High pitch squeal from n/s front, disappears under braking

[Kevlaar]

Hi all,

Recently purchased my W211 04 E Class, and it has just developed a "squealing" when driving between 0-25mph which disappears when braking.

I've done a little bit of research and a couple people have suggested that it could either be the retainer spring out of place and ever so slightly touching the brake disc. OR it could be that the pads deform slightly with heat and so could rub against any lip present on the disc.

I'm wondering if this is a common thing, and hoping it isn't wheel bearing related!

Any help?

Cheers!

 

[Reamer]

Are they worn out? I would take the pads out and inspect them. The sensor is only on one side so the pads on the adjacent side could be on the limit.


Sent from my iPhone using Tapatalk

 

[Kevlaar]

Are they worn out? I would take the pads out and inspect them. The sensor is only on one side so the pads on the adjacent side could be on the limit.

There appears to be PLENTY of life left in the outer pad and disc, admittedly I haven't checked the inner pad, so I suppose there could be a chance that the inner on is worn considerably more than the outer...which would be odd. Will check that when I get home tonight.

 

[Jonesy161]

High pitched scream!!! It's either someone stuck under the bonnet or anti squeal shims, defo not wheel bearing, that's a rumbling grumpy old git sound. IMHO.

 

[Kevlaar]

High pitched scream!!! It's either someone stuck under the bonnet or anti squeal shims, defo not wheel bearing, that's a rumbling grumpy old git sound. IMHO.

Checked under the bonnet, no-one there, going to replace the discs and pads soon and see if that helps. Maybe just the discs as all pads seem fine! Glad to hear that it's not the bearing though!

 

[PobodY]

Is it possible it's something as simple as an accumulation of dust/debris? - In which case spraying the pads and discs with some brake cleaner might make the noise go away.

If there's meat left on the pads check it's not something stuck in the grove down the middle (if there is a grove that is)?

 

[Kevlaar]

Is it possible it's something as simple as an accumulation of dust/debris? - In which case spraying the pads and discs with some brake cleaner might make the noise go away.

If there's meat left on the pads check it's not something stuck in the grove down the middle (if there is a grove that is)?

Will give it a shot, you're more than likely right. Will look tonight.

Only weird thing is the squealing started on the front left corner and now the right side is also doing it now. Maybe just coincidence.

 

[Kevlaar]

Update,

I decided to replace the discs and pads last night as there was a little bit of a lip on them anyway. The anti-squeal shims were quite worn although the pads looked nearly new, so I'm guessing that was the cause of the squealing, which has now gone.

New problem however is I'm getting a repeated knocking when breaking now. Sounds as if it knocks every rotation of the wheel as if something's loose/catching each time the wheel does a rotation. Will get under the car again tonight and investigate and check all the bolts are done up nice and tight.

 

[PobodY]

Check the hub nuts. - I had something similar on the Nissan, and it turned out to be the entire hub assembly shifting on the drive shaft; I discovered it when I went to replace the wheel bearings.

 

[Kevlaar]

Check the hub nuts. - I had something similar on the Nissan, and it turned out to be the entire hub assembly shifting on the drive shaft; I discovered it when I went to replace the wheel bearings.

You make a good point, I did have to hammer the hell out of the old discs to get them off, maybe it affected the hub nut? Will check it out tonight. Thanks!

 

[Mrhanky]

Worth checking for play and adjusting the nut to suit.

 

[Jonesy161]

This is a long shot but bear with me, check the surface of the new discs. If they are not perfectly smooth and there are signs of surface grooves from machining....like a vinyl record (told you to bear with me), the discs can "wind" the caliper towards the centre, then release, causing the knock.
After many years working on cars, I have only had two instances of this happening so it is rare but worth checking. Good luck.

 

[Kevlaar]

Thanks for the help guys!

So update, I stripped the brakes down again, tightened the hub nut (not that it was loose), cleaned down the hub, realigned the disc as it was slightly out of line, then tightened the hell out of the carrier and calipers bolts.

However the route cause of the problem I believe was me putting the pads in front to back...what a muppet. I'm sure that's what's caused the knocking.

Anyway, problems all sorted now, thanks for all the help everyone.

 

[RichardF]

How can you put the pads in "front to back" ? They only go in one way, and not "handed" surely?

 

[Kevlaar]

How can you put the pads in "front to back" ? They only go in one way, and not "handed" surely?

They sure can go on flipped front to back, I.e. Pad with sensor on the back of the caliper or the front. I had put the pad with the sensor on the frontside of the caliper.