Rattle in Catalytic Converter 2003 Suburban

[Fitz98]

I have a concerning rattle/rapping noise coming from what appears to be the drivers side catalytic converter on my 2003 suburban 5.3L 1500LT.
It sounds like a rod rapping noise and only at cold startups. While moving and when the vehicle warms up, it goes away. It could be a harmonic vibration that starts the rattle on startup?
I jacked the truck up and got underneath, thinking I would hear the sound come from the oil pan, but sound seems to be from cat. If I hit the cat converter with a hammer, I can manipulate the sound (make it start or stop).
Has anyone experienced something like this?
Is there anything inside that can come loose and rattle against the exterior shell of the cat?

 

[maxdustington]

Heat shield?

 

[mattd]

.

 

[Fitz98]

Not the heat shield. It appears to be the cat itself, which is well isolated from the shield in this case.

 

[RonRonnster]

It can be common for the catalyst itself (honeycomb material) inside the cat to break down and rattle. Happened on both of the cats on my '98 Silverado across a couple year span. I ended up replacing both cats, but before I did so I took apart one of the cats and found the honeycomb rattling around inside.

It's possible for the welds on the heat shields to let go and starts rattling, but I've seen that happen more often on aftermarket cats, usually not the OEM ones.

How many miles on your rig? As far as you know, are they the original cats?

 

[clinebarger]

No heat shields on the catalytic converters, The heat shields are body mounted on GM trucks & has been that way forever! The catalyst substrate breaking free is not what I would call common.....But does happen!

 

[maxdustington]

Originally Posted by clinebarger
No heat shields on the catalytic converters, The heat shields are body mounted on GM trucks & has been that way forever! The catalyst substrate breaking free is not what I would call common.....But does happen!
They are mounted to the body on my car, too but we have this thing called rust in Canada.....

Didn't realize OP was in Florida.

 

[Warstud]

Time for a new Cat.

 

[GMguy84]

I have a '01 Suburban and had the EXACT same issue on mine for a LONG time, Drove me nuts


Turned out to be a bad pass side CAT


Was replaced with a better OEM style Magnaflow and all good no issues


Dave

 

[Dave9]

Originally Posted by clinebarger
No heat shields on the catalytic converters, The heat shields are body mounted on GM trucks & has been that way forever! The catalyst substrate breaking free is not what I would call common.....But does happen!


You might be overgeneralizing about "GM trucks". The heat shield on some vehicles is not shielding from the cabin, it is UNDER the cat to shield from brush fires, attached by welds or aftermarket or DIY could be straps. Granted if that was loose, you'd think he would notice it.

There are three concerns.

1) Do you have emissions testing and it failed?

2) Does the noise drive you crazy, enough to put money into it?

3) Are you a tree hugger that worries you are killing baby seals, trees, and algae on the moon?

Ultimately, it is a 2003 Suburban. If it has spent all its life in FL and away from salty ocean air, you shouldn't have much rust and then a failing cat is more often a sign of an engine problem causing it to overheat. If you do have rust as the cause, it may be time for more exhaust work than just the cat.

 

[spk2000]

Some exhaust system have a double walled pipe in areas for heat reduction / shielding purposes. If this has that sometimes the inside walls collapse. Also welds can burn through and the slag stick until some time later when they finally break free and destroy the converter.

 

[Fitz98]

Interesting you bring up the engine problem causing it to overheat. I have a check engine which is apparently a knock sensor, which I am told is a 500.00 repair since it is under intake?
Truck ran/runs fine, so I put it on hold, but wondering if it is possible that it is contributing to ruining the cat(s).

 

[nwjones18]

I'd say the cat is shot. The honeycomb inside them can disintegrate and cause them to rattle. Last one i had do that i just took it off and beat the rest of the guts out of it and reinstalled. Can't do this if you live in a place with emissions testing, or if you just don't like the idea of it.

 

[Chris142]

The honeycomb inside the shell has broken. Get it fixed now before it plugs up the exhaust.

 

[krismoriah72]

I also have a 2003 Suburban and have replaced both cats in the past year. Also replaced knock sensors.

Both of my cats threw codes and knock sensors as well.

My advice is Delco knock sensors. I had to have mine done twice due to first job being BWD sensors.

I would first take it to a muffler shop and test cats with heat guns.. you may have a lean condition melting the cats.

 

[Anduril]

Originally Posted by Fitz98
Interesting you bring up the engine problem causing it to overheat. I have a check engine which is apparently a knock sensor, which I am told is a 500.00 repair since it is under intake?
Truck ran/runs fine, so I put it on hold, but wondering if it is possible that it is contributing to ruining the cat(s).

Usually it's a misfire or running excessively rich or lean for a long period of time that causes damage. Burning oil too, but that plugs them, not burns them up. I had to drive my XTerra with a misfire for about 30 miles, got a P0430 right afterwards and when I replaced the cat, the honeycomb had melted from the unburnt fuel in the exhaust.

 

[Gasbuggy]

Ghetto fix is running a self tapping screw into it.