I have a 1997 chevy s-10 blazer, 4- wheel drive. My truck runs fine, it doesn't overheat, no dieing or stalling out. the noise at first sounded like crickets when your in the truck, then a sound like water flowing but muffled. Now when you open the hood and start it it sounds like clunking, or grating metal. ANY ONE HAVE ANY THOUGHTS ON WHAT IT MIGHT BE???????????????

 

Either Alt,idler pulley or tensioner pulley bearings are failing. remove the belt and check for play on those pulleys you can usually spin the alternator and feel if it's not right..

 

Leaning to tensioner pully as well.

 

Thank you for the responses but- I have actually changed the upper tensioner and the carrier wheel. could it be my timing chain, how would i check to see if the chain jumped or stretched?

 

could be the alternator bearings going to bad, takey it off and take it to the auto part store and have it checked..

 

I agree with the alternator. Blazers are the only vehicle I have worked on that the alternator bearings fail before the brushes/rectifier. I have replaced mine and 3 others for friends/family in the past 2 years for the same reason

 

Timing chains are not too common to go bad/stretch out on these, so I would rule that out. to find out if it is pulley related, remove the belt and start the truck *DO NOT LEAVE IT RUNNING LIKE THIS FOR MORE THAN A FEW SECONDS JUST LONG ENOUGH TO SEE IF THE NOISE STOPS*
If the noise stops, its pulley related, if it continues, start searching elsewhere

 

Pretty much exactly what I was going to say.