This is my first post, so my apologies if this issue has been brought up in the past...

So I was driving home last night and all of a sudden it sounds as though I am dragging something. It sounded as though my exhaust fell.. So I pulled over, popped my head under the car and nothing. Nothing hanging off, anywhere. I figured, ok, so I hit debris lying in the road, dragged it for a bit and it was gone. Cool. So I got back into the car.. hit the gas and there is it again. Now this is what I observed, or heard:

1) only happens when hit the gas and accelerate. When I take my foot off the pedal, it comes to a stop. Coast - nothing.. Pedal - the noise starts.

2) It sounds like someone is shaking a can with some small rocks in it.

3) Performance is fine. Other than that ghastly rattling, the engine actually runs nice. As strange as that sounds. (no pun intended)

4) Temp guage reads fine, nothing over-heating. Oddly, everything seems ok there too.

5) noise seems to be coming from the front of the car..

6) This could be just me, but it seems when I am going down hill, there is no noise, even when hitting the pedal. Strange.. Again, that could be me.

7) I assume it is nothing with the wheels, as the noise would be contant.

I reached under and the heat shields seem to be secure, but that is only what I can reach, and I know there are shields around the cat, the O2 sensor and along the exhaust system, so there is likely more I couldn't get to - I can't squeeze under the car like I used to be able to.... LOL

Anyway, that is the optimistic side of me.. Hoping it is not a drive train issue, or anything crazy, truth be told, I just don't have the $$$ to do that.. Unfortunately the old gal would have to be put out to pasture.

Any insight would be wonderful... Realizing a trip to the mechanic is probably a good idea at some point.. But we like to self-diagnose, eh? LOL

Thanks in advance.

Just realized I never said anything about the car.. 1995 4dr Volvo 940 Turbo.. 168k miles. Sorry about that. Might be helpful.

 

there' a center bearing on the drive shaft, just forward of the middle U joint. Its held in a rubber donut, which is in a metal bracket. this is a frequent wear item, and can make all sorts of awful sounds... the donut goes first usually but I've seen frozen bearings, too.

but, you also could be describing 'piston slap'. or predetonation aka pinging aka knocking. turbos are particularlly prone to these. piston slap pretty much means drive it til it dies and find another motor. predetonation should be fixed ASAP, and is usually caused by tuneup sort of issues, bad gas, etc.

 

Best to put the car on a a lift and examine the driveline, and if per chance you caught some debris. At any rate, I doubt it's serious... The drive shaft possibilities are not expensive. As the sound is present only under load, that's the place to start. Or put a couple of persons in the back seat and see if it gets worse.

 

Sounds to me like heat shield rattle. There are several heat shields on the original downpipe running from the exhaust header to the catalytic convertor. Take a peek under the car and examine the exhaust pipe in in front of the cat and see if there are remnents of heat shields. If there are, see if they are loose and rattle on the pipe. Make sure the engine is cold when you do this. Don't want any burnt fingers.

 

So things got a bit more interesting for the better I assume, of course ignorance is bliss, right?

I left work yesterday and drove home and not a sound. Made another trip this morning and again no sign of the sound.

I recall just prior to getting to work yesterday, I drove over some road construction, over little rocks etc.. Maybe if there was something rattling around in there, those rocks knocked it loose?

Of if it was one of the shields, it broke or fell off?

Car seems to be running fine, again no temp issues, idle issues, acceleration issues, nothing.

My neighbor joked and said maybe it was a squirrel. Pretty noisy bugger.

Anyway, I will continue to monitor it!

Thanks to everyone for taking the time to offer advice. With the recent hurricane, funds are really low, so a large car repair would not be a good thing for us now.

 

fwiw, heat shield noise tends to be really tinny sounding.

 

I had a scraping noise under acceleration. turned out the fan on the alternator damper (pulley) was scraping on the adjustment black fastening nut. A combination of shot bushings and gorilla over tightening belts.

 

Since I mentioned the sound up and stopped a short while back, still no sound, and the car seems to be running fine.

For now, I guess I can chalk it up to some debris fallling off, something like the shield falling or breaking off, or my worsening deafness. haha

That said, I am getting it inspected this weekend, so I will report back with whatever news I get! Hopefully, nada.

Thanks to all!

 

I also have a problem with a metal on metal scraping noise. If the car has been setting for a 10+ hours: I start it up and slowly accelerate the scraping starts. I can also hear a noise like scraping with tire rotation. After driving 5 minutes the sound will stop, but if I roll down the windows I can faintly hear a scraping noise with the tire rotation. I took it in to dealership, they found nothing wrong. Break pads are okay. Should I take it in again???

 

BTW, it's a 2008 s40.

 

an S40 is a front wheel drive car based on, I believe, a Mitsubishi or Mazda or something, that has NO relation or parts commonality with the RWD 240/740/940's we discuss on this forum section....