I hear rattling noise in my new Prius when changing from acceleration to coasting. Noise goes on for 2-3 sec?

Question

The noise is something like if you take a ruler, put it on a desk with half of it hanging over the edge of the desk, then press it tightly against the desk with one hand, and lightly bend the loose end with the other hand and let go.

Answer 1

There has been some discussions about sounds from the Prius over on http://www.priusonline.com/ , but I haven't been following the discussions as both of my Prius are acting/sounding normally.

You may also want to try some of the other Prius owners groups for suggestions:
http://autos.groups.yahoo.com/group/toyota-prius/
http://www.priuschat.com/

Best bet is to find another owner near you, and see if the sound is normal for the car or abnormal on your particular car. If your Prius is new, strange sounds should be covered under warranty, as long as your dealer's technicians are willing to go on a test drive with you to hear your sound.

Good luck!

Answer 2

The sound you are describing, in my experience at least, is most often caused by a loose or incorrectly aligned exhaust. I would tend to dismiss the incorrectly aligned exhaust issue as the car to too new for motor or transmission mounts to have failed which are the common causes of misalignment.

That being said, the most common source is a broken or missing exhaust mount. Scattered along the length of the exhaust system are a number of rubber hangers that suspend the exhaust system beneath the car. They are made of rubber to insulate the car from exhaust vibrations.

Now, when one or more of these hangers is broken or has fallen off the exhaust has a certain amount of play in it. When you let off the gas the engine, which is also on rubber mounts to isolate the car from vibration, shifts slightly and the result can be to tension off of the exhaust system, which is has a little play in it from the missing or broken hanger and that allow the exhaust system to vibrate, making a rattling sound a little like a baby rattle or a rattlesnake.

Answer 3

Very good description. You might have a bad catalytic converter. They can make a noise like you describe when the substrate material inside them goes bad. Almost any shop can easily tell you by raising the vehicle and banging on it to see if it rattles or if your comfortable doing so you can do this yourself by laying on the ground and simply shake it or bang on it and see if it rattles. But you said it is new? If it,s under warranty go to a dealer and let them take care of it.

Answer 4

I've had mine for nearly 2 years and I've never heard that sound. It could just be a piece of something loose from shipping, but it couldn't hurt to have them take a look at it.

Answer 5

Since the car is new you should take it to the dealer.