Clicking/crackling noise inside a 2004 Lexus Rx?

[ibex333]

2004 Lexus RX 330. Bought it with 117k miles on it, at 120k now.

Replaced timing belt just to be sure. changed the water pump. So far, so good... BUT...

When car is idling with engine on, I constantly hear this clicking/crackling noise. It's coming from under the car, and very audible inside. It's as if some kind of a relay it twitching off an on, or someone crumpling up a paper or hot coals cooling down... This sort of clicking/popping noises.

Sometimes, it goes away completely, but always comes back at a later time. I am definitely not "just hearing things". My father and my girlfriend both say this is clearly not normal and not ok, and they've both been driving much, much longer than me.

I didn't notice any weird smells and the car drives and runs like a champ.

What can this possibly be? I did take the car to a mechanic, but he just brushed me off and said car is fine. When a car is fine, there are no noises inside aside from the running engine! Yes, I know I should get a second opinion, but no time for that right now. Was wondering if anyone has any idea what something like this could be.

 

[homebrew2ny]

Honeycomb inside cadalytic converter going bad?

 

[jlee]

Does it happen immediately on a cold start? Does it happen on a hot start? Does it ever go away with time? Is it audible just at idle, or does it persist at higher rpm? If it persists, does the frequency, pitch, or any other characteristic of the sound change?

 

[mindless1]

Get under it and locate the source. Is it possible you're saying it's under the car but is just a relay box mounted near the floor or under a seat?

You could record the sound and post it on youtube/etc.

Hot coals cooling down suggests to me that you might just have a creaking exhaust. It has to expand and contract every time the vehicle warms up and cools down, along with possible heat shields attached to it and movement in the hanger brackets. If it has no leaks that wouldn't need fixed except to get rid of the noise.

Beyond locating the noise source yourself, you could also determine a specific set of circumstances that will cause the noise so you are better able to replicate it at a shop. If it needs to cool down first because it's happening as the vehicle warms up then you may have to drop it off there and schedule a time to go back and demonstrate it happening as it warms up.