Long story, but trying to give full background.

I am hearing this sort of rhythmic sound when driving. It's not a loud sound, and I'd estimate the frequency to be around twice per second. There is some correlation with speed, but not a 1-to-1 tracking to my ears. It's too slow to be a tire rotation thing. And to replace a dead TPMS sensor, and get rid of the run-flats it came with, I had both new (Lexus) wheels and tires put in and the sound didn't go away. It doesn't seem to change if I steer to the right or left (loading/unloading front wheel bearings).

At normal (for me) stereo levels I can't hear it, and on noisy road surfaces I can't hear it. But on a smooth surface asphalt road it's there. I can't really say if it's there below 30MPH (I can't hear it then anyway). And above 45-50MPH it either stops, or the wind and road noise combined make the sound fade into the background. I have no unusual vibrations in brake pedal, or steering wheel, or by seat of the pants, no off-center pull in the steering. Basically, the car is going down the road in fine fashion except for this noise.

I thought maybe the brakes (rotor run-out). I have a Quick Jack, so I raised the car and took off all 4 wheels to check the brakes. They were nearing the end of life so I swapped out rotors and pads on all four ends. While I had the rotors off, I spun the hubs and found the right front hub had a spot that had more friction than the rest of the rotation (but no noise and hand rotation speeds). So, my suspicion was a wheel bearing was going out. Note, there isn't any grinding sounds, and I checked for in/out play, as well as grabbing the wheel and seeing if there was any side to side or up and down play with none found.

I took it in to a local shop to have motor mounts replaced and to see about the sound. Their tech said he couldn't hear the sound, but it was raining that day and that might have been enough to mask the sound when he took it for a test drive. He also did all the pushing and prodding things and told me it might be in an early stage of bearing failure but he didn't think so and there was certainly no safety issue. I might also mention the PO had never had the airbag recall done, so while it was in for that I asked the Lexus dealer to do a safety check and they reported all was good on that front.

I went home, raised the car, and made sure all the underbody plastic splash shields were in place and tightened down. They are.

I'm fortunate enough to have three vehicles, but still my wife would like to take it out - maybe go top-down driving to the mall with one of the grandkids. I'm not allowing that until I know for sure this isn't somehow going to turn out to be "wheels fall off while driving" sort of thing regardless of the dealer or local mechanic. Paranoid - yes, but I like to error on the caution side.

I need some ideas of thing to check.

 

Could one of your cooling fans be going out intermittently?

 

you could bring it by my house and I could provide my two cents if you like…I am half a mile from ToyLex

 

That's a very generous offer. If I haven't figured out something before the holiday has come and gone, I will PM you to check on your availability.

thanks,
Lee

 

I have had it sit idling from cold to normal level, and never heard the fans do anything peculiar, but still a free test is always worth a shot.
Since I'm in Florida, the AC stays in the ON position virtually always. I will try a drive with the AC off, and before the engine gets fully warmed up - let it go through it's warm up cycle and see if anything changes.