Noise from rear wheel / drive train

P

PeterF

Member
I'm posting this in brakes section, although the issue may well be in hub, drive shaft or diff area.

A noise is emanating from the rear offside which is a scraping sound at walking pace but becomes a squeaking at normal road speed. The noise has a frequency which increases with road speed. The noise disappears when lifting off the throttle or braking. It also disappears after a few miles of driving, presumably when the offending component has warmed up.

Jacking up the rear wheels and putting in drive to spin them does not generate the noise. Turning the hub by hand doesn't produce the noise but there is a slight soft scraping sound which I think is caused by the brake pads rubbing against the disc when turned. There's no noticeable play in the hub bearing.

I suspect the rear disc brake is the culprit. But before I start stripping down has anyone got any thoughts on what this could be?

Thanks in advance

Peter
 
Hi Peter,

It could be one of the pads from the near-side brake. If the material has all but gone contact between the disk and the backing plate will do as you describe. If inspection shows this not to be the case, either one or more half-shaft universal joints could be in need of replacement, or the hub bearing itself. The hub bearings don't usually exhibit play when they have started to fail. The bearings typically suffer from pitting, so if anything they become much harder to turn by hand. You would need to release the half-shaft from the disc to allow for a more thorough diagnosis and then finally remove the hub from the elbow and withdraw complete with half-shaft attached.

Let's know what you find.

Ron
 
Thanks Ron.

As you say, could be a few things really. The pads have been replaced not so many miles ago, but I'll check their condition.
I think I'll get my wife to drive the car backwards and forwards over the pit while I'm underneath so I can try and pinpoint where the noise is coming from. Not so easy I know, as noise travel easily through metal, but worth a try.

Peter
 
I got the car over the pit and checked the condition of brake pads on both sides. All were good with plenty of meat left, as I expected. Also got my wife to drive backwards and forwards whilst I was underneath listening for where the noise comes from. No joy, it was probably too low speed and I didn't hear much at all.
Doing a road run I can eliminate the noise when applying either foot brake or handbrake, so it points to the interference fit between the pads and the discs. Hopefully not a big issue and maybe it will go over time as the pads wear down.
Unless anyone has other theories!?
 
quattro said:
I was thinking more about CO poisoning TBH :)
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Fair point. I had front and rear doors open and a good through draught; plus it was only for a couple of minutes. CO will sit in the pit though, so don't leave the car idling for ages whilst underneath!
 
If you have fitted new rear pads recently to old discs then the cause will be a rust band on the disc rubbing on the new pad. This is consistent with the noise disappearing when the brake is applied, and also disappearing after a while as the pad and piston in the caliper get knocked back by the rust ring.
 
cobraboy said:
If you have fitted new rear pads recently to old discs then the cause will be a rust band on the disc rubbing on the new pad. This is consistent with the noise disappearing when the brake is applied, and also disappearing after a while as the pad and piston in the caliper get knocked back by the rust ring.
Click to expand...
That's a logical possibility. I checked my records and in fact the pads were replaced about 1000 miles ago. I can't remember when the noise started - it's been a fair few miles and might have coincided with the pads replacement. I think I'll leave it for a while and see if it quietens down.
 
Have a look at the discs, if there is a significant rust ring(s), support the car safely and run the drive train whilst sanding the discs with some 80 grit paper to get rid of the crap.
The correct way to do brakes is new discs with new pads, but who does that ?
 
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