Jam008

Hi all,

I just bought my first Lexus (pre-owned, and regularly serviced). I have thoroughly enjoyed the driving experience of the NZ200t. I noticed whirring/siren sounds on slow acceleration. The sound is noticeable but not loud. It is most audible at lower speeds between 20-60km/hr. At a higher speed, the sound seems to disappear but may be lost in the ambient road and wind noise.

Initially, I thought it was Turbo sound, but it's getting a little bit annoying. The dealer advises that it's a normal Turbo sound. I thought surely Lexus wouldn't make an engine/turbo with that kind of noticeable whirring/siren sound. The sounds are more prominent when driven for the first time during the day.

I did some search and it does sound like the alternator failing sound that other people posted. However, I tested the battery when the car is running and the multi-meter reads ~14.2 volts.

I have recorded a clip of the whirring/siren that came on from the 10th second onwards(attached).

Thanks in advance and any feedback or advice is welcome.

LexMan2003

I listened to the audio clip. I have never heard such a sound in my 2000 NX. BUT, it does sound to me that the sound is there from the get-go (even before the 10-second point in your audio clip).
My first guess is that it is something in the turbo system, my second guess would be something in the transmission. Putting on my time capsule thinking cap, I VAGUELY recall an alternator making such a sound, but at a much higher volume. So the alternator would be my third guess. Also, just because the alternator is putting out the proper oomph does not mean that it couldn't be making any sounds. The same is true for many other components.
One thing you could try...when parked, car in PARK, hood opened, listen very carefully as you turn on many of the components (AC, headlights, etc.) and then rev the engine just a tad. See if you can replicate that sound while NOT actually moving. If you can, then the next step would be to have someone in the passenger compartment do the same, and YOU stand outside with the hood opened listening to try to isolate where the sound is coming from. Even if you are unable to replicate the sound, it couldn't hurt to have someone else in the passenger compartment doing the above while you try to hear the sound standing outside with your hood opened.

Another test you could perform...as long as you believe you're able to replicate this sound, go onto an empty road/highway and try to replicate this in a different gear. In other words, override the AUTOMATIC mode and put it into a particular gear. Don't go too fast, as you don't want to tax your transmission.

n0v8or

Too low a frequency to be turbo whine.
Noisy alternator bearings will not affect electrical performance. If coming from the alternator, a substantial electrical load change should cause a change in the sound. Try turning on the rear window defroster while recording the sound.

Jam008

@LexMan2003 Thank you very much for the advice. I will test a few more things as you have suggested. Really appreciated your help.

Jam008

@n0v8or thank you for the advice, I will test the alternator as you have suggested.

Roscol

I’ve had same noise on my since new 2018 and I’ve heard it on 2 different loaner NX’s. The whine slightly lags the increasing rpms’s which you would expect from the turbo.
Only happens on cold engine and while slight/medium acceleration.
Frequency is at a level that most won’t hear it unless on a smooth dead quiet , smooth road early in the morning.
I've even had people in the car at the same time who just can’t hear what I hear, i must have dog hearing or something, lol.

Roscol

The sound clip is exactly what I’m hearing, starts just after 10 seconds and continues on for 4 distinct segments of increasing/decreasing whine.
Definitely turbo whine on a cold NX engine.
Don’t worry yourself anymore, you’ll be chasing ghosts.

Jam008

@Roscol Thank you very much for your advice :-). my partner always complained that my hearing is bad as I cannot hear her properly =P. I asked my brother to sit in the passenger side to see if he can hear it. He said it's not loud but definitely notticeable.

I went out to test 4 Lexus NX200t over the weekend and none of the 4 cars exhibited the same sound as mine. One might have the whirring sound but would be ~5 times lower volume compared to mine :S.

Again, really appreciated everyone help in this :-)