Replacing Catalytic converter . . .
Replacing Catalytic converter . . . My passenger side cat has the rattles bad.
I found some direct fit replacements and want to do this my self.
Do I need bolts and gaskets?
I have basic tools and a battery powered impact gun tool (used it on the wheels)
Is it just the 4 bolts (2 on top & 2 on bottom)?
Should I be able to free them if they are rusted with my impact gun tool?
Anything else I need to know?
Shop wants $400, but I can get the cat for $250 shipped (with carb #) so I figured I might as well do it myself.
I found some direct fit replacements and want to do this my self.
Do I need bolts and gaskets?
I have basic tools and a battery powered impact gun tool (used it on the wheels)
Is it just the 4 bolts (2 on top & 2 on bottom)?
Should I be able to free them if they are rusted with my impact gun tool?
Anything else I need to know?
Shop wants $400, but I can get the cat for $250 shipped (with carb #) so I figured I might as well do it myself.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
The cat has 3 nuts on top (where it meets the exhaust manifold).
Spray the upper 3 nuts/studs with penetrating oil overnight.
Use a breaker bar to undo the upper nuts... the impact gun might break the studs.
If you break any of the 3 studs, you have to cut/drill them out, re-tap the holes in the manifold, and install new studs (they're cheap) with anti-seize applied.
Remove the rear O2 sensor before undoing any nuts/bolts otherwise the harness may stretch/tear when dropping the cat.
If you're going to re-use the gasket, make sure you place it back in the same orientation to avoid leaks, and if the gasket stays on the manifold, leave it there do not pry it off... but since it's a new cat, you may as well buy a new gasket.
So you live in CA and you got a cat DTC which won't let you pass smog...?
Spray the upper 3 nuts/studs with penetrating oil overnight.
Use a breaker bar to undo the upper nuts... the impact gun might break the studs.
If you break any of the 3 studs, you have to cut/drill them out, re-tap the holes in the manifold, and install new studs (they're cheap) with anti-seize applied.
Remove the rear O2 sensor before undoing any nuts/bolts otherwise the harness may stretch/tear when dropping the cat.
If you're going to re-use the gasket, make sure you place it back in the same orientation to avoid leaks, and if the gasket stays on the manifold, leave it there do not pry it off... but since it's a new cat, you may as well buy a new gasket.
So you live in CA and you got a cat DTC which won't let you pass smog...?
Clear on the dtc's, the darn thing just rattles, getting anoying.
Smog is 1 1/2 years away
Can I get the gaskets anywhere, like autozone etc . .?
Does the y-pipe need to be loosened to get the cat off from that part?
If so how hard is it to loosen the clamp on the y-pipe and exhaust?
Smog is 1 1/2 years away
Can I get the gaskets anywhere, like autozone etc . .?
Does the y-pipe need to be loosened to get the cat off from that part?
If so how hard is it to loosen the clamp on the y-pipe and exhaust?
Last edited by ls1tech.fan; Sep 23, 2010 at 12:40 PM.
Where do you live? If you can get away with it, I'd just remove both cats and then get a tune with the money you save by not having to buy a new cat. Your cats will never go bad again then since you won't have any.
TECH Resident
Joined: Jan 2003
Posts: 937
Likes: 0
From: South Alabama
You don't say what year car you have, if its an 01 or 02 (perhaps 00 as well-cant remember) GM increased the cat warranty to 10 years and / or 120 K miles.
They will replace it free under these conditions.
They will replace it free under these conditions.
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Verdad Gallardo TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
Are you sure it's the cat rattling...
I found my rattle to be the i-pipe slip joint had gotten loose even tho that clamp was all tight...
I fixed it by applying a pipe expander to the front pipe so it fit snug inside the rear pipe.
With new cats and new front O2's you should pass smog very easily when the time comes.
I found my rattle to be the i-pipe slip joint had gotten loose even tho that clamp was all tight...
I fixed it by applying a pipe expander to the front pipe so it fit snug inside the rear pipe.
With new cats and new front O2's you should pass smog very easily when the time comes.
Had a shop confirm it and its plain as day when one gets down next to it, getting worse the more I drive, first a bad rattle now sounds like more loose parts rolling in there . . . won't be suprised if I backfire some broken particles . . . and it guts itself . ..
Last edited by ls1tech.fan; Sep 24, 2010 at 12:12 PM.
You won't have to drop Y pipe, it's a flange joint from Y to the cats. Lot's of break away, and a BIG breaker bar. I just took all this stuff off last week for LT's. Get that thing outta there before it clogs up your perfectly good muffler or starts making the muffler rattle.
I've got this same problem, horrific rattling sound coming from the cat, plus I've got the SES light.
I could take it to a dealer to have it replaced under warranty, but I've got a cutout and a catback, wouldn't that void the warranty?
I could take it to a dealer to have it replaced under warranty, but I've got a cutout and a catback, wouldn't that void the warranty?
They'd have to prove those parts took out the cat.
However, I did read one thread about warranty being denied because the cat had a dent in it. So check yours out before you go.
Be VERY careful not to break the studs! between the two sides I broke three of them getting them out. Of course, I was just junking the manifolds for a ehader swap so I really didn't care/take much caution.
Thanks, I did a pre run and loosened everything no problem (then tightened them back up) wanted to be sure nothing was rusted tight.
Just got my car back from Royal Chevrolet (excellent GM dealer if you're in the Richmond area), they replaced BOTH cats even though only one was bad, all under warranty at no charge to me, even offered me a loaner car for the day. Didn't mention the catback or the cutout once.
Who says that all GM dealers suck?
Who says that all GM dealers suck?
