sound at start up/after engine is off

[Guest]

I'm having this strange sound on my 1999 Expedition XLT 5.4L. When i turn the engine off, there seems to be a crackling and popping sound when under the chasis. sounds like a knock when i start up cold...any ideas

 

[PaulC]

Any possiblity this is just from metal exhaust components contracting while cooling off? My X sounded like a pan of Jiffy Pop for years for this reason. Either it has stopped, or I'm so used to it now I don't hear it.

Catalytic converter heat shield loose?

 

[Guest]

My truck makes the same sound from the exhaust when it is shut off. It doesn't make the sound when you start it cold though. That sounds like the famous Ford piston slap. You may want to have that checked out.

Pat

 

[PaulC]

I didn't read your post carefully and missed the cold-start issue. Does the cold start noise vary with RPM?