Today I come up to stop light and I hear rattle under my car that is not normal. I take off and I don't hear it - I slow down and I hear it again. I put the car in park and rev the engine and it comes back. I have someone look under car while I rev motor and sound seems to be coming from the inside of the right side (passenger side) of the HFC. It sounds like there is a bolt inside the canister rattling around.

I did a quick search and did not see anything on this topic - I'm suppose to head out of town tomorrow, but a little concerned about that this is. Anyone have experience with this?

Thanks!

 

Well I don't have Stillen or aftermarket HFCs, but both of my stock converters rattled in this manner and it turned out the catalyst honeycomb inside broke free from the metal body of the converter. It was moving around and making the rattle.

 

@AdamWest - thanks....I talked to the guys at Stillen and they basically said the same as you. Sound went away today, but long story short they are on their way out and I need to find replacements.

 

it could be the driver side heatshield as well

I get a buzz with art pipes

 

it's on the passenger side -

 

RWD or AWD? I has a similar noise but it was a bolt lodged in between the forward driveshaft and the trans housing.

I would also jack it up and check all the heat shields before pulling the cat.

 

Vid of the noise, I just went through this an my passanger side cat was shot, Replaced it under warranty, Mine actually sounded like rod knock. :/

 

Usually heat shields have a different rattling sound which is much lighter because the metal is thin. The bad cats sound like marbles rattling around inside a can, usually a deeper sound to it.

 

How many miles on those Stillens?

 

Get under the car and check the heat shields. If they're tight then it's most likely the cats.

Question, do the cats loose their functionality when the cat material becomes loose or is that merely an annoying occurrence. Could they be fixed?