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Network Guy
Premium
join:2000-08-25
New York
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Time for new catalytic converter?

I had the muffler replaced in my Jeep sometime ago because it was rotting out and it sounded like it had an air leak. Ever since then, not only is the engine noise from the Jeep louder than my liking, but the air leak noise is worse.

Not only do I have the annoying air leak noise, but now it also sounds like metal rattle at idle, and normally once the engine is warm.

Quick google search tells me what I already think it is: catalytic converter.

I looked under the Jeep and saw what I'm pointing out with the green arrow in front of the muffler, just as shown in this picture (I borrowed this from the web but it looks just like mine). That to me doesn't look like a catalytic converter. So what is that? And more importantly, where is the catalytic converter?

The ones I'm seeing on eBay look nothing like what's in this picture.




shdesigns
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Stone Mountain, GA
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That is normally where the cat is. Look farther up the pipe to see if there is another can.

Try pounding on it with a rubber mallet or your fist.

The Jeeps are famous for mufflers breaking, usually the inlet or outlet pipe coming loose at the crimp to the muffler. When I had mine replaced, I had them add another hanger after the muffler to stop the twist load on it.

Check clearance, my CHerokee had all kinds of rattles after the muffler was replaced. There is not much side-side clearance and it often ratthes on the frame.

My Mustang had a cat go bad. Sounded like shaking a can of pennies at idle. The Cherokee also had one go bad, you could hear the insides sliding around after it was removed.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


Network Guy
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join:2000-08-25
New York
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Alright, I'll try that.

The rattling is intermittent. Never happens when cold, only when hot and after I've driven for a while and I'm sitting idle. I know this usually means a bad cat.



shdesigns
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reply to Network Guy

A note about having the cat replaced. The shop that did mine was relatively cheap. 6 months later the muffler fell down. Apparently they only slide the pipe in 1/2" and then put a clamp farther back.

That was not the bad part. When I needed to change the clutch, I found they had welded the new cat right to the downpipe flange rather than get a cat with the right flange. Made it real difficult to remove the downpipe and cat as one assembly rather than just unbolt it.

Find a good shop; that was the only thing I did not do after a rebuild and new suspension.

Might try getting it hot and then hitting with a 2x4.

Also, if you have had issues of the EGR valve diaphragm breaking (melting) you may have a plugged cat.

Has the cat been replaced before?
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


Network Guy
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join:2000-08-25
New York
kudos:2

No idea. I bought this Jeep back in January.

As far as I know, no issues with EGR valve. But I've yet to disassemble the throttle body in this truck, which is something I should do soon to clean it out.



shdesigns
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Stone Mountain, GA

What year Jeep?



VegasMan
Are We There Yet?
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join:2002-11-17
Schaumburg, IL
reply to Network Guy

You sure what you have pictured isn't one of those damn resonator cans?
Also the rattle could be a heat shield very common for rattling.
--
In need of a Vegas vacation.



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by VegasMan:

You sure what you have pictured isn't one of those damn resonator cans?
Also the rattle could be a heat shield very common for rattling.

This this this

- It looks like a resonator, it's too close to the muffler to be a cat. And there's no wire for the sensor.

- The rattling is most likely a heat shield. It happened to my car, in several spots. Damn thing. If your cat was finished, you'd feel a loss of power. I dont know if you'd even hear the rattling from inside the car. It could also be a loose U-bolt (Clamp) or many other loose things.

- The noise might be from an imperfect seal between the new muffler and the rest of the exhaust piping. A tiny little hole will make a lot of noise.

Start the car, squeeze under it (Take the necessary precautions) and try to narrow down the location of the noise. You'll probably find the exhaust noise at a connection between two pieces of pipe. If the rattling comes from the front of the car, open the hood and look at the very front of the engine where the exhaust manifold is located, there's a heat shield there as well. Mine was savagely rusted.


shdesigns
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said by alkizmo:

- It looks like a resonator, it's too close to the muffler to be a cat. And there's no wire for the sensor.

My jeep has no sensor at or after the cat. It is in the exhaust manifold. That is the exact location of my cat although it is a bit bigger (OEM was considerably bigger with a heat shield.)

That is why I asked if it was replaced, there are some real cheap ones that are tiny that don't last.
--
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Network Guy
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reply to shdesigns

said by shdesigns:

What year Jeep?

It's a 99 Laredo with 4.0L I6

Come think of it. I was looking for the O2 sensor but couldn't find it in that can. That's why I was confused as to where the cat actually is. I looked further up in the exhaust pipe but couldn't see it.

Network Guy
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reply to alkizmo

said by alkizmo:


- The rattling is most likely a heat shield. It happened to my car, in several spots. Damn thing. If your cat was finished, you'd feel a loss of power. I dont know if you'd even hear the rattling from inside the car. It could also be a loose U-bolt (Clamp) or many other loose things.

The truck definitely has plenty of power.

I can only hear the rattle if the windows are down. Definitely from outside.

Hmmm... You're now making me think I may not need a cat after all...


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by Network Guy:

Hmmm... You're now making me think I may not need a cat after all...

Well you should have a cat, but ya I doubt your cat needs to be replaced. Kind of like having a cough, it doesn't mean you have lung cancer

Network Guy
Premium
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New York
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LOL I meant that I may not need to purchase a replacement cat

I have some banging around to do under the truck. Hopefully I'll make the time this weekend.



Juggernaut
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Kelowna, BC
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reply to Network Guy

Check the heat shields. Those SOB's rattle bad when the welds break. Ripped a few off in my time...
--
Better to have it and not need it, then need it and not have it.


Network Guy
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1 recommendation

reply to Network Guy

Alright, so I went to a local muffler shop. I was waaaaaaay off on what this could be LOL

As VegasMan said, what I'm pointing at with the green arrow in the picture is indeed a resonator can. There are two catalytic converters... yes you read that right.. TWO.. waaay further up in the beginning of the exhaust pipe closer to the engine.

There was a section of the exhaust pipe between the two catalytic converters and the resonator can that was apparently patched up from when I bought this truck. The patch was starting to peel off. The guy welded the hole shut.

As for the rattle... There was a rusted pipe clamp that wasn't hooked up to anything right next to the resonator can. It was just sitting there loose. He pried it right off.

Thank God I thought to ask here and hit up the muffler shop first before buying anything. The total repair cost was $45.

The air leak is finally GONE. Haven't heard any rattle either, hopefully it stays that way. The truck finally sounds quiet. Good Lord amazing what difference that made!

You guys rock. Thanks again for the tips



Cho Baka
Premium,MVM
join:2000-11-23
there
kudos:2
reply to Network Guy

Sounds like your muffler shop rocks!
--
The talented hawk speaks French.



Tomek
Premium
join:2002-01-30
Valley Stream, NY
reply to Network Guy

In case of failing cat, shouldn't you get check engine light for that?
--
Semper Fi



Doctor Olds
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1970 442 W30
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said by Tomek:

In case of failing cat, shouldn't you get check engine light for that?

No, not always. For the onboard computer to determine converter status there must be upstream and downstream O/2 sensors and even then they can't see mechanical damage to the converters honeycomb matrix.
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time?


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
reply to Network Guy

said by Network Guy:

what I'm pointing at with the green arrow in the picture is indeed a resonator can.

heeeey I seconded him right away!

said by Network Guy:

As for the rattle... There was a rusted pipe clamp

That one I called first! HA! U-Bolt is a pipe clamp.

45$ is well worth the labor and trouble + pipe clamp (If they replaced it). Keep that garage in your cellphone's contact list. They are super honest. They could have claimed the resonator needed to be replaced, or charged you 2 hours of labor.

Bob4
Account deleted

join:2012-07-22
New Jersey
reply to Doctor Olds

If the check engine light if off and the car passes whatever emissions tests are required, who cares if the catalytic converter is failing?



VegasMan
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Schaumburg, IL
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1 recommendation

said by Bob4:

If the check engine light if off and the car passes whatever emissions tests are required, who cares if the catalytic converter is failing?

Well I guess we now know how the light got it's name.
--
In need of a Vegas vacation.

Network Guy
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reply to alkizmo

said by alkizmo:


That one I called first! HA! U-Bolt is a pipe clamp.

45$ is well worth the labor and trouble + pipe clamp (If they replaced it). Keep that garage in your cellphone's contact list. They are super honest. They could have claimed the resonator needed to be replaced, or charged you 2 hours of labor.

Yes, you did call it. Thanks for helping me out on this too

The clamp wasn't replaced, it was just pried off. That clamp didn't look like it belonged there. I didn't see it anywhere above the exhaust pipe where he could have installed a new U-Bolt.

My Dad went to this guy before to install a stabilizer bar in his Rav4. I happened to remember this guy did mufflers as well, so I went to him.