Vibration/hum at idle when brake pedal released

[Royalstorm]

I recently noticed that my Stinger, which only has 400 miles on it, sends a subtle vibration/audible hum through the armrest when moving from a complete stop as I gently take my foot off the brake. When first driving from a cold start, there is no abnormal noise/vibration. After driving for 5-10 minutes, I begin to notice the hum. It’s subtle if I quickly release the brake at a complete stop, but more pronounced if I very slowly release the brake pedal, as in pulling into the garage to park. I haven’t noticed any changes in braking or sounds while braking. Only abnormal when letting off the brake at a complete stop. Idle stop/go and auto-hold are off.

Anyone else noticed this or willing to try to replicate in your Stingers?

 

[Kia Stinger]

Moved into the main area for more views...

 

[Royalstorm]

Moved into the main area for more views...

Thanks!

 

[Royalstorm]

Also, I don’t seem to notice the hum/vibration if just driving in town even if for longer periods of time. But even 5 minutes of highway driving and the hum/vibration is noticeable after coming to a stop and then taking my foot off the brake.

 

[Royalstorm]

I only have 400 miles on my Stinger GT and have noticed a vibration/hum that occurs when the brake is slowly released after a complete stop. This seems to only occur after highway driving, when I slowly creep forward at idle. Have you noticed anything like this?

 

[StingMe]

I only have 400 miles on my Stinger GT and have noticed a vibration/hum that occurs when the brake is slowly released after a complete stop. This seems to only occur after highway driving, when I slowly creep forward at idle. Have you noticed anything like this?

Sounds like brake hum. The pads and rotors are hot.
On slower stops, the brakes aren't applied fully, which allows the pads to vibrate against the rotor surface.
Usually no service is required as the noise is unavoidable.

 

[mldavis2]

I find the brakes to be interesting. There seem to be two switches on the brake pedal (I haven't crawled under there to count them). One turns brake lights on and disables the cruise control, the other lower switch controls the Start/Stop feature. The brakes are also power-regulated to increase pressure when the big Brembos on the GTs fade a bit. So it may be either a vibration from the Auto Start/Stop computer function, or it may be the change in brake pedal pressure modulation as the brakes no longer need extra assist after a hard stop.

 

[Royalstorm]

Sounds like brake hum. The pads and rotors are hot.
On slower stops, the brakes aren't applied fully, which allows the pads to vibrate against the rotor surface.
Usually no service is required as the noise is unavoidable.

So in brake hum, you’d expect the sound when first releasing the brake after a complete stop?

 

[Royalstorm]

I find the brakes to be interesting. There seem to be two switches on the brake pedal (I haven't crawled under there to count them). One turns brake lights on and disables the cruise control, the other lower switch controls the Start/Stop feature. The brakes are also power-regulated to increase pressure when the big Brembos on the GTs fade a bit. So it may be either a vibration from the Auto Start/Stop computer function, or it may be the change in brake pedal pressure modulation as the brakes no longer need extra assist after a hard stop.

Interesting. Thanks for the comments. What seems odd to me is the lack of hum/vibration even after driving/braking for a long time in town. But even after 5 minutes of highway driving and soft braking, vibration recurs after starting from a complete stop. This makes me worry about some other mechanical problem that is only seen after driving at higher speeds with higher wheel revolutions. I’m having the car looked at tomorrow to ensure brakes/rotors/etc are ok.

 

[Royalstorm]

Update:
I took the car in today to the dealership. I was able to replicate the vibration/hum for the technician after a short drive. He did inspect the brakes and felt that the hum is normal and secondary to the brake pump. I asked if they would let me take one of the other stingers for a drive to compare and was able to take a GT1 for a 5 mike highway trip. After multiple stops, I couldn’t appreciate any hum or vibration, so I have a hard time believing this is normal. I called Kia directly to open up a case. Any other recommendations?

 

[Kia Stinger]

I called Kia directly to open up a case.

I think that's a good start. Let's see if you get anywhere there. I have a feeling there's an issue somewhere as I don't see anyone else talking about a hum or vibration...

 

[StingMe]

Update:
I took the car in today to the dealership. I was able to replicate the vibration/hum for the technician after a short drive. He did inspect the brakes and felt that the hum is normal and secondary to the brake pump. I asked if they would let me take one of the other stingers for a drive to compare and was able to take a GT1 for a 5 mike highway trip. After multiple stops, I couldn’t appreciate any hum or vibration, so I have a hard time believing this is normal. I called Kia directly to open up a case. Any other recommendations?

Stinger used for comparison did not have the same mileage and same braking use history.

There may be some glazing of the pads and/or hot-spot deposits on the rotors.

Service COULD sand the rotors to remove deposits and replace pads.

Be sure to brake lighter than usual during break-in period.

 

[Royalstorm]

Stinger used for comparison did not have the same mileage and same braking use history.

There may be some glazing of the pads and/or hot-spot deposits on the rotors.

Service COULD sand the rotors to remove deposits and replace pads.

Be sure to brake lighter than usual during break-in period.

Yeah, the mileage on the GT1 I drove is lower for sure, so that certainly could play a role. I’m still trying to make sense of how this is a brake pad issue though. I don’t notice any vibration even after 10-15 minutes of in-town driving. But 10 minutes of highway driving with slow engine-braking and light application of the brake pedal at the off-ramp will cause the vibration to surface.

 

[Royalstorm]

I think that's a good start. Let's see if you get anywhere there. I have a feeling there's an issue somewhere as I don't see anyone else talking about a hum or vibration...

Yeah, I agre. The variability of the sound/vibration only occurring after highway driving doesn’t seem to match with a brake pad or pump issue. With that said, I’m certainly no mechanic which is why I’m posting here to get other thoughts and opinions.

 

[Royalstorm]

Update:
Dealership has been in contact with Kia. They are requesting another look, planning to keep the car for 1-2 days to do some more diagnostics.

 

[Royalstorm]

Update.
Chassis ears apparently suggested the sound was coming from the center muffler. They replaced it today without any noticeable. Same vibration is occurring after the repair.