Wierd... noises after engine's turned off
 

Guys, does anyone get periodical tapping noises from the car after you've driven it, and turned off the engine?

Anyone have any idea what it is? It seems to come from the middle of the car.

Thanks,
b0h

Re: Wierd... noises after engine's turned off
 

I get this too. I get this from all my cars. There's a great deal of heat generated from operating the car and all sorts of metal fittings, pipes, and gadgets under the vehicle heat up. When things get hot, they expand. When you turn the engine off, they start to cool again. The tinking/popping/clicking sounds you hear are just all your metal parts contracting again. Don't be concerned by this - it's perfectly normal and doesn't indicate anything is wrong.

Re: Wierd... noises after engine's turned off
 

The tapping or clicking sounds are due to the cooling of the very hot exhaust system. The heat shields cool at a different rate than the exhaust pipe and muffler. This is normal.

<font color=blue>Dan</font color=blue>

Re: Wierd... noises after engine's turned off
 

If you really want to know the material science behind it...The tinking noise is due to molecular dislocations moving thru the material at the speed of sound. The dislocations go from an area of high thermal stress to an area of lower stress...caused by differential coefficients of thermal expansion. The best analogy I can think of is imagine a zipper with one of the zipper teeth not engaged with its mate on the other side. When the tink happens the zipper magically rezips itself and the unengaged tooth moves to another location. Sorry, that was probably more than you wanted to know.

Re: Wierd... noises after engine's turned off
 

That's a great explanation - thanks for the clarification on what's *really* happening. That stuff is good to know. You some sort of physicist or something?

Re: Wierd... noises after engine's turned off
 

Mechanical Engineer