catalytic converter

89 GT

Had a random rattle, found a weld on the driver's catalytic converter pre-heater heat shield was broken. Noticed that the heat shield has a nearly perfectly round hole in it, the size of maybe a dime, with rust another 1/8 around the hole. Something was sticking out of the hole and I started poking at it... it sounded like a leaf or something but it turned out to be some foil / tin along w/this crumbly / powdery substance pictured below.

I presume it's insulation of some sort...
if not, any idea what it is / what it's made of / what is it's function?

Also, are there any sensors / wires that plug into the pre-heaters?

General karthief said:

I think that is some road debris that got stuck in there, I never noticed and insulation around the cats on a fox era car, you didn't post what year your stang is.

Click to expand...

I poked around between the pre-heater and heat shield on the passenger side as well and, as far as I could tell without destroying it, the same "stuff" was in there...

it's at the top of the post - "89 GT"

AeroCoupe said:

There is a thermal barrier between the heat shield and converter on the stock converters. At least mine had it when I removed all the stock exhaust and tossed that crap in the metal dumpster 20 years ago.

Click to expand...

any idea what it is / made of?