Loud scraping sound on bumps at speed

[Romeo]

Hi, guys,
Mine is a MY2017 DS which has overall been pretty good since I bought it new. Lately I have noticed, when travelling at fair speed (above 90kph or so) and when encountering a sharp dip in the road (think ?whoosh?) I get a short very loud scraping sound, no obviously discernible metallic ringing element, just more like a (very badly) creaking rubber bush. Lasts for less than a second, not repeatable or predictable or consistent. Driving Adelaide to Melbourne 90- 110kph happens perhaps 20-30 times, more often on the 100kph single lane road than on the relatively smoother 110kph freeway. At first I thought wheel arch lining scraping the tyre (that sort of sound) but inspection showed nothing and it's really much louder and more assertive than wheel arch lining (which I did have once, corrected under warranty). Hard to pinpoint the direction - sometimes sounds like it's coming from the rear, other times from directly under passenger side, other times???. I recently had a local mechanic spend 1.5 hours inspecting the bottom of the car and re-inspecting the wheel arches for evidence of any scraping or rubbing around drive shafts, etc, without finding anything.

I never (well, only once!) hear it around town, so I'm reluctant to take it to LR dealer at this point.

Does anyone have any ideas or suggestions where to look/what to look for?
Roman

[oka374]

Engine mount gone soft or failed allowing rotating things like harmonic balancer to touch body part of cooling fan to touch the shroud? The latter not applicable to most late model vehicles as most have electric fans these days

[vnx205]

Years ago I heard a noise every time I went through a bit of a dip that caused the suspension to compress.
Because of when it happened and because it sounded exacty like a stick caught under the car scraping on the ground, I spent some time unsuccessfully looking for the stick.
I eventually discovered that it was a universal joint that had become very rusty; the result of driving through water some time before.
It only made a noise when the angle of the joint changed. On perfectly flat road it was silent.
Have you driven through water in the last year or so?

[Romeo]

Engine mount gone soft or failed allowing rotating things like harmonic balancer to touch body part of cooling fan to touch the shroud? The latter not applicable to most late model vehicles as most have electric fans these days

A soft engine mount was one of the things the mechanic who looked at it theorized about before he did his inspection. He said no more about it when I picked the car up with a 'didn't find anything?; I presume he looked there, but no explicit comment.
Thanks for the suggestion, though. It's on the list to recheck next time the car is up.
Roman

[Romeo]

Years ago I heard a noise every time I went through a bit of a dip that caused the suspension to compress.
Because of when it happened and because it sounded exacty like a stick caught under the car scraping on the ground, I spent some time unsuccessfully looking for the stick.
I eventually discovered that it was a universal joint that had become very rusty; the result of driving through water some time before.
It only made a noise when the angle of the joint changed. On perfectly flat road it was silent.
Have you driven through water in the last year or so?

Yes, a scraping stick (well, log, almost!) could well describe the sound. No, I haven't been into water hazards for quite some time, but that doesn't exclude the possibility you suggest. This will be on the list for a close inspection next chance I get.

Was the rust in your case visible? Which uni was it?

Roman

[vnx205]

It was the front universal joint on a 1969 Toyota Crown.
It was about almost 50 years ago, so I can't really remember how I found the cause of the problem. My best guess is that there were signs of powdered rust visible.