Weird metal rattling noise when driving cold...

[metroplex]

engine: Ford 4.6L SOHC V8
car: 00 Crown Vic

When I first start the car in a rather cool morning (below 60F) and start to drive around the first 1-4 miles, every time I get on the throttle the engine makes weird metallic sounds.

When I drive the car during the day time (say, 9 hours+ in the parking lot, ambient is 60F+) the engine is very quiet.

Has anyone had this problem?

I try not to go WOT in the cold mornings just to let all the metal rotating parts expand properly or what not.

 

[chas3]

sounds like heat shields or heat riser.

 

[metroplex]

There's no heat riser for this car (00 Ford Crown Vic), and I checked the heat shields. They're solid.

 

[chas3]

can you localize the noise? mechanics stethescope or otherwise? and even though the heat shields seem solid they always find a way to rattle (or you find you didnt find all the heat shields).

any double-walled pipes in your exhaust system?

i once had a metal tag on a catalytic convertor break free inside the heat shields. it would only rattle when hot. i have had a riveted heat shield on an exhaust pipe only rattle when cold (it seemed riveted tightly by inspection)

 

[metroplex]

It could be the heat shields... I can hear a tapping/rattling sound when idling (even when the engine is hot).

I just hear a nastier ver of the rattling when I get on the throttle when everything is really cool/cold.

I'm hoping its not serious like a rattling heatshield, I'll have to look deeper.

 

[chas3]

get the car up on ramps/jack stands and listen through a cardboard tube (center from gift wrapping paper is a good choice). this should help localize the sound.

 

[boxcartommie22]

i have a 98 vic and on really cold temps <25 degrees or so i have this knocking sound which lasts for about 2 secs. or sosounds like its outside the engine somewhere when i listen with a stethascope i here it in the bottom of engine....don't know what it is..the rest of the year even when it sits for a couple of days it doesn't do it.. i use redline oils and baldwin filter..even when i use fl820s filters it does it..