Bocatrip

My 01 LS430 has almost 125,000 miles. I am not the original owner but I know the timing belt was replaced at 95,000 by the previous owner (6 years ago) but am pretty sure the water pump was not. I just noticed after coming off a 20 minute highway trip and then onto city streets and idling what I would call a high pitch shrill sound. I thought at first it might be coming from another car, so I opened my window and the noise was louder. I proceeded down the road and the noise was gone. Then again a few blocks away at idle, i could hear the noise again and it continued at the same level as I drove off. It did not speed up as I revved the enigine. Then again, it stopped as I drove off and hasn't come back yet. It does seem to be coming from the engine area and I'm not thinking power steering pump because the noise is consistent regardless of engine speed.. The A/C being turned off has no effect on the sound either. That leaves me with alternator and/or water pump? Although the noise is not exceptionally loud it is very high pitch thus I refer to a shrill sound. There are no coolant leaks presently. Of course I will continue to look into it, but being intermittent makes it a little more difficult. Any ideas would be greatly appreciated. Thanks all.

jimbosr1

i had the same issue and i used a auto stethoscope and found it to be a bad belt tensioner and a bad alternator. i am thinking the tensioner put wear on the alternator.i changed both and been good for two years.if you end up changing your alternator change the tensioner at the same time because you have to unbolt the alternator anyway to change it.
i found the alternator because i smelt a slight burning smell which was one of the brushes in the alternator.

Bocatrip

Thanks, that's a start. If the tensioner or alternator why intermittent? I just came from a 40 minute ride with no symptoms or sounds. I was also thinking possible auxilliary fan? I'm not sure if there are two or one as even when I shut the a/c when it was making noise it was not affected. I'll continue looking into it. No music for the present time!

Tom57

Jim, if you know, was it the bearing on the pulley or the spring tensioner portion that failed on yours?

Bocatrip

I hate intermittent problems because when it's not there, you always hope/pray that it was a fluke, but mostly it's only a matter of time before the problem reoccurs. Broken things don't get fixed by themselves.

jimbosr1

i first changed the pulley but the sound came back in a couple of days.
i used a ratchet and socket and
loosened the v-belt and the tension was very little.
after i changed the tensioner there was a BIG difference with the tension.

jimbosr1

mine was intermittent too.use a stethoscope and put the probe on the pulley bolt while its running and if it tensioner is noisy its the tensioner .when a tensioner is failing it will damage the tensioner pulley and thats when you know it has failed.
replacing the pulley will cause wear on the other components ie water pump ,alternator etc.because the problem is still there.

Tom57

So replacing both tensioner and pulley assembly as a whole unit is the way to go.

jimbosr1

tom,when you buy the tensioner the pulley comes with it.you cant buy the pulley separate anymore.i would change the tensioner anytime the tensioner pulley is noisy.

Bocatrip

So after another day of driving I have been unable to duplicate the sound.

jimbosr1

boca,have you listened under the hood for any noise?have someone give it some gas while you listen under the hood then turn it off and see if you can smell anything like a slight burning smell.
it took a couple of months for the noise to be there all the time which got worse by then.

Bocatrip

Sometimes finding these phantom noises requires time and patience. If anything noises will become more obvious/louder and more frequent. When I first noticed what turned out to be a front wheel bearing, it was barely noticeable and my mechanic could not hear it and suggested I wait until it was more noticeable. 1,000 miles later my girlfriend commented on it and my mechanic was able to identify it. My concern with noises besides annoyance is the failing part leaving me stranded. I'll keep pursing this one and keep the forum posted. I have a wooden broomstick handy in my trunk the next time the noise shows up to help with locating the sound. Thanks everyone.

Arcturus

Did you check the serpentine belt itself? If they are cracked or glazed they can produce all sorts of sounds.

Bocatrip

I'll certainly give it another check, but last time it looked great, no cracking or dry rot. This noise was quite unique... can't put my finger on it.. almost electronic....

hyperopt

Worn or loose serpentine belt will produce squealing sound and the sound will vary depending upon the engine's RPM. If Boca's observation that the noise doesn't vary with engine's RPM is correct, then he can pretty much rule out the source of the noise is coming from rotating bodies driven by the engine.