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How hard to replace Cat and DP?

 
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Ollie2003LS
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PostPosted: Wed Mar 28, 2012 7:41 pm    Post subject:  How hard to replace Cat and DP? Reply with quote

It looks as though we may need to replace the catalytic converter. Weíve had no change in performance after replacing the MAF and EGR valve (though the CEL says that these were bad). The car still suffer from sluggish acceleration and stumbles or wonít start on hot restarts.

The local muffler shop says he doesnít believe in back-pressure tests and that the only way to know is to take it apart and check it for blockage (at that point I'd guess Iíd need a new converter anyway Rolling Eyes )He sayís heís familiar with Impalas and can weld in a new cat for $350 (decent price?) and promises the carís computer will ďacceptĒ it. If I went the ZZP rout it looks like I could get out for around $200.

I would like to know...

1. Whatís the easiest most fool proof way to check for a clogged cat (if there isnít a code present.) I donít have a backpressure gauge and o2 adapter and I donít really want to drill into exhaust system. Can I take a vacuum reading somewhere to get a good idea?

2. How hard is a new DP and Cat to install. I know itís just some gaskets and four bolts, but is it hard to install one of these leak free. Can I use copper sealant along with the gaskets to insure no leaks the first time. Car has no rust issues so Iím not too worried about stuck bolts. Iíve done the radiator, water pump and plugs far, so Iím not completely mechanically inept, but would like to know if this is harder than it looks. Also, will ramps in the front give me enough access?
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2001Ls
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PostPosted: Wed Mar 28, 2012 11:11 pm    Post subject:   Reply with quote

I just got my replacement cat in the mail today. It's a magnaflow 23405. I got it for $168 from magnaflowdeopt.com. (they seemed shady as they don't pick up the phone, dont email an order confirmation), but it showed up at my door. Came with new gasket and ring which are the two needed parts for install.

The install is very staight forward. 2 bolts at cat/ resonator and 2 bolts at exhaust manifold/cat. The only problem is if the bolts are seized. I have been trying to take my old cat off for the past 2 days to clean it out before I installed the new one: the 2 bolts at the resonator were very easy to take off (car has to be raised) and the rear 02 sensor unclips from its harness easily. The two bolts on the exhaust manifold are very tight. I have climbed up ontop of my engine to reach them (after rocking the motor forward after undoing the motor mounts) but still cant get them loose. I am going to give them a couple of rounds of pb blaster tomorrow then try again.

To know that your cat is clogged, you will feel a very obvious sluggishness.

Like this video I made here-> http://www.youtube.com/watch?v=F4xJLb9SnZ4
Also your car won't rev past about 3k.
And if you really want to check it out, put your car up on ramps or jack stands, climb underneath and bang on it. I would definitally sugest this to know if its clogged. If you hear something that sounds like gravel moving around that is the catalyst honeycomb material all broken up and that causes resttriction. Also you could unbolt the resonator from the cat, bang on it, and if pieces start falling out its prob clogged. I basically gutted the cat by unbolting it at the resonator and banging all the loose material out of it. Car moves quickly again. I'm so much happier.

I am not a mechanic, I have done oil changes, air filter, spark plug, blower motor and ignition switch on this car because I enjoy it. I decided to tackle this job on my own because I will be happy that I learned how and accomplished something. If you are able to do those basic things, have 2 ratchet sets, and have a way to life the car you should be capable of doing this job. It is your decision.

Also on a side note I think that the aftermarket cats set off a p0420 code eventually. I am going to buy an o2 sim if this happens or try to mcguyver a way to pass the inspection. If I left anything out or you have any questions let me know... I am going to try to install the cat tomorrow and I don't forsee any problems except getting those 2 damn bolts loose @ the exhaust manifold. Also I want to try and find new bolts for the install so everything is shiny and new.

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00impala123
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PostPosted: Thu Mar 29, 2012 12:36 am    Post subject:   Reply with quote

Its pretty easy. Hardest part is reaching the rear mani to DP bolts and getting them loose. remove the STB and rock the engine forward and you'll be good

You can use the copper sealant but it isn't necessary.

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Ollie2003LS
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PostPosted: Thu Mar 29, 2012 9:00 pm    Post subject:   Reply with quote

Thanks for your detailed response 2001ls.... I think you about hit on all the questions I had.Clap Let us know if the Magnaflow fits correctly and how it works out. Iím now thinking of going with one instead of the ZZP. Did the gaskets come with the factory box or did the site you ordered them from include them as extras?

You mention it only needing a flange gasket and the inset ring gasket. Do I need a new gasket for the flange where the cat meets the resonator also? I havenít looked down there yet, so I might not be describing this right.
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2001Ls
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PostPosted: Thu Mar 29, 2012 10:43 pm    Post subject:   Reply with quote

Ollie2003LS wrote:
Thanks for your detailed response 2001ls.... I think you about hit on all the questions I had.Clap Let us know if the Magnaflow fits correctly and how it works out. Iím now thinking of going with one instead of the ZZP. Did the gaskets come with the factory box or did the site you ordered them from include them as extras?

http://tradestuffup.blogspot.c.....-2001.html

check out that link above, it is a how to on 3.8 cat replacement with pics and directions


You mention it only needing a flange gasket and the inset ring gasket. Do I need a new gasket for the flange where the cat meets the resonator also? I havenít looked down there yet, so I might not be describing this right.


Going to try and get the bolts @ manifold loose again on sat bc I am working tomorrow. The site I ordered from shipped the unit in a plain white box which has a magnaflow tag on it with the part number. The box has a plastic bag in it with the "ring " which goes on @ the manifold and a gasket where the cat meets the resonator. The baggy has a magnaflow warranty card and both gaskets say magnaflow in thier little packages.

To answer your last question there is a thin metalish material gasket that goes between the resonator and cat. And if I am not crazy the little metal ring sits inside of the cat @ the manifold and there is no other gasket. But I assume this is the case because they included the other hardware so It seems silly to leave out a gasket.

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2001Ls
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PostPosted: Sun Apr 01, 2012 12:27 am    Post subject:   Reply with quote

Update

I replaced the cat today. Took it to a shop and he cracked the bolts @ the manifold with a torch (which I dont have). Put new gasket on @ reonator and new bolts there. Used new nuts @ manifold connection. Somewhere there is a leak though as I can hear it. I tightened the new nuts and bolts like hell and there is still this leak which is going to require another hour or two on my part. Kinda sucks, just wanted to post how its going nothing is ever as easy as it seems on a car.

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2001Ls
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PostPosted: Sun Apr 01, 2012 11:15 am    Post subject:   Reply with quote

Just checked it out again this morning. I have a tiny leak @ the resonator on the drivers side. I think I actually over tightened the bolts and warped the resonator flange a bit.... Time to look for a thicker gasket. But for now Im going to drive like this, theres no way to fix it really.

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