Exhaust ping?

[DeanMoriarty]

I noticed a pinging sound... sounds like bb's hitting a foil pan for a few minutes after shutting the truck off, coming from underneath from the exhaust. I figured this was just the exhaust or cat cooling... Then today when I was in a drive through (and had a wall for the sound to bounce off) I noticed it's making the same sound while the truck is running. Is this normal? It's an 01 Explorer btw.

 

[snake]

I think so. Mine really makes some noises when it is cooling off too, but I've never noticed it while the engine was running. When I shot the exhaust with a laser thermometer once, it was over 400 degrees...

 

[DeanMoriarty]

Hmmmm... I never would have noticed it if I hadn't been sitting parallel to a wall, once I pulled a few away I couldn't hear it anymore. The thing just passed emissions testing a couple days ago. Thanks for the reply, anyone else?

I dig the avatar btw, stewie is awesome.

 

[ForOffRoadDriving]

could be a seam leak on the muffler thats puffing exhaust on the heat shield and causing the noise?

 

[srteach]

The ping is normal when the truck is off. It is the cooling of the exhaust. While running, it could be due to rich exhaust, partially blocked cat / exhaust, or just heating/cooling of the exhaust.
It is usually not a problem unless you have drastically bad mpg numbers.

The exhaust should run between 350 and 450 degrees. Hot (about 500F) gasses from a controlled explosion are rushing through the pipe, why wouldn't it be hot?

 

[brendank]

Yes, it's just the exhaust contracting as it is cooling. Nothing to worry about.

 

[BeaterMan]

my 99 was doing that for a while and then reciently it got worse and the sound was only comming from the pass. exhaust header so i checked the bolt tightness and found that 2 bolts were broken off. put a new gasket w bolts on that header and no more noise except for the cats cooling off.