I drive a 2003 Acura TL. This has been a great car, but there is one unexplained nuisance: It keeps making a humming sound while the engine is switched off.
Normally, it isn't a problem when the car is parked in the garage, but I can't take my car on camping trips because the humming sound keeps me awake at night!
Specifically, I hear a humming sounds that seems to come from the car's undercarriage. It seems to be louder outside the car than inside the car. The humming sound is at a nearly constant pitch; it sounds almost as if there is a person underneath my car humming very loudly.
Each hum lasts for several seconds and the hums are minutes apart, but I've noticed that they seem to go on indefinitely.
There appears to be no problem what-so-ever with driving the car; it just makes this strange sound over and over when it is parked.
What could be causing the problem and how can I fix it?
Update: I've been working on a timing belt change on this car. I've noticed that even with the battery disconnected, it still keeps making the sound!
Update: This question is getting old, but the car still has the same issue. Last weekend, I changed the front struts on my car. I drove it about 200 miles to where I raised it up to work on it. It was about 100 deg F outside and the car made that awful sound about once every two or three minutes (much more frequently than I remember in the past). Once again, I disconnected the battery and the noise continued just as before. It went on and on for hours.
Finally, I crawled under the car and found that the sound is coming from a grayish-blue plastic box with several electrical connections going into it. It is mounted about half-way between and slightly forward of the rear tires.
The next morning, I continued work after the car sat overnight and the sounds had stopped completely. I poured in a quart of motor flush, idled the engine for a few minutes, and changed the oil, and the sound was still stopped.
With that information, can anyone tell me what this odd plastic box is and why it's making loud humming sounds?