ml30306

Hello,

I own a 2004 Lexus ES330, mileage is about 120K. For over a year I have had a vibration noise come from behind the dashboard. The sound is like a light rattle. I have been to 2 Lexus mechanics who could not identify the problem. Both stated that the source was around behind the center dash near the firewall. Here the facts I know about the noise:

- Loudest when in Park when I start the car
- The sound goes away once the car passes ca. 900-1000 rpm.
- When in Drive at e.g. a light or fully stopped the noise is there once I pass 900 rpm, then it is gone
- When not moving and hearing the sound it will also go away once I turn the steering wheel in either direction, will then come again when I stop the steering motion
- Noise usually goes away after a while BUT when stopped on a hill driving slowly upwards the noise it very noticeable (maybe when kept exactly at the 900 rpm point)

Any thoughts on this?

Wendles

I had a VERY similar thing happen in my 2005. Everyone said "dash rattle, ignore it", but it was making me CRAZY. Then one day... I opened the hood. There was a metal hook-like bracket to the left touching the firewall between the engine bay and dashboard. When the car was on or turning or revving it was vibrating against the shield, making that awful sound.

Huge chance that that is your problem. The remedy was putting in a new bolt. Hope that helps! Made an account just to answer this haha!

ml30306

Hi, I checked and saw a reverse black metal hook on the left side facing the engine, but it is firmly placed. Any chance you have a photo or can pinpoint the location? I just took out the AC and radio, still can't find the noise. The noise also goes away the warmer the engine gets, I am pretty sure that the noise is on the inside of the firewall somewhere.

Wendles

If you open the hood and stand in front of the car, it would be way up and sort of in the left corner. It should be firmly in place touching/almost touching the engine. Mine was not, and was instead leaning against the firewall and I could move it around with my hand.

ml30306

Hi,

I actually captured the sound, here the link:


You will see that at the end I stepped back on the gas and the noise immediately disappeared.

Wendles

Sorry, I don't have any other ideas ! Does the AC seem to affect it at all?

ml30306

Not from what I can tell. Turning it on or off makes no difference.

mmatheny

Sounds like a 60 cycle hum!!

speedkar9

Is your HVAC fan turned on by any chance?

Megafast13

Wow that is crazy. Would do a very thorough inspection under the hood, but kind of sounds like it's inside. Remove your stereo and see if you can get a better idea. With the radio out you have quite a view of the interior. Would think hvac fan motor, but I don't think it'd be that drastic of a change based on idle and rpm.

ml30306

Hi, I did remove the radio and AC units, could not identify the source of the noise, must be even further behind. Any idea what is behind the air ducts and yet still in front of the firewall?

speedkar9

Servo motors for the air ducts? Heater core? Nothing moving that I can think of.

Are you sure its not coming from under the hood? Could it be a loose plenum bracket that resonates with engine idle?

ml30306

Hi, no, the sound is coming from inside the cabin and not under the hood. The mechanics that tried to find the location also said that it was inside the cabin.

I did some troubleshooting yesterday. The moment I move or even slightly turn the steering wheel the sound changes. It is the strongest when the wheel is turned straight, the moment I turn it left or right the sound changes or even disappears. I also noticed that when I drive over e.g. a speed bump something on the steering wheel rattles. I now wonder if there is a component on the wheel column that has become loose and now hums at around 900 rpm. Any idea what that could be?

PFB

Just a heads up. Many owners, including experienced mechanics have been totally fooled by the origen of a sound. Sometimes it could even originate from the back of the car, while ALL are convinced it's coming from the front.

Keep at it. You'll find it eventually. Also don't forget to consider loose/rattling exhaust components.

Phil

jenga

The noise maybe coming from the inside but it is tied to the engine rpm / trans / exhaust. / steering. Something is vibrating at the low rpm and something in the cabin is touching something just right to respond to it.

Try and use a mechanics stethoscope (or length of hose and listen at one end) and poke around at different spots to find to see if you can isolate the sound to a certain area.

You mentioned the uphill at low speed it is really loud. My guess is a motor / trans mount is going bad or has failed and when the power-train tilts slightly back and makes a stronger contact.

With the hood up and in park, keep you foot on the brake and then run from reverse to drive / back and forth and see how much the engine moves tilts forward or back. Does is want to tilt even more if you give it some gas?