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Primary Cat Removal: Defeated by a shield bolt.. lol!


microfiz
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So I own a 2001 LE (3.5 L). Last week, I heard a loud rattle emanating from the driver's side. I took a quick peek and found the second half of the primary cat was loose). Ordered a Cal-approved cat from Rock Auto and proceeded to remove everything yesterday. It looked like I needed to remove the heat shields (two) for the cat to gain access to the exhaust bolts (6). There were also 6 heat shield bolts that I needed to remove, and I got 5 out except for 1 (at the bottom, and presumably more affected by moisture). I think I may have even stripped the head off after spending 3 hours on it.

 

Anyway, this is a multi-tiered question:

1) since the car is not throwing codes, the single row of ceramic seems to be doing an adequate job scrubbing the exhaust. Should I just forget about replacing since the car is running good? With all the loose pieces removed, she's been quiet as can be.

2) is there another way I can gain more access to that bottom exhaust bolt so I can use other tools OR even grind it out? Can putting a jack on the engine help?

3) how about removing the manifold outright (driver's side)? Is that hard?

 

Thanks any advice in advance. =)

Edited by microfiz
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I just want to confirm it is definitely the cats and not the resonators causing the problem? Contrary to popular belief, R50’s only have one set of cats, which are tucked up closer to the manifolds. They should look like this.

2ad2a89e2caee3c065704b41848bc873.jpg

The other things further down that look like another pair of cats are only resonators, but many shops and even parts catalogs will mistake them for cats. The resonators are notorious for falling apart and leaking/rattling.

 

Even if it is the actual cats, if there’s no more noise and no CEL then I’d say don’t worry about it until it becomes a problem.

 

 

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I assumed those are what he's talking...

 

If it's just one bolt keeping the heat sheild on. Do what i did and bend that sob out of the way to get your access to the actual bolts to remove the part.

 

Of the catalyst is already breaking down it will just continue to do so. Might as well replace it

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Thanks for the initial feedback, guys.

 

Bax03SE... Unfortunately, I live in California and I am almost certain that the "resonators" (unit past the post-catalytic O2 sensor) also serves as a catalytic unit (it does have the honeycomb ceramic construction inside AND has the CARB embossed on the heat shield). But that's not the one rattling... it's the one you have attached as a picture. And the first half of the ceramic is intact.

 

Remus92, was your stubborn bolt the one on the underside too? And I assume that bending the shield out of the way was relatively easy?

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Ahhh, I didnt realize CA was different, although it makes sense. I removed the resonators on mine because they were leaking along the seems, and mine were definitely straight through inside with no honeycomb material or anything.

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Contrary to popular belief, R50’s only have one set of cats, which are tucked up closer to the manifolds.

 

That would be nice, but there actually four cats, two per bank. It's kind of weird how Nissan shows them in the FSM, because they don't show all four in the Fuel and Exhaust chapters, which only shows the rears. The fronts are shown in the Engine Mechanical section. They'll be listed as "TWC" for three-way catalyst.

 

Ron, lifting the engine might not give much clearance, except maybe if you loosen the two bolts at bottom of the motor mount. Might only create extra work, though.

 

Normally I'd say if you've come this far, go the distance and swap it out (otherwise it'll come back and haunt you!), but for stuff like this that doesn't seem to trigger a code, and for an expensive part like a cat, I'd probably forego the work and return the unit. If the issue, or another related issue, manifests, you'll be back under there anyway.

 

Though, one other option might be to warm up the exhaust first (careful working around it), or soak it in penetrating oil and see what additional leverage you can get on the bolt. Perhaps vice grips and a small cheater bar would come in handy. I think your local parts store may also have a loaner set of bolt extractors.

 

One other reminder is to look for local catalytic converter recyclers if you do replace yours. There are even online scrappers. It can recoup a decent chunk of the costs of a new unit, though I don't think the pre-cats (show in this post) are worth as much as the rear units.

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Ron, lifting the engine might not give much clearance, except maybe if you loosen the two bolts at bottom of the motor mount. Might only create extra work, though.

 

Normally I'd say if you've come this far, go the distance and swap it out (otherwise it'll come back and haunt you!), but for stuff like this that doesn't seem to trigger a code, and for an expensive part like a cat, I'd probably forego the work and return the unit. If the issue, or another related issue, manifests, you'll be back under there anyway.

 

 

One other reminder is to look for local catalytic converter recyclers if you do replace yours. There are even online scrappers. It can recoup a decent chunk of the costs of a new unit, though I don't think the pre-cats (show in this post) are worth as much as the rear units.

 

Patrick, I'm almost inclined to just return the cat but as stubborn as I am, I will probably do one more attempt at it. Frankly, removing the secondary cat was a breeze, and after I gave up yesterday, it didn't take more than 30 minutes to button everything back up (I even applied anti-seize on the threads). The seized heat shield bolt notwithstanding, this is probably one of the easier jobs to do for a weekend mechanic.

 

And yes, I am aware of the value I recoup selling the used cat to the recycler (I even saved the broken bits in a bag). I have a 99 E-class Benz and all 4 cats failed and after reselling the used cats, I saved over half of my initial replacement purchase. Hope that's still the case (the CARB cat is $250 versus $100 at Ebay for 49-state). Thank you, California. =)

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Haha, gotta love that CARB designation!

 

Since everything else came down easily, I'd probably share the same stubbornness and try to conquer, too. Got a pic of the space you're working with?

 

I'll take pics the next time I go underneath. But I have small hands and it was very difficult to get a wrench on it. Did I say small hands? "I guarantee you there's no problem. I guarantee you." LOL!

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Remus92, was your stubborn bolt the one on the underside too? And I assume that bending the shield out of the way was relatively easy?

Yes. I may have had 2 stubborn ones and given the location i couldn't get enough force to just break the heads off. Certainly at least 1 on each side.

 

I used a long socket extension and just bent them enough to gain access to the bolts. A small pry bar probably would work better. The replacements didn't have the spots to attach them again so i was not worried about damaging the shields.

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Can you see the bolt?

 

 

Sent from my iPhone using Tapatalk

 

Yes.... it taunts me and reminds me what a failure I am.

 

Seriously... lol! There's about a 2-3 inch gap. I could put a 10mm box wrench on it but no leverage (yes, I've tried mating it to another wrench). I've even McGyvered a 10mm socket (grounded it down and attached it to 1/4 inch breaker bar (attached to a pipe) but that didn't break it (slipped a few times near the end of my frustration hence the rounded head).

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Yes.... it taunts me and reminds me what a failure I am.

 

 

Jack it up as high as you can safely and get you a hammer and chisel. You can probably find a long chisel or punch and get you a little short handled sledgehammer at Harbor Freight. Then beat that sucker until there's nothing left!

 

 

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Edited by onespiritbrain
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Man that sucks, I hate getting stopped up by a single buggered bolt like that! Hope you get it.

 

Regarding the mysterious second cats/resonators IDK the details but it must either be a CA emissions thing or at least vary by model year? Like I said, mine definitely weren’t cats. And strangely, I can find both cats and resonators when searching for parts even for the same year? It’s weird.

9728b590731189c6de25959f0e44e881.jpg657cf6f03b1bf0f0c0d6caaec4bf154f.jpg

 

 

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That is interesting, but probably not too surprising. There are model variations for "CA" and "FED" emissions, which wouldn't surprise me if some regions came with the resonators where they weren't mandated. I always saw those designations for my Frontier, but there was never a difference on the emissions parts. Does yours have resonators like that? My truck was originally sold in AZ and has all cats.

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MIne had what looked like the cat in the first picture, but it was hollow inside like a resonator. When I got my truck it had an exhaust leak on both sides because the cat/resonator was splitting at the seam. I first thought they were cats that would need replacing, but when I took one off and realized it was hollow I just cut them off and welded in some straight pipe. Its an 03 originally sold here in Delaware.

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  • 5 years later...
On 12/18/2017 at 4:16 PM, Remus92 said:

Yes. I may have had 2 stubborn ones and given the location i couldn't get enough force to just break the heads off. Certainly at least 1 on each side.

 

I used a long socket extension and just bent them enough to gain access to the bolts. A small pry bar probably would work better. The replacements didn't have the spots to attach them again so i was not worried about damaging the shields.

I am about to do the exact same thing this weekend,

i didn't take into account the heat shield and when we got it up on the lift... luckily i had the trailing arms to replace too so i went ahead and finished that.  I'll hit this again next Saturday and see if they all come loose, and i will do my best to destroy the heatshield, lol.  I was thinking about getting the sawzall involved, but i dont think it'd fit

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