So for the longest time I've had this annoying knock/rattle...aka noise...coming from what I was pretty sure was under my truck. However it really only does it when I just start the throttle, and usually only when in gear. I can put the car in gear and apply the break, and get it to do it sometimes, but not always. I was reluctant to have my helper (wife) get in the truck with the brake on and try and get under the truck to listen for the noise...that had Darwin Award/Front page headline written all over it.

So lately I've heard it a few times, ever so slightly, at idle when the truck was not in gear. I was afraid it was one of the valves or something, but my hunch was confirmed. It was under the truck.

I have tested the muffler in case it was loose because I had a Subaru that had a plate that had cracked on the muffler system and it made a similar noise. No dice.

Anyway, I am pretty sure it's coming from the catalytic converter, I tried to touch it to see if I could feel the vibration from the noise, but it was already too hot, but just moving my ear from the front to the back of the rig I'm pretty sure it's the catalytic converter.

Has anyone heard of those "knocking"? I need a new exhaust system, it's rusted out on the back and I've smelled fumes coming from the back if my back window is down. Now after reading about the catalytic converter I think that might be causing that problem too.

So I'm going to replace it, should I...

A. replace the entire exhaust system
B. just replace from that cat back, to save money (if this is possible)
C. just replace the cat for now

Either way I think I need a new cat, any suggestions recommendations? Is this something I should get OEM from Yota or can I get one at Napa/Ebay? Or do I go the full monty and get the Midas Touch?

Also, just because I'm curious as cancer now, what the hell is in them that makes people steal them? Someone told me there are "precious metals" inside, I am guessing for recycling, or are they just to sell for parts?

Thanks

Mike

 

Well, does your state have emissions? If it doesn't, I'd probably go without a catalytic converter. If it does, then you can buy all sorts of replacement cats from Summit Racing. Summit Racing is awesome! I've bought a few parts from them and they have been nothing but helpful.

I've never heard of a knocking from a catalytic converter. I've heard chugging come from them when they get close to being plugged, or I've heard them rattle like filling a coke can with marbles, but never a knock like an engine knock, if that's what you mean.

I'd probably replace the entire exhaust system. It's not too expensive and you can find good mufflers fairly cheap. I've even heard of people buying used mufflers from junkyards (find a late model muscle car, they usually have flowmasters, or similar on them) for around $40.

Catalytic converters contain precious metals in a mesh on a ceramic core. I'm not sure if there are more, but I was told three of them are palladium, rhodium, and platinum.

 

Thanks for the tip/advice. I would say it's more of a rattle than a knock, bad choice of words and it's why I used Rattle in the Cat as my subject.

It sounds like something is loose, a piece of thin metal, and it's rattleing against something solid, sort of a ping sound like a marble in a coke can I guess, nice choice.

I don't have emissions, but does the cat help the exhaust fumes that come in through the back window when it's open?

Mike

 

usually rattling from the cat (unless its the heatshield) is a sign that it's time for a new one. Go with a "high flow" one which should run you around $50-70. Replace whatevers rusted through on the exhaust. I'd atleast look at doing the cat + a catback setup.

 

Without sounding like a tool, what is a catback setup?

 

i had the same type of rattle earlier this year. It was the heatshield around the catalytic converter - a spot weld had broken. Pulled the heat shield off & no more rattle.


Vegascoug, a cat-back is just the rest of the exhaust system behind the catalytic converter (from the cat to the back).

 

When people refer to "cat back" they mean from the catalytic converter back towards the axle. So no exhaust manifold, or header, no pipe leading to the converter, just from the cat back.

 

Easy test just to put your mind totally at ease before spending the money.. get a rubber mallet (or even just your palm) and (when the trucks cold if you use your palm) smack the cat and listen for your rattle. if u hear it then its falling apart internally...

and if your state doesnt have emmisions i wouldnt run one.. butttt if the smell bothers you with the window down i would say the cat will help with that sumwhat

 

My friend suggested the same thing, since we don't have emissions tests here that skip it. I suppose I would need to get some straight pipe and have someone weld the flanges on, right? He said that no matter what that exhaust is going to come up through that window by basic design/air flow, etc. The cat might help a bit, but you'd still smell it.

I did that very thing yesterday, whacked it with my hand and I can hear a noise, it doesn't rattle like it does when it's running, but it does make the same ting/ping/noise when I hit it. But that only bumps it, I'm sure if I had the strength to move it back and forth as fast as it moves when the car is running it would make the noise.

Now to find a good welder, or is there a part I can buy already made?

Mike

 

Rattling Cat is generally one of the welds holding the heatsheild on have come loose or the ground heat sheild as well if it has both .
Most of the time the heat sheild will be thin metal spot welded to the corners at each end of Cat - years of Heat/Cold and Vibration make the metal break usually right on the weld leaving the weld .
If you have a buddy at the exhaust shop have him tack it for you or put a self tapping screw thru outside lip and secure it .
Thats of course is if that is what is causing it
If it is a heat sheild then much cheaper to fix than replace but if ya want a nice new one that is up to you and your wallet

 

check the heatshield on the cat before ripping anything out. These are known to come loose

if that's it, just rip the heatshield off or weld it back down, as you choose.

 

i know some of you yotatech heads have the magnaflow cat converter, reviews on it plz? is it worth it...

 

Just a quick note:
Check the O2 sensor. On my 91 3.0 4runner the mounting nuts rusted just enough to let it rattle/tap/knock like crazy but not fall out. It is mounted just before the cat on this model.
Remove nuts, run over studs with a die, replace. Problem solved.

 

We should refrain from saying Rattle in the Cat eh , what if an animal rights organization see that and realize's someone must be shaking the cat for it to rattle .....................right ...........OMG we better be careful .

Disclaimer :
No animals were hurt or used in solving the Rattling Cat Problem and futhermore the Forum does not and has not ever condoned the "Rattling Of Cat's" in any way , shape or form .

Thankyou
HEHEHE