I have a 2001 Mazda b2500 manual with 185k. There is a sound that started probably close to a month or month and a half ago. It sounds like small rocks blowing around in the exhaust. It's coming from under the passenger side floor. I've tried to crawl under and locate it but it's too loud to find. It rattles anywhere from a few miles to over 10 minutes. It's not linked to rpm or speed and goes away if I shut the engine off even if I leave it in gear while rolling. I don't notice any difference in performance. Anyone have this problem or know what it is?

 

i wanna guess you catalytic converter is going or gonzo'd.

 

agreed ^^ Just buy a new exhaust and fix the problem.

 

A loose heat shield on the cat .
They are only tack welded on so with the vibration the weld breaks and lets them rattle.
Just make sure the engine has been off for a few hours before checking ,as they hold heat a long time.
I'm welding my inlaw's back on in his truck today.

 

yup. Mine does the same thing.

 

heat shield...old car had a loose one until it fell off going down the road lol

 

Thanks guys. I'll go check it once it stops raining and post results and maybe pics

 

Ya, mine makes heat shield noises every once in a while. Thought about pulling the ones off the truck since I think thats whats making noise on my truck.

 

so i checked the heat shield and it is actually rivited on my truck. I don't think it could make a sound this loud too. Inside the cab it's so loud I can't even hear the radio.

 

yeah they'll get pretty loud, does it sound like a can rolling or something?

 

Its more like rocks and sand in a shop vac. Maybe my cellphone will take a decent video so you can hear it.

I guess I'll just rip it off and see if it does any good.

 

So I took the heat shield off the cat and the one riveted to the underside of the cab. It's still making the noise. Now it only lasts a few seconds when I start it in the morning when it is really cold. Any ideas?