My 99 Nissan Sentra will not start.new. I The car is not turning over at all.its making like a whining noise but not from a dead battier. best way i can describe it is free spinning What could the problem be?

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i would first check your surpentine belt to see if it is getting burnt up, most whining sounds are an indication of a bad pully either from the alternator,compressor, pwr steering pump, tensioner, idler pully,ect.ect., i would take the belt off and spin the pullys by hand untill you find wich one is bad

Have diagnostic codes read at a local shop or auto parts store and go from there. noise in back is fuel pump, it's probably ok, most make a whining noise. Probably needs a complete tune up or some minor repairs. guessing will not help. have someone qualified help you.

Where on the car is the noise coming from?
How many miles on the car?
Rattle? Grinding? Whining? Knock?

starter is probably locked up. if you need more info to replace and check let me know

It is best to weld this back in place, sometimes you'll nedd an extra piece of pipe to correct this problem

Most likely a dead starter motor

you call it the serpentine belt, we call it the fanbelt.it,needs tightening,slightly loosen the alternator, then pull away from engine and tighten belt, tight enough when you can move longest part of the belt, between pulleys, 1/2 inch in/out.
if squeel re occurs fit new belt.

sounds like a case of closing the horse after the barn ran away...Pretty good chance that you have lost an engine bearing (yes, that means it's new engine time)
To avoid this in the future regard your oil light as a "you just blew your engine" light. Check your oil at least every two weeks, and this will never happen again (not for lack of oil anyway!!!)

whinning sound not from the timming chain it would be a deeper noise alternator belt does that often belt loose and worn out when its cold slip on the pouly and finally grap when its warm if you have any other question ill be honor to help you im pierre from montreal hope it help fixya the post