My daughter's 1997 Malibu sounds like it has crickets in the engine just when she first starts it. After driving for a few minutes it goes away. My husband replaced the idler pulley - didn't seem to help. From different forums I see it could be the tensioner, water pump - how do you know which one it is?

My 99 Malibue (4-Cyl w/103K miles) had a serious chirping/chatter sound as though the alternator bearing was failing. I took it to my friendly dealer who said the alternator needed relacement to the tune of over $450. Reacting to that as though it were a bee sting, I declined the repair, took it to local independent garage who said it was a belt tensioner. Problem solved.
Beware GM srvice garages (get a second opinion)

local independent garage who said it was a belt tensioner. Problem solved.

Yeah, I agree. My other car is a Jeep Grand Cherokee, and although it's not a chevy, it experienced the same problem. I tightened the belt a little (less then a half turn), and it sloved it perfect! Haven't heard a squeel since, and this was over a year ago.

Beware GM srvice garages (get a second opinion)
Also agree:nono:

No offense but you have your terms mixed up.

The idler puller is a belt tensioner and vice versa. This car has a spring loaded tensioner and once the spring becomes weak, it needs replacing. I have the same noise problems and it could be any one of the pulleys you see under there. It's no big deal, but it's embarassing to drive. Wait until the sound becomes louder and permanent, then try to find out the problem. Don't replace parts based on guesses and forums.

to determine which belt driven accessory is causing the noise, do the following.

1. Take the belt off and spin each pulley by hand, any that fell gritty or have side play (wobble) need replacing.
2 If nothing is found is step 1, spray each pulley's bearing (one at a time, otherwise, you can't narrow down the offending part) and re-start the engine. When the noise quits, you found the problem accessory. Replace the part that stopped squealing when you sprayed it.

I too had the same problem when I had my Malibu. I absolutely could not figure out where it was coming from. My guess was it was the alternator bearings. The dealer agreed and said it was the beginning of the end for the alternator. They wanted a little over $600 to replace it. (it was under warranty still). I figured I owuld just keep driving until it dies. It lasted until I traded the car in (abot 55K miles later) and the chirping became sporadic and it hardly ever did it anymore.

I don't know she has fixed the problem or not, but I am writing this to share with other Malibu owners. In my case this noise was not constant, so I just wait until it gets worse (Took me 1 year) and finally, noise was not going away. It was power steering pump bearing that makes noise.
I was sure that this noise is coming from one of the bearing in water pump, alternator or power steering pump, because belt tensioner has indicator line that shows the correct position and I have changed tensioner before. If you are lucky you can visually check the problem pulley. First, start the engine and stand in front of engine and than carefully look for a pulley that move left and right. There are suppose to be stay in position and when bearing is bad pulley is moving around.
Oh, another fix for noisy accessory belt. Apply coat of crayon on the belt. Noise is gone!