XC40 Rumble Strip Noise on Braking
Discussion
Wife’s new XC40 B4 is occasionally making a weird noise on braking. It sounds similar to running over a white line rumble strip.
It only happens occasionally. Has never happened below 45mph, when it happens its usually when braking with “medium” effort from around 60.
Braking lightly has never triggered it. Braking hard has never triggered it. Increasing or decreasing braking force when it does happen doesn’t stop it, but it will immediately go away on releasing the brakes or if the car has slowed to around 45mph.
There’s no feeling, not even a faint one in either the steering or the brake pedal.
These cars have a starter/generator motor with regen braking as part of their mild hybrid system. The belt drive for this hybrid motor looks brand new from above but its hard to get much view of the other side of the belt that actually drives against the pulleys. Car has around 200 miles on it.
The noise doesn’t change with steering input, it seems no more or less likely to happen regardless of braking in a straight line or with some steering input (tut tut, should be completing braking before beginning turning).
When sitting in the passenger seat, the noise sounds like it’s coming from the front left wheel. When sitting in the drivers seat it sounds like its coming from the front middle. The starter/generator motor is on the other side of the engine from where the sound appears to be coming. The sound seems vaguely in the direction of the gearbox.
Sounds vaguely like an abs pump in action, but there’s no feeling in the brake pedal.
What is it causing it?
It only happens occasionally. Has never happened below 45mph, when it happens its usually when braking with “medium” effort from around 60.
Braking lightly has never triggered it. Braking hard has never triggered it. Increasing or decreasing braking force when it does happen doesn’t stop it, but it will immediately go away on releasing the brakes or if the car has slowed to around 45mph.
There’s no feeling, not even a faint one in either the steering or the brake pedal.
These cars have a starter/generator motor with regen braking as part of their mild hybrid system. The belt drive for this hybrid motor looks brand new from above but its hard to get much view of the other side of the belt that actually drives against the pulleys. Car has around 200 miles on it.
The noise doesn’t change with steering input, it seems no more or less likely to happen regardless of braking in a straight line or with some steering input (tut tut, should be completing braking before beginning turning).
When sitting in the passenger seat, the noise sounds like it’s coming from the front left wheel. When sitting in the drivers seat it sounds like its coming from the front middle. The starter/generator motor is on the other side of the engine from where the sound appears to be coming. The sound seems vaguely in the direction of the gearbox.
Sounds vaguely like an abs pump in action, but there’s no feeling in the brake pedal.
What is it causing it?
It doesn’t happen as much anymore but I think we got to the bottom of it. It happened once when my wife was pulling up to park and I got a chance to hear it while standing outside the car - it came from the brake caliper / brake pad. It lasted long enough, in reality just a second or two, but was long enough to look where the sound was coming from and it was coming from the direction of the caliper assembly, not from the disc and not from inside the engine bay. So probably just the pad vibrating in the caliper sometimes but as the brakes have worn in it seems to have subsided.
Bit weird because I’ve heard squealing brakes before on other cars and I’ve felt brakes vibrating through the pedal because of deposits on the disc but this sounded totally different - louder and more like a nasty mechanical sound.
Bit weird because I’ve heard squealing brakes before on other cars and I’ve felt brakes vibrating through the pedal because of deposits on the disc but this sounded totally different - louder and more like a nasty mechanical sound.
RichB said:
I don't like the brakes on the XC40 at all. I find that there's very little brake feel through the pedal
They are s
t for feel, effective but zero feelRichB said:
occasionally, and unpredictably, when I apply moderate brake pressure it feels as if the car decided to press on
Definitely echo that - i'm used to it now but on the test drive it was the main thing i noticed and for the first few weeks of driving too.Gassing Station | Volvo & Polestar | Top of Page | What's New | My Stuff