My 94 Blazer has been making a whining noise that comes from engine when cold and goes away when warmed up. It does this from idle and doers not get worse when driving or turning. It does go away once the engine warms up.
My mechanic just replaced the tension pulley and the water pump. The noise is still there. It is not as loud but still present.
Does anyone know what this could be?

 

Alternator???
A/C compressor??
Idler Pulley???

Take a dowel rod (wooden rod that can be found at walmart, home depot etc...or on a paper towel dispenser) and place one end on or close to the alternator and put the other end to your ear and listen to see if you hear the sound thru the dowel. The dowel acts as an amplifier and you can pin point noises and squeaks this way.

If you cannot hear the noise you described then move to another component and check it.

Of course use common sense when doing this and never put the dowel on the part of the pulley that is moving while the engine is running....Bad things can happen....

 

This is a great way to isolate sounds and keep track of failing bearings. I prefer putting whatever it is I am using dowl, screwdriver, etc. just in front of my ear where you can feel bone. You never know what can happen and I'd rather not have something stuck into my ear leaving me deaf. Be sure to avoid eyes as well. They do make technician stethoscopes which is a stethoscope with a metal rod. Harbor Freight or someplace probably has them for $10 or so.

 

You call it a whining noise...any chance it sounds kinda like a jet engine winding up? If so chances are the clutch on your fan has gone bad, happened to my '94 too with the engine off spin the fan by hand if it goes around more than one full revolution you found your problem.

 

I'm glad you all put the warnings in there, someone may have tried to place it on the fan blade while engine was running.