WTF is that noise!

[JediBandit]

I have a 99 M5. All Stock, all original, etc. Lately I have started hearing what can best be described as a vibration at 3000 RPM and higher in first gear only. It goes away when I shift. I think I have it pinned down even further. It only seems to happen when the A/C is on max. But how in the world is something like noise out of my A/C unit connected to the RPM of my engine? I have 47K miles, so I am wondering if the belt is beginning to slip or something. But if that is it, why does it only do it in 1st gear. I am entertaining all ideas at this point. I don't care how silly you think it sounds. Thanks guys.


Chris

[L32Projekt]

Where does the vibration sound like it's coming from? Engine, tranny, driveshaft, left or right (offcenter)?

Jon

[JediBandit]

Sounds like it is coming from in front of me, too far forward to be the tranny, DS, or rear end. It is almost like it is coming out of the dash. It comes and goes, and I haven't heard it in a few days now.

I am going to replace my serpentine tomorrow, it needs it anyway, but it seems to have sorted itself out. I almost wonder if it wasn't just some loose change or something in the glovebox. I may have just been mishearing the direction of the noise.

I have been throwing SES codes sporadically, but when I got it read, it was an O2 sensor going out. The place reset the code, so the SES wouldn't bug me. The last time I heard the noise, the SES came on later that day, but shut itself off the next day while I was driving. I am waiting until the SES comes on and stays on before I do anything, b/c I want to get it read again to see if I am replacing the right part. I don't know. The first time the SES came on, it shut off when I turned into the parking lot of the place to get it checked. It came on again later, and that is when I found out about the O2 sensor. It is like my car knows when a mechanic is going to look at it, and behaves itself. I was going later that day to get the code read this most recent time when it shut off. Oh well, guess we'll see one day, huh?


Chris