Does this rattling noise mean by cat is shot? (1 Viewer)

[GregMacd]

A couple of weeks after replacing the O2 sensors and an AFR valve on my 1995 LC (FJZ80), I noticed a rattling noise coming from the area near the front of the cat. It sounds like nuts and bolts rattling around in a tin can. The vehicle has 248k miles, and the cat was never replaced. (I attached a recording ). Any idea what this may be?

It only happens at idle when I'm not reving the engine, and pretty much goes away when I step on the gas. I can't see anything banging together or out of place when I look under the truck, so I'm assuming that it's inside the cat or muffler.

 

[bryson]

Are the heat shields loose on the cats? They often make a racket like that when they loosen up. That doesn't sound like an internal rattle to me. Check by banging on the cats with your fists (when they're cold of course...)

If they are loose, you can silence them by just crimping the edges with pliers, or using hose clamps around the pipe.

Another likely culprit is the bracket that clamps to the exhaust down pipe in the wheel well and bolts to the bellhousing/engine mating point. The clamps fail here often, and can just be replaced with worm-drive hose clamps. If the bracket is rusted or broken then obviously you'll need another bracket or a welder.

 

[Heckraiser]

My guess would be a loose heat shield.

 

[GregMacd]

Thanks! I'll check the heat shields during lunch by banging on them. If they are loose, do I crimp the edges with pliers in the clouded area on the attached photo? Would a hose clamp be installed in this same area?

 

[GregMacd]

Thanks! I'll check the heat shields during lunch by banging on them. If they are loose, do I crimp the edges with pliers in the clouded area on the attached photo? Would a hose clamp be installed in this same area?

 

[SUMMIT CRUISERS]

Hose clamps work on heat shields. I would determine if it's external to the cat by grabbing various areas with leather gloves, towels etc to try to locate/quiet the noise. If not external then the cat 's internals have broke apart and will need to be replaced. FYI you can sell the cat for at least 50 at a recycle/scrap business if you have to replace it.

 

[GregMacd]

Heat shields were the culprit! Thanks everyone for your help! Here's an after video (quieter now):