'01 S60: "scratching" noise under dashboard, then LOUD bang

[paul1149]

Thanks. I will do that. I didn't take it out today as I had planned, but I will tomorrow. Whatever it is, something forceful is involved.

[matthew1]

Been searching around, and am beginning to suspect the automatic tranny. 145k miles, have been having occasional minor slippage going into 3rd gear. That could explain the background "scratching" and somehow the loud boom, which would be ominous. Fluid has never been changed, and is filthy. No error code appeared.

Scratching on my car was the dust shield on the brake, its a flimsy backplate, I bent it with my hands so it no longer touched the brake disk.

This ^. A rhythmic (hey I spelled it right without autocorrect's help) scratching is a high probability of dust shield. Been there, done that. Or a hub going bad.

[paul1149]

Ok, I didn't get under the car, exactly, but I did take a decent look and saw nothing. Everything underneath looked tight. Up top, a power steering hose clamp needed wrenching, and I was surprised that the three bolts holding the top of the strut on the driver's side were not as tight as they should be. Not real loose, but not like they should be.

Just previous I had taken it out shopping. Mostly local roads, but on the way back I hit the highway for four miles, 65-70mph. The car was running very smoothly. There was no repeat of the noise until I passed someone. Then the scratching, which sounded more like rattling, began again, fairly subtly (there was a lot of read and wind noise to deal with). But it subsided, and I couldn't put my finger on it.

It has nothing to do with road surface, since the highway is smooth. I wasn't directly speed dependent, though there may be a minimum speed for it to kick in.

The transmission shifting is not as smooth as it was. I would say in the past year it went from an A- to a B- or even C+.

I don't know what to make of this. The rattling is one thing, but that big bang is quite worrying. It may be time for me to pick up another car just in case.

The belt is fine. I forgot to check if braking has an effect. And I will check the retaining bolts.

[scot850]

It could be a dragging brake. Do you use the parking brake at all? The cables can stick, and the rear parking brake shoes can delaminate causing rubbing noises and if the parking brake cable is sticking it could cause it to come loose with a bang.

Neil.

[paul1149]

I never use the parking brake. I used it once maybe a month ago to see if it's working - it was. I replaced the shoes a couple of years ago, along with all pads, rotors and rear calipers. Sounds can be tricky, but I'm quite certain that this was from the front of the car.

[jonesg]

loose strut, thats scary.

[paul1149]

Just a little update. The axle cap bolts looked fine. I've driven it a few times now, and no repeat, even of the scratching.

I took it to a mechanic and we drove it around "the block" - about 12 miles, half of it highway. I let him drive. Neither of us heard anything, and he felt nothing. We left it at that if it happens again, bring it right in for a closer look.

So I'm calmed down about this quite a bit. Nothing here means that it can't happen again and be serious. But the mechanic does also sell used cars, and he isn't far from me, so I wouldn't be stuck without a vehicle should something bad happen.

[jonesg]

I'd put money on that loose strut causing the bang.
Does it still track straight?

[paul1149]

Yes, tracking has been fine.