My RDX started to make this noise or at least I started to notice it at around 20 mph. It’s a slight hum or buzzing lasts only a few seconds then goes away. I live on a hill so it happens on thr hill no matter if I go up or down the hill. I’ve also let off the gas when I heard it and the sound continues to happen. Once the car is warmed up and driven no noise. Any ideas on what it could be?

 

Need a bit more info. Where does it sound like it's coming from (or in other words which area of the car)? Does it sound like a rattle, or something more mechanical?

 

Sounds like it’s coming from engine bay. It sounds like a mechanical buzz like a buzzzzzzzz like I said happens maybe for five seconds max at around 20 mph when cold then after it does it once it doesn’t do it again

 

Here is a video of it so you can hear it. Right at 20 mph there is this subtle like buzz that happens for just a few seconds. Always at 20 mph

 

Out of curiousity, do you have any discs in your stereo?

 

I do usually have cds in yes

 

I wonder if that's the noise that you're sometimes hearing. I'm not sure if the sound would still be there if you took all the discs out and you drove for a bit...

 

Nope removed cds still happens two times. First and second time car hits 20mph. Stil sounds like coming from engine bay. I’m hoping it’s not tranny issues but I can’t think what else what do that when when it’s speed dependent

 

Possible bearing in a pulley or a pretensioner on the serpentine belt. Those noises are hard to pinpoint, unless you use a stethoscope-type device with the hood up and listen. And even then, it may not perform on demand for you.

 

Well that makes me feel a little bit better I was really concerned it was the transmission but I’ve kept up with maintenance I’ve done like fluid changes every like 10 K.

 

Did you ever figure out where the noise was coming from ?

 

You usually can hear the sound if it is associated with pulley or belts. The sound will go away after warm up.

 

No. I have a appointment to take the car in next month to a carmax where I bought it. It has also started a very very faint wine at stops like its winding down from something. I'm hoping its something dumb like a pulley and not tranny/TC related.

 

I have this same issue!! Its a slight humming/electrical whine noise that comes below 20mph when approaching a stop. It will humm loudly for 3-4 seconds and then go away. Please do let us know what the issue was so I and others who have this can take care of the issue!!

As a side note, do you have a rough downshift at 30 and 20mph while coasting to a stop? Like a sudden deceleration/rough shift shock, rpms rise and it doesn't have a smooth downshift? I am this issue I am describing and the whining and humming noise.

 

So yes I have had that rough downshift. One thing that can really help and cure that is to add a VCM muzzle. The VCM control the amount of cylinders firing. I bought a S-VCM off webstie. Came from Canada. Super super easy install. Takes minutes. You plug the device into the thermostat sensor and tricks the car to not allow VCM to kick in. Cured all my harsh downshifts!

I also had that wine when coasting to a stop. For me it turned out to be the Transfer case. I had it replaced just this week.