High pitch winning at low speed

[Capra]

My car and me made it to 100k. Never thought I would see my C350 to this. Only recent issue was a DPF pressure sensor.

Anyhow. As a gift to me, my car thought now would be a good time to start a very high pitch squeal at low speeds, at around 20-30 mph. I think it's coming from the rear.

I'm thinking bearings of some kind??

 

[KennyN]

Not much to go on there fella , a bit more info would be nice.

I high pitched squeal from a bearing normally appears with high speed rotation , more of a rumbling at lower speed.

Does it go away when the brakes are pressed , slightly ?

Could it be the fuel pump or tank breather ?

Is it RPM dependent ?

Is it gear dependent ?

Does the vehicle have rear air suspension ?

K

 

[Capra]

Yeah, I knew it was vague. Let me have another look tomorrow. I can then run in M mode and select gears.

No, there is no air suspension.

 

[Dean Fletcher]

Common squeals, wheel bearing or rear parking brake springs corrode.
I had to sort both on my 130k E250

 

[Capra]

when this happens, if I slightly push the brake with the left foot the sound stops.

 

[Dean Fletcher]

when this happens, if I slightly push the brake with the left foot the sound stops.

Is this the foot brake or the pedal?

 

[Capra]

Pedal, I suppose two different mechanisms?

 

[Capra]

If I press the brake pedal it seems to stop it, pushing on the foot brake, makes no difference. Are the rear parking brake springs simple to check, I have trolly jack and stands.

 

[Wighty]

If I press the brake pedal it seems to stop it, pushing on the foot brake, makes no difference. Are the rear parking brake springs simple to check, I have trolly jack and stands.

Rear parking brake springs are inside the rear brake discs hub , so you would have to remove all the rear calipers and discs ,
Jack the back of the car up and you can then spin the rear wheels to try and pin down the sound ?

 

[Dean Fletcher]

they will make a rattling grinding noise when they go.

 

[ALFAitalia]

Rear parking brake springs are inside the rear brake discs hub , so you would have to remove all the rear calipers and discs ,
Jack the back of the car up and you can then spin the rear wheels to try and pin down the sound ?

But you can see from behind the wheel if the springs tails have pulled through the rusty backing plate....as they had on our A Class.

 

[Wighty]

If I press the brake pedal it seems to stop it, pushing on the foot brake, makes no difference. Are the rear parking brake springs simple to check, I have trolly jack and stands.

Any update buddy ?

 

[Capra]

Hi all. I've ignored the problem, but today I've made a decision to have a look.

I've just posted on another thread about jacking points and axle stands, basically I'm not sure where to jack and be able to use the stands for safety.

 

[Capra]

Rear parking brake springs are inside the rear brake discs hub , so you would have to remove all the rear calipers and discs ,
Jack the back of the car up and you can then spin the rear wheels to try and pin down the sound ?

Is this really a job for the garage, I am very good at undoing nuts etc, but.....

 

[w204benz]

Is this really a job for the garage, I am very good at undoing nuts etc, but.....

Perhaps look for a few youtube videos on servicing drum brakes? Effectively the same as the parking brake from my understanding, and you'll have some idea what is involved.

Personally, I don't want to mess with springs under tension - so I leave it up to my mechanic!

 

[Dean Fletcher]

Is this really a job for the garage, I am very good at undoing nuts etc, but.....

im no mechanic and managed to do mine without any issues. take photo before you start and invest in some long pliers

 

[Wighty]

Is this really a job for the garage, I am very good at undoing nuts etc, but.....

The thread seems to be drifting a bit , you say you have a squeal from somewhere at the rear . Why don’t you ask a tyre shop to jack the rear off the ground, spin the rear wheels and see if you can pin the sound to one side first (£10?) .

 

[rich.g.williams]

If I press the brake pedal it seems to stop it, pushing on the foot brake, makes no difference.

Herein lies the problem, we don't know which pedal stops the squealing, clarity is needed please:-

a) Foot brake and brake pedal are the same to me - the main brake that stops the car with disk pads on every wheel

b) Parking brake foot pedal - the parking brake that is used for parking and clamps the rear wheels - its not used during driving only for parking.

I'm guessing you are saying if you gently press the brake pedal (the main brake that stops the car with disks on each wheel) with your left foot as you are driving along the squealing stops yes?

If so its probably the disk pads leaning on the disks and is most likely coming from the front pads.

 

[Capra]

Turns out the garage was correct, they were advising changing the front pads and discs. Since doing this the problem has now gone....at last!