When my IS250 has been driving a while and everything is hot, from time to time when I put it in D or R and have all the music turned off, And i am holding the car stationary with the brakes, I can hear this strange rumble coming from the back of the car. Sounds like under the trunk. It's not an exhaust sound. Its very subtle and is impossible to record. It's just one of those annoying hums that if you know its there you can hear it.

As soon as I take it off gear and put on N or P, then it disappears. And also disappears if I come off the brakes and let the car move. Only happens when hot. Any ideas what this can be?

Thanks

 

Keep an eye on the dash. Sometimes (in my car) there is a little rumble when my car boggs down to about 500rpms when idling in drive but goes away when car is in neutral or park. Very rare occurrence but its also a sign that leads to the carbon buildup issue. I can hear it in my exhaust when it misfires a little bit its not bad to the point where i have to worry but its a sign.