Humming Ls 400

[amcdonal86]

By the way, the only way I've been able to make the noise stop is by jabbing the brakes hard (and holding them). However, the noise comes back as soon as I let off the brakes. I believe this eliminates any aerodynamics-related issues.

Also, in addition to shifting to neutral, I have shut off the engine while at speed--with no change in the noise whatsoever. I believe this eliminates any engine-related causes.

In my mind, it has to be related to the drivetrain or brakes. I do not believe it is related to tires, as my tires are perfectly balanced, and I feel no vibration when driving (unlike the OP). Anyone have any ideas?

[VBdenny]

Years ago, I replaced the strut rods on my car because the car was pulling to the right. I never had any vibration through. My car did develop a vibration which I could feel in the steering wheel but only between 75-85mph. When I replaced the tires with BFG Traction TA/V's, the vibration disappeared. The car is like glass right up to speeds I won't discuss.

[amcdonal86]

Any insights on the "harmonic" resonance?

[amcdonal86]

Well anyhow, I took a 500 mile road trip this weekend. The car continued to make the noise when I arrived at my destination, and also made the noise when I came home.

On a hunch, and also because my car was getting pretty dirty, I decided to take the car to an automatic carwash with a powerful undercarriage wash. To my surprise, following the carwash, the noise is completely gone!

I wonder what it could have been. Leaves? Twigs?

I'm crossing my fingers in the hopes that the noise never comes back.

[amcdonal86]

Blast! The noise is back. Doesn't seem as loud as before. I wonder if the noise stopped because whatever was causing the noise was wet from the carwash, and now that it's dry, it has started making the noise again.

[dpellet]

Like OLDLINColn, I would have the wheel bearings checked out as this is a common symptom especially at speeds above 25. Best of Luck!

[amcdonal86]

Is there a way that I can check them out myself?

[happy rider]

Can't agree enough with you. I had same problem with my LS430 after I bought it. The problem is, I keep thinking this is a lexus and I'm expecting a superior performance, at least a smooooooth ride from it.

So, why I can't escape the fate of getting a humming noise that usually came out from my noisy subaru ;)

SKperformance, interesting what you said about the alignment. Could be possible; I definitely should get that checked soon, because I don't want my new tires wearing poorly. You said you had the dealer "add pressure?"

Only one other person (aside from valets, etc.) has ever driven my car since I bought it, and I was in the car with him when he drove it. I don't have any kids :D . Personally, I drive VERY conscientiously and take care to avoid any kind of road imperfection, including potholes and utilities. Roads are pretty smooth where I live, and my rims are the standard 16" 5-spoke ones for a 1998 model. Haven't hit anything major I can recall recently, and certainly no curbs :o . I suppose I'll find out in about three weeks if a rim is indeed bent (when I get the new tires put on). At any rate, everything should be perfectly balanced right after the tires go on.

Marklouis, transmission mount? That's an interesting point. I can't emphasize enough how faint the sound I'm talking about it--I mean, it's really just "barely there." But if it persists after I get all the work done (I have a nagging suspicion it will), that'll be one of the items I check. Thanks!

[VBdenny]

Worm strut rod bushing will cause steering and tire wear issues but probably not humming. Almost every time I hear about it, it turns out to be the tires.

[dpellet]

Are you able to pinpoint a general location of the humming? ie. front/rear right left? If so a quick inspection of the wheels you identify at a brake/tire shop should be able to quickly le you know whether its tires or a wheel bearing.

The humming from a wheel bearing will change in audibility as speed increases or decreases but will be consistent and get louder as time goes on if it does not fail before that.

Wheel bearings are not to expensive and are quick to pack and install

[amcdonal86]

Thanks for that insight. I may do just that.

[amcdonal86]

BLAST.. Why won't the original poster respond to my PMs and emails!!!! He has the answer to my problem!!!!!!!

[amcdonal86]

I thought I'd follow up on this. It turns out it had something to do with the HVAC system, although I'm still not sure what. Perhaps a piece of detritus was lodged somewhere down the line.

I was driving 200 miles on the highway one day, and I realized that my HVAC wasn't blowing very hard at all. Even adjusting the temperature did nothing. Finally, I resorted to turning the fan on the highest setting. Still very little airflow. Then I began to cycle between different modes (face, legs, etc.) at high speed. Gradually the airflow was restored to its normal level.

Upon exiting the highway later, I realized that the humming sound was inexplicably gone! However, this would make sense, as the noise happened above a fixed speed threshold.

Does anyone else have some theories as to what happened? I'm thinking this would've made a great "stump the chump" moment for Car Talk.