I had always thought that the top pulley was faulty because of the squeak when the engine is on (esp at idle, it goes away at higher revs). Anyway, while I was changing the coolant, I split some water onto the top pulley while refilling it with water at the inlet above the thermostat.

When I started the car, the noise went away - for about 3 minutes. All was very quiet. So when the noise came back after 3 minutes, I splashed a bit of water onto the belt and it quietened down again. So I guess one way to check if it is the belt or pulleys, is to splash or spray some water onto the belt and see if there are any changes.

Still I wonder what causes the belt to squeak.

 

Depending upon the noise you are talking about, I would not be too sure it is the belt. For example, a lot of V8 owners report a squeak from the tensioner bearing at idle (pic below). See if the squeak disappears if the car is put in neutral.

If it is the belt, BMA sells them for just over $20 - details at: https://www.clublexus.com/forums/sho...d.php?t=142455

 

Thanks for the tip. Do I have to change the whole pulley or can I just change the bearing.

Also, if it is the pulley, then why would water stop the noise? Perhaps it allows the belt to slip through the stiff pulley?

 

Either that, or the moisture actually increased the grip of the belt against the pulleys, eliminating the slippage and associated noise.

Here's all you need to know about the tensioner bearing. I replaced mine just this week:

https://www.clublexus.com/forums/performance-and-maintenance/59915-noise-in-the-engine-bay.html
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Thanks for the link. Looks like you just pulled the pulleys and greased it. Am I right? Did the noise go away? I assume that the lithium grease comes in a spray can.

I will do the same this weekend

 

Those bearings are sealed and it's not likely the grease made it inside, so it was a temp fix at best. You may as well replace the bearing, since it only costs $6 at NAPA, slightly more elsewhere.

Right now, I don't drive my car much, so it is hard to say if the noise is fully gone. As I mentioned elsewhere, I only really notice it when I am idling right next to a wall and I have my window down, and the only time that happens is when I am in the drive-thru lane at IN-N-OUT burgers.

So my involvement with this issue is proportional to my fast-food habit.