I have this problem. When I drive home after a long commute, I have really, really loud wheel noise (loud like impossible to ignore, turning your head on the street kind of noise). This only happens when I am driving 40 minutes or more, and only on the last couple miles to my house (which happens to be several miles of downhill driving with a fairly steep grade towards the end). The noise continues to persist, even at very low speeds once I get into town. If I let the car sit for just five minutes or so, the noise goes away.
This doesn't happen every time I drive home. It might depend on environmental conditions. It won't ever happen if I just go for a quick drive up and down the hill. The dealership has not been able to find anything wrong with it or come up with any explanation. This has been happening for over two years, it's a 2013 Honda hybrid, bought new. I've speculated if it could some brake-related issue that only manifests when braking regeneration is suppressed when the battery is full. Has me at my wit's end. When I get home from work the dealership is closed, and even if I could make it into the dealership with the thing clanking away, by the time I could get in and talk to someone the noise would go away unless I had them on the phone and ready to hop into the car at a moment's notice. So much for the warranty.
I had the same problem. After unsuccessfully trying several garages to fix it, I learned how to fix cars myself (read lots of blogs, watched video on YouTube, read a couple of books) and redid the whole brake system: disassembled the caliper, cleaned everything thoroughly, changed brake pistons, changed sealing rubbers and dust covers, installed new brake disc and brake pads, new brake pin (greased it with the appropriate grease). Problem went away.
It was a rusty/incorrectly installed brake pin. Sometimes brake pads wouldn't return after you stop pressing the brake pedal. After brake system rebuild everything moves smoothly and brake pads always return to the initial position - no more weird sounds.
Also, when changing the brake pads, I've noticed that one of the pads (that was failing to return) was much thinner than the others.
Problem is: when they change the brake pads in the dealership/garage, they don't rebuild the whole system or grease the pins properly. You will not notice and they're not paid for the extra quality work. So things like this happen quite often.
The only way to do everything properly is to do it yourself. In case of a brake rebuild it's not very difficult but very time-consuming. Most difficult part was to insert the new piston back in the caliper.
Without hearing it I can't say for sure, but do you brake intermittently or continuously while going downhill?
If the latter, it'll likely be a caliper & disk getting hot and expanding, and rubbing, which can make an almighty racket - and then when they cool again they contract, meaning that a cold inspection would reveal little.
Alternately it's a wheel bearing on its way out, but that's unlikely on a new vehicle.
Does it get any better or worse when you apply steering, or not change at all?
I purposely brake intermittently. But, the brakes are definitely very hot when I've checked them.
I had wheel bearing issues with a previous older car, under similar circumstances. I checked steering, it doesn't seem to make much difference. The dealership dismissed wheel bearings as a possibility and said they checked the CV joint.
Their only theory the first time around was a small rock or something getting stuck in there and working its way out. The old "mud in your tires" sort of thing I guess (Joe Pesci reference). That's a mighty devilish rock.
when reading this, and from my own experience, I think it are the brakes. But only that it also happens when you don't break continuously. Could it be a CVT geared car has a lot less resistance on the engine, even in the L position, compared to manually geared cars?
Disclaimer: I know little about the technical details of cars.
I don't know if it is the same noise, but I had a loud, fast paced, 'whoom, whoom, whoom' sound on my Honda Civic Hybrid from 2008 when going downhill a lot.
Living in the Netherlands (mostly flat) I only had this during holidays in less flat parts of Europe. Never thought much of it and when asking the dealership they never heard about the problem, but also could not see anything wrong with the car. And it only was reproducable in mountain areas, and took a while to surface...
Then after about 3,5 years, after a holiday, the sound was almost always present. Drove to the dealership and the brake discs needed te be replaced, they were 'square'.
I was not allowed to drive another mile (kilometer in my case ;) with the car.
I always brake as less as possible going downhill, and always use the L (low) gear position, but can't prevent it. The roads in the Swiss Alps are so steep, only low gearing does not help, at least not with a Civic Hybrid. I don't drive with my foot on the brake all the time, but pump the brakes when really needed.
(in comparison, the Seat Ibiza Diesel car I had before could slow down a lot better in low gear, almost no braking was needed, but when going downhill with the Civic in low gear, it goes faster and faster, until you just must brake. Also the Ibiza was manual gear, like most cars in Europe, the Civic had a CVT)
The dealership thought it could be a result of the brakes getting hot when going downhill (cannot be prevented) and then keeping the foot on the brakes when standing still deforms the braking discs.
Using neutral gear position and if needed the handbrake when stopped, could be prevent it from happening again.
After replacing the discs I drove the car another 1,5 years until October 2013 and never heard the sound again.
Depending on the hill gradient and if it's safe, you could try going downhill on the commute using just engine-braking (use a low gear) rather than riding the brakes. This could help determine if the problem is brake-related or not.
Unfortunately it takes long enough to reproduce and is unreliable enough that I'm not willing to do enough trials relying on just engine-braking that I would be able to draw any firm conclusions. I have tried relying on gearing and I suspect it has something to do with the brakes but I don't know.
The last stretch where it goes down to 40 and then 30 is steep enough that engine braking without any brake pressure at all is not going to happen safely. And there are lights too, I almost always (but not always) hit at least a couple of them coming into town, so stopping is kind of mandatory there (and unpredictable).
I don't have a habit of riding the brakes though, I'm either gently depressing them or my foot is off. But without gearing down there's going to be a significant amount of intermittent braking; just not continuous.
This doesn't happen every time I drive home. It might depend on environmental conditions. It won't ever happen if I just go for a quick drive up and down the hill. The dealership has not been able to find anything wrong with it or come up with any explanation. This has been happening for over two years, it's a 2013 Honda hybrid, bought new. I've speculated if it could some brake-related issue that only manifests when braking regeneration is suppressed when the battery is full. Has me at my wit's end. When I get home from work the dealership is closed, and even if I could make it into the dealership with the thing clanking away, by the time I could get in and talk to someone the noise would go away unless I had them on the phone and ready to hop into the car at a moment's notice. So much for the warranty.