'93 LS400 noise from engine compartment
 

'93 LS400 148,000 kms

Only after the car warms up after being on the road. When slowing down into quiet areas there is some noise coming from the front. There is no separate noise while steering. It coincides with the engine rev, it seems to increase in pitch when you accelerate a bit. It is also audible in park. It makes a sound similar to an electric motor.

Any ideas, thanks in advance,

Maybe a fan?

Unbelievably I just started having a similar issue in a 90 LS just at the cusp of crossing the 300K mark.

It sounds like there is a 2nd electric type motor under the hood & it has been coming & going but ran for a long time on my last outing today.

It does not at all sound like a fan clutch is going out & the rotating assembly of the 1UZ-FE sounds as stout as ever.

No clue what this could be?? Seems to be a tad harmonic in nature.

This seems to be something spun by the Accessory Belt that is starting to revolt.
Note: My Alternator is a couple months post replacement. Denso

yeah, I agree it is something spun by the accessory belt. And you only hear it on a quiet road.

I may go purchase a spare emergency acc belt because I think we must have a tensioner pulley about to quit.

Is it like a 'whirring' sound that follows the revs? Mine does it after it warms up. '98 with 200k. I'm thinking it might be timing belt related, perhaps the water pump or one of the idlers. I'm actually due for a water pump / timing belt replacement.

take your belt off and feel the pullys one at a time and you will probably find a rough bearing feeling in your fingers... replace it...

Was hearing some scraping sounds from my sons 96 LS400, and we took off the belt and ran the motor to isolate the noise, ran the car for 10 seconds, still heard it. I don't believe that it would cause any damage to run for a few seconds to see if noise is still there.

Very easy to take off belt on a 96, just put a 14mm wrench on tensioner pully and as you put turning pressure (CCW) the belt can basically slip off.