may get louder for a second. If either happens the belt or belts needs to be adjusted or replaced. Good Luck, If I fixed ya, leave me a FIX-YA comment thanks

its your engine belts need to change them. have a nice day

I have a 1999 Nissan Sentra that is smoking from the passanger side of the car's hood. It stops when I turn the air conditioner off