2003 Rav4.2 D4D Engine Noise

[Sensei]

http://www.youtube.com/watch?v=QrnM32zD3IA

What would cause a hissing sound like this? Slack/worn serpentine belt? I heard it for the first time a few weeks ago. It seems to happen more often when it's cold and wet outside, but this might be a coincidence. One day it's there, the next day it's gone. It does not stop even when the engine reaches operating temperature. The sound gradually disappears when the RPM increases, and it totally disappears somewhere around 1800-2000 RPM. The noise also sounds like it changes in pitch when enabling/disabling AC. I presume the compressor is connected to the serpentine belt?

[igormus]

http://www.youtube.com/watch?v=QrnM32zD3IA

What would cause a hissing sound like this? Slack/worn serpentine belt? I heard it for the first time a few weeks ago. It seems to happen more often when it's cold and wet outside, but this might be a coincidence. One day it's there, the next day it's gone. It does not stop even when the engine reaches operating temperature. The sound gradually disappears when the RPM increases, and it totally disappears somewhere around 1800-2000 RPM. The noise also sounds like it changes in pitch when enabling/disabling AC. I presume the compressor is connected to the serpentine belt?

hello mate

as for me - it looks like either clutch or A/C bearing is about to die with timing intervals (ON or OFF).

The idle RPM are stable. By the way what about driving belt tension unit???

Cheers/Igor

[SQUEALEYHEALEY]

Yeah, sounds like a Slack/worn serpentine belt? You could try adjusting the driving belt tension unit! But I would replace it, cos its a bugger to get at, you need to get or make a special tool to slacken & retighten the nut in the center of the adjustment pulley which is hard up against the inner wing. I cut the end off a socket & welded it to a bit of flat bar. Its easier to adjust if you take out the water expansion tank.

Cheers

[SQUEALEYHEALEY]

'But I would replace it'

Cheers

The Alternator belt is located behind the serpentine drive belt, which has to be removed to change the alternator belt. If they are over three years old their surface might well be worn smooth which will contribute to the noise & they are not gona last indefinately. I changed mine cos I did not want the hassel of them failing whilst driving.

[anchorman]

To check just pour warm water down over the belts.