Strange sound
 

So i ve been in this forum for like 2 weeks, and man there are lots of knowledgeable people in here. This is my fourth 850 first manual, i ve had the car for over 3 years now, and since the first day i drove it, i noticed a little grinding after you first start the car and start accelerating. The grinding appears at around 19 - 20 mph, it appears only after starting the engine, you can drive for 10 days straight, without shutting the engine, the grind wont appear. The sound inside, sound like somebody 2-3 cars away from you, is pulling the emergency brake really fast. In the beginning i tried to investigate, because things like that bothers me a lot, but i had no luck, and since today, i hear it every time, i start the car, and start driving it always around 19-20 mph. Does anybody has a clue, or had that sound, i believe that it doesnt affect the car performance at all, just decided, to ask the many of experienced people here, just for the heck of it.

I don't understand your post. Maybe you can video and post the sound.

I believe I had the same sound you're describing before I rebuilt my turbo. Definetely post a video of the sound so we can help identify it.

I know exactly what you are talking about. This sound only happens at most once a day, because the car needs to be completely cold and sitting for a while before it happens. Mine happens at exactly the same speed too. It's a faint zipppp sound like he described that lasts maybe a second or less. I can't feel it in any way while driving the car, but I can hear it.

BTW, my car has ALWAYS made this sound. My transmission fluid was recently changed, and had no effect on the sound. My transmission is also in tip-top shape, with no signs of aging, wear, or malfunction. Going on 160K miles, and still working fine. I have dismissed the sound as something harmless.

Drive more, worry less.

Oh, I think I know the sound. At first I thought it was a suspension sound, now I call it a groan. I then thought it was the car coming out of "open loop" to "closed loop". It happens close to that time. I didn't notice it in my yellow sedan, or the S70, only this black wagon. Something is not right but neither am I. ;) Old cars, drive more worry less.