Strange noise at idle.

[raup]

After driving home I'll park in my garage and I'll hear a faint ringing in the background. If I rev the car slightly it will become a little louder. I noticed that it happens when it's hotter out or if I drive the car hard on a cold night. If I drive normally it doesn't do it. The sound seems to be coming from the belt area or heat shield area. I've already done a search and I notice that other people have it while driving or when they first start their cars. I also made sure the sound wasn't coming from the heatshield, and it isn't. Mine seems to be only noticeable at idle. Maybe it's because I'm in my garage and the sound resonates a bit more.

After the car is cooled down I'll go and start the car and the sound is gone, even when I rev it a little (2k rpms). The only thing that I can tell at this point is that it's temperature (heat) related.

Any ideas what it could be? Thanks in advance.

 

[JDM Sam]

Try to get a video clip

 

[MSP#735]

Go Mazda!!!

 

[Spooled]

Check for loose bolts, especially on the heatshied above the exhaust manifold. Sometimes the washers "ring" on the thin metal.

 

[krillin]

when i think about it i notice the same thing on my car too. bleh, now i'm worried...

 

[raup]

Check for loose bolts, especially on the heatshied above the exhaust manifold. Sometimes the washers "ring" on the thin metal.

I've already checked the heatshield to make sure the bolts are tight. Let's say it is the washers. Why would it only happen after driving hard, or when it's driven on a hot day?

I'll see if I can get a clip of the sound using a digicam.

 

[mspdfreak]

Maybe because the heat expands the metal.

 

[raup]

Maybe because the heat expands the metal.

I've already checked to see if the heatshield is loose and it's not, thanks though.

 

[Dr.Sound]

i had 2 rattles.
one was exactly like described in the first post.

the other was the famous rattle between 1800 and 2000 rpm.
which i believe is caused by VCTS
i still have this rattle, but i was able to fix the first one.

it was caused by a bracket that holds oil lines to be loose.
it is the one that is above and to the right of the t-fitting that feeds the BPV.
it holds 2 lines and it is held by a bolt that screws in directly into the head.
in a few minutes i will go and take a picture of it.

 

[krillin]

pic?

i'm getting this weird sound too. i notice it after long drives or hot days. coming from the belt area. my friend said that it sounded like it was coming from the pulley's or something. ??? i shut the car off and let it cool for 3-5 min and it's gone.

i looked underneath and didn't really see anything loose. however, the pipe going from turbo to oil pan had drips of oil on one of the bolts at the turbo (diamond shaped with bolts on each end). i don't think it's related to the sound though.