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Catalytic converter replacement


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My wife has been complaining about the odor of my exhaust due to the hollow catcon. I have ordered a new unit on ebay and I recieved it this evening. All the parts are there gasket, hanger, clamp and converter - it looks great.

I am going over the replacement procedure and I am a little confused about how to remove the remainder of the old converter outlet pipe from the intermediate pipe after the converter pipe is cut. Has anyone done this before? I assume that I have to somehow cut along the axis of the pipe (lengthwise), but are the two pieces welded together.

I have a rotozip tool with a cut off wheel attachment and a hack saw. Are there any other tools that may come it handy for this task?



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What kind of odor? Rotten Eggs? If it is rotten eggs you may be getting a rich mixture, and the cat is ok... What makes you want to replace the CAT? Is it making noise? Pull the vacuum hose off the FPR and look for fuel.

It was not easy to remove mine, I bought one of those muffler pipe cutters and broke it, and finally used a hack saw. I had to have the rear of the CAT welded, as the rear of the cat did not meet up with the pipe well, they were more or less the exact same size. I think Midas did it for about $40

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As I said in my first post - the converter is hollow.

What kind of converter did you try to install? I believe mine is a model cc1188 direct fit catco converter. I measured the size of the outlet pipe on the new converter and the intermediate pipe it will attach to. The outlet pipe is slightly larger in diameter so it should slip over. The real question is how to remove the remains of the outlet pipe which is left on the intermediate after the old converter is cut.

If it is a press fit I will try to do it myself, if they are welded together I will save my time and let a shop take care of it.

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Oh I did not see that you said hollow cat, sorry, actually I didn't know what you meant... duh...

Mine was from Napa supposedly a direct replacement. But I think they intended for you to have it welded as in my case the pipes were too close in size. With that double wall you may have a hard time clamping down with a clamp... I know what you mean about the remains of the outlet pipe, its kind of doubled up at that location... that was another reason I got it welded... try to clean it up the best you can so that they meet nicely and get it welded, saved a lot of headaches for me...

Be very careful you don't cut it too short

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Hollow, smollo! We ran cars for all our lives before converters and they didn't stink. Suspect you have a bad diagnosis. How about those O2 sensors? A rich mixture in the modern engines stinks like he** converter or not. I used to have a Fiero that stank and didn't throw codes. It was fixed with a new O2 sensor.

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Thanks for the input Steve, but I am certain the cause of the smell is due to the cat. No smell before the hollow cat and smell after the cat was hollowed. The engine runs fine with good economy. I have a scanner that hooks to my laptop and I have monitored all the sensors - they work fine. The smell is not a rotten egg odor more of a chemical odor that can vary greatly depending on what gas is used. Regardless, I want the car legal again.

I plan on cutting into the exhaust tonight. I will try to snap some photos of the procedure.

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I once removed the converter from my '84 Cutlass. The smell was very distinctive. So much so that I was worried that a following patrolman might smell the car and pull me over. It smelled like a 2 cycle lawnmower. Almost sweet-smelling, but very distinctive. After a while, I put a new converter on it. Smell gone. :)

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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It took me 4 hours but I got it done. I had to run out and get new bolts to bolt up the converter to the header pipe since the holes on the new converter were a different size.

The converter is spot welded to the intermediate pipe in only a few areas. I was able to break off the remainder of the cat outlet pipe by using the cut off tool to cut through the outlet pipe lengthwise being careful not to damage the intermediate pipe underneath. With a mallet and prybar, I was able to crack some of the weld and peel the pipe off.

It went pretty smoothly but a small area of the intermediate pipe did come off with the outlet pipe. I temporarly patched this area with some aluminum and large hose clamps. I will get the pencil eraser sized hole properly patched ./ welded in the near future.

After bolting everything back up , I started the car - no smells. I have not taken it out for a test drive as it is late. This converter is smaller than the old one, I do not know if it will correct my smoking issue.

Here are some pics.


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Good job Maydog. I just saw this post, been away for a while. Would have pointed out my post when I changed mine out (a whole week before mine was totaled!) http://caddyinfo.ipbhost.com/index.php?sho...l=cat+converter

Mine was different though in that the old convertor slipped inside the intermediate pipe. I cut just behind the weld and slit the remaining old cat tail out with a dremel tool...

I'm sure you'll be happy with the results, and hope it cures your stinkin' problem! :P

'09 Cadillac CTS-4 3.6 direct injection, 128 K mi.
'15 Chevy Tahoe LTZ, 5.3i V8, 125 K mi
'70 Firebird Formula 400, Bored+.04, RAIII heads, M21 4spd., in-process restoration!

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MAYDOG.............Could be the fuel in your area too............

Certain additives are added in certain areas of the country during

certain times of the year.

Some for emissions, others for cold weather starting, detergents

and on and on..................

My GM fleet sometimes stinks like rotten eggs when running.

Even my old 8? Escort winter rat with NO cat !

Anyhoo............Get out the old johnson/pry bar/pipe and gut out

the old cat. (Ooopps.....I see yours is hollow)

Yup...........Its the gas then !......IMO

Thats what we do with our newer hotrods where a visual cat

inspection is required............................geo

93 DeVille-13 Chevy Impala

72 GTO - 77 Triumph Bonneville

84 Z-28

Syracuse NY

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Final update,

Everything is fine with the exhaust now. I had to tighten the clamps after a few days of driving but the smell is gone - best of all the smoking is history.

I wonder why this is? I have had 2 northstar engines smoke badly on deceleration when the converter was absent. No visible smoke is present with a converter in place. I think that maybe the converter hides the smoke by digesting / consuming - that would explain the oil usage mystery.

Is there anyone else out there running with a test pipe or hollow converter? What are you experiences with smoke?

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