Hello, guys
How's the weather there?

My drive is lovely blue 07 S40 on 80000miles.

When I cold start the car and reverse it,(5 days in garage)

I hear strange low-pitch whining noise from right side.
Probably from one of the wheels since it happens on every rotation.
Though it's not constant, this is what you hear when you brake 80%.
Can you imagine? The sound is : "Woooo.......Wooooo.........Woooo."


After rolling up for one minute, it goes off.
Once it goes off it never happens again low or high speed whatsoever.
It feels like it gets louder when I turn the steering, though I'm not 100% sure.

I don't think it's brake pad, the pitch is too low.
Anyone had similar experience?


p.s.
I start to notice, on cold start auto recirculation system open-closes 10 times in 10 seconds. I don't know if it happened before. Is it normal?

 

My guess is it is the brake pad/rotor just cleaning itself. Do you set the parking brake regularly? I'd try a simple self test of jacking up the car when cold and give the rear wheels a hand spin to feel if there's anything.

 

Yes, I use it a lot. Every Park, every red-light. I didn't know they had self cleaning algorithm. :P I'll try it out. Thanks!

 

the self cleaning algorithm is simply the fact that the brake pads float on the rotors so any surface oxidation gets scrubbed off when you drive the car and lightly touch the brakes during your normal back up, turn around etc. when you park, the areas under the pads don't get exposed to any moisture - thus there's a strip of clean that makes a slightly different sound when rotating. Its actually a good idea that you use the parking brake regularly as that action keeps the cables and the mechanisms free.

 

Interesting fact. Isn't applying parking brake puts load?

 

I'm thinking it's the electric power steering pump. It's in the right front corner and down a little bit, under the coolant reservoir. Works when you turn the wheels. Maybe?