I have a 2016 Kia Ray, a small “box on wheels” kind of car – 999 cc gasoline engine. It is a South Korean model (not sold in North America), but I think my question is generic enough where that isn’t critical. It has disk brakes all around, and on the rear wheels it also has drum brakes only operated by the parking brake). The Kia mechanic told me it only has one fuel pump, located in the rear inside the tank.
The last few days, I’ve noticed a very faint “woo woo woo” sound coming from the right rear. It only happens when I start going in the morning, and only lasts about 10 seconds and I don’t hear it again. Today it also happened once mid-day after being parked for an hour or so.
I stopped by the Kia service center this afternoon, and asked them to check wheel bearings, brake pads, the rotors, and rear drums. The mechanic checked all those and couldn’t find anything amiss, and couldn’t reproduce the sound in a test drive (naturally). He didn’t check the fuel pump, although we both felt that was unlikely.
For now, I’m just going to keep an eye/ear on it and go back if it gets worse. Any other ideas of things to check?
I think that you should have the wheel bearings checked again–perhaps by a different mechanic. Try to find a mechanic who uses Chassis Ears to localize strange noises.
Good idea. This place is an official Kia dealer, but I confess that I squeezed my way into a super busy Friday afternoon shop schedule, and they might have not been as thorough as normal.
Also, bear in mind that the unitized body/chassis structure can “telegraph” noises to an area other than the exact place where the noise is originating. It’s entirely possible that the noise isn’t actually emanating from the right rear.
Except for the location, the description reads like the ABS check when you start moving forward. Maybe you could have a friend stand next to the right side door when you pull away and listen for which end the sound comes from. If you can hear it inside the car it’s likely someone outside can hear it too. When I first bought my 2017 Accord I didn’t hear the sound but eventually it appeared.
That’s interesting. Wouldn’t an ABS check happen all the time since day one? Or are you suggesting the ABS self-check is on its way out? I gotta say, the sound I described as a “woo woo woo”, is extremely soft and ethereal, almost like a ghost whispering. It is not the kind of sound I would think comes from an ABS system, but I’ve never heard an ABS except the machine-gun like sounds when it is working normally.
One more clue, which I forgot to mention, there have been some particularly heavy rains the last few days. I park in an underground garage, covered from the elements, but still it the air is heavy and dripping with humidity.
(1) strap my wife to the door and see if she hears the noise clearer as I’m pulling away in the morning.
(2) pay better attention for ABS sounds, maybe even study the indicators after the lamp-test gyrations at power up.
(3) consider that the sound is being telegraphed from elsewhere.
(4) get it back into the service center for a more thorough bearing check when they are less busy.
I’m still wondering if the parking brake might be at play, but these other ideas seem more plausible. Or I’m just looking for any excuse to hate on the parking brake, because I really don’t like that foot-pedal style.
-Chris
this business of sounds coming from the “wrong” place reminds me of a similar phenomena regarding roof water leaks (house or car). I know that many times the source of a water leak can be seemingly unrelated to where the evidence of the leak shows up inside, because of the crazy circuitous path the water can take back and forth on its way to staining your ceiling, wallpaper, and/or carpets.
That initially entered my mind, also, but I’ve never heard an ABS self-check that sounded like woo-woo. Then again, the “timing” of the noise is what I would expect for the ABS self-check.
I have had similar sounds coming from rear brakes… My theory is the brake pad and the rotor corrode a little bit in the moist air and the make this noise as the rough surface cleans up. If a car has been sitting a few days or weeks the rust buildup can cause a grinding noise when braking as the pads clean the rotor off — most have heard that. Light corrosion can cause these funny noises we sometime hear.
Brake pads rarely wear perfectly across the friction face. The edge can drag a little more than when the pads are brand new causing funny noises. I have had new pads do this as they bed in as well.
Keep an ear on it and it woo-woo turns into a light growl, that may be the bearing starting to fail. But the noise might go away on its own.
My vote is with @Mustangman 's explanation. If it was something like bearings, I’d expect it to continue for more than a few seconds. I would do as recommended, keep driving, if it stays the same it’s likely the rust explanation, if it gets worse, likely bearings.
Taking a vehicle to any shop for a noise that goes away within a couple minutes and only does it after many hours of sitting will be almost impossible to find, you will have to leave the vehicle over night with the shop…
I am another one for it sounds like moisture on the brake(s) burning off after using the brakes a couple of times… Cross rotating the rear tires, or just rotating the tires in general is a good test to see if the noise follows, if so - tire issue, if not - not a tire issue…
I had a similar noise on a Corolla, turned out to be the tire. If the tread is worn out, replace the tire. That has to be done in any event. Otherwise check for unusual wear patterns on the tread. Does the noise change depending on the vehicle speed? When coasting in neutral vs in gear? When turning, louder turning in one direction than the other ?
I would just rotate the tires front to back to confirm it’s the tire. Years ago though I had an intermittent rear noise in my wagon. Sounded like the left but the mechanic said it was the right. Hard to tell from the drivers seat. He replaced the axle and bearing and all is was well.
Also, while it would be impossible to rule-out a tire problem at this point, I question whether a tire-related issue would–somehow–disappear after only 10 minutes or so.
Whoops!
Yes, it apparently disappears after 10 seconds, which would seem to be an even better reason to doubt that it is tire-related.
The “woo-woo” noise isn’t like any ABS self-test sounds that I have ever heard, but the very brief nature of the noise, and that it only happens after a cold start, makes it seem more and more like an ABS self-test sound.
