Intermittent grinding/crunching noises from rear (+ MP3 sound link)

Hi,

I have 01 bugeye and in the last year or so notice a horrible intermittent grinding/crunching noises (sounds like roughly cut aluminium blocks rubbing against each other) coming from rear left area. It's very annoying because it only happens some times (like it appears to happen while moving slowly down a mild gradient but not always). I brought it to carroll & roche (where i bought it) but of course it didn't happen during test drive around n7. Is it normal noise - it doesn't sound normal to me at all. How could I diagnose the problem? I had bearings go on an old Renault and it doesn't sound like that but could it be bearing/brakes/something else worn? Anyone experience something similar?

Here, sound speaks a thousand words so I recorded from inside the car using video camera and then extracted audio and saved as MP3:

http://rapidshare.com/files/413725459/WRX-grinding-noise-short.mp3

You can really hear it at around 1:25 when I start slowing down to traffic light.

Gaven

Re: Intermittent grinding/crunching noises from rear

Well its defo not a normal noise. But intermittant problems/noises are the most difficult to pin down. Unless you decide to systematically go through everything like brakes, suspension components and drive line components. When the noise is there, does it increase with speed? this will tell you if its driveline or brake related instead of suspension.

Its best to get a mechanic to put it up on a ramp and look for the obvious, then start looking at the less obvious. If something is rubbing then there will be signs of wear but these signs can be on the inside of components and not easily seen until its taken apart.

Have you changed the back pads recently or could it be a sticking piston in the caliper causing one pad to wear quicker than the other? Have the handbrake shoes been checked? I'd be looking in this area

Re: Intermittent grinding/crunching noises from rear

[quote author=Scoobymaniac link=topic=25882.msg304390#msg304390 date=1282139565]
When the noise is there, does it increase with speed? this will tell you if its driveline or brake related instead of suspension.

Have you changed the back pads recently or could it be a sticking piston in the caliper causing one pad to wear quicker than the other? Have the handbrake shoes been checked? I'd be looking in this area
[/quote]

I don't think it increases with speed (as the renault did with the bearing problem - i actaully thought that was a hole in the exhaust until mechanic pointed that out - noise got loader with speed indicating bearing and not exhaust hole). I'd say it might still be there but harder to hear and speed means it doesn't grind as much.

Haven't changed anything to do with drivetrain since bought it - could it be oil gone from rear drivetrain or something?
Haven't checked anything to do with brakes. I don't know enough about it.
I think there is some clue in the fact it gets really load when crawling along slowly in traffic jam when the car is facing down a slope of 10-20 degrees - like the sound of block of steel being dragged along the road.
I have a feeling its brake related too because sound changes when tapping brake to hold car on slope....

Re: Intermittent grinding/crunching noises from rear

Attached MP3 file to this thread...

I've listened to that MP3 several times man, but I can't make out anything with the exhaust and or road/wind noise. Its just a blur of white noise.

Next time you hear it slightly press the brake see if the noise goes away or gets worse, if it doesn't then slightly lift the hand brake and see if it goes away or gets worse.

Sorry I can't be more helpful.

[quote author=Scoobymaniac link=topic=25882.msg304461#msg304461 date=1282157671]
I've listened to that MP3 several times man, but I can't make out anything with the exhaust and or road/wind noise. Its just a blur of white noise.

Next time you hear it slightly press the brake see if the noise goes away or gets worse, if it doesn't then slightly lift the hand brake and see if it goes away or gets worse.

Sorry I can't be more helpful.
[/quote]

There is NO wind sound in the clip - the sound you think is wind from 1.25 to 2.04 is the GRINDING noise!

Yes the engine engine is loud but it fades at around 1.25 and the sound that takes over at that point (sort of like a buzzing/humming/wind noise/rumble that starts and stops repeatedly - it actually sounds like something from a sci-film film like independence day - it rumbles my laptop case) - that's the grinding noise. If you play it on laptop with crappy speakers it sounds like bee buzzing but with decent big surround speakers it sounds more like it does in reality... the sound stops at exactly 2.04 when car stops. That is not WIND noise - it's the grinding noise - see how much louder it is than even the engine!

could it be the rear suspenson mounting or spring not sitting right?