Anybody in the mood for some chinese? I have the week off and i really need to address this clogged cat issue. A few weeks ago i tried to just remove the main cat but i was unsuccessful. I couldnt break loose the nuts to save my life so i said forget it. I have 5 days off so that for me is Plenty enough time to take on this job but the most ive done to this car sofar is an intake bop and strut bar lol none of which compare to the work envolved with removing the manifolds.

I guess where im getting at is i have the general concept on how to remove both of them but what EXACTLY do i need to do to successfully conquer this job. Its looking like i need to take the UIM off and some lines running infront of the front manifold...I really just need a how to step by step ( yes im looking to be spoon fed) lol just basically tell me what i need to remove first to easily get to the mani bolts...

Any info is much appreciated, my main cat is smelling really bad and id love to gain some power back and also fuel economy. Im pretty well mechanically inclined, ive worked at a body shop for the past 5 years so im used to turning wrenches on a daily basis im just a little timid on working on this car because its fairly new to me and i dont wanna mess s*** up lol Thanks again!

 

Were you going to replace the CAT?

 

just going to gut all 3 of em.....so basically from what ive read i just dissconnect the neg battery cable. Take off the exhaust from manifolds back, then take off heat shields and then take off both manifolds... Are all the bolts for the rear manifold easier to get to from the bottem? my only problem is that all of my bolts and studs are extremely tight and are going to probably need heat to loosen up...

 

No reason to d/c the battery. Couldn't hurt, but no reason for it. I hate re-setting my radio channels, equalizer & clock.

No reason to remove the intake manifold either.

Tools check:

Jack stands, more than 1 jack, sockets, crows feet, PBlaster, maybe some heat, patience & new gaskets.

Instead of gutting the main cat, I'd get a test pipe.

 

yea i was going to buy the test pipe off of brett but right before i purchased it i went out to my car and tried getting the main cat off..... needless to say after buying brand new 6 point sockets and also the grip tight sockets i couldnt get those damn nuts to budge

o and i also had a propane torch on 1 of the nuts untill i thought my cat was going to catch fire lol and still no go..

 

I use a grinder whenever I run into that problem. Sucks.

 

I used a grinder on one off the bolts. If you have to use the cat again you can drill it out and use nuts and bolts. I am scared of running into the same thing when gutting my cats. Not to mention taking the O2's off to install the plug fouler.

 

I don't want anyone to be fooled here. This is not a "just do this and just do that" kind of job. For the average DIYer, this will probably be a painfully, time-consuming, and frustrating job. Your rear precat is going to be a PITA if you still have your manifold heat shield in place. The heat shield itself can make grown men cry. I've seen it. Under that rear heat shield there are four bolts which do not offer easy access with a torch. Two must be loosened from the top and two from the bottom.

+9308218395741239 on what Nmexmax said. Lots and lots of patience. Even when you get that rear precat dropped, it's going to take you quite awhile to gut if you don't have air tools (chisel, hammer, etc.). The front precat is a lot easier IMHO.

Cliff notes: Give yourself time. Be realistic about your abilities and evaluate your time costs before choosing to do this yourself.

 

nelledge is writing with good, common sense. (Typical, yeah, but there it is anyway.)

After researching the heck out of this, then recently having had my precats gutted by a skilled mechanic, I would describe this job as one that even most mechanics wouldn't want to do. As a DIY project, you will need skills, tools, and more patience than most. If that describes you, OP, then more power to you.

As for the whole test-pipe thing for your main cat, double-check the emissions testing regulations in Maryland before committing to that. Some states read codes, some sniff, some do visual inspections, and some just don't care.

 

This. We sometimes forget our state legislation differs vastly from other states.

It happens, periodically.

 

well good thing is here in maryland when you get inspected once thats it untill you sell the car so im fine when it comes to that...The only reason i really want to do this is because i want headers in the future but money is funny right now. Regardless tho my main cat is smelling up a storm and my fuel economy has gone down a little since i purchased the car in Nov. so with that said id like to go ahead with gutting the pre cats so that when it comes time to do headers ill be ahead of the game already...I do consider my self pretty mechanically inclined but my patience level is pretty low and i do get frustrated easily so who knows i might give it a try but this week is half way over and i have a busy birthday weekend planned so this might have to wait a little bit unless i get some fire under my a** lol

 

Ha'll righty fellers im goin in lol, tired of procrastinating. i just took off both front little splash guards and i just sprayed down the y pipe to manifold bolts so we shall see how far i can get tonight before i get frustrated lol. If and when i do get these things off and gutted i will need to go get (2) o2 sims correct?

 

IMO, the manifold heat shields(especially the rear) should be the first thing you attempt. Don't get me wrong, spray all the fasteners down with PB Blaster. However, dropping the y is going to **** you off if you can't get to the upper precat bolts.

Also, there are numerous members that have had luck with the anti-fouler modification to take the sensor out of the direct stream. It's cheaper and you don't have to wait for shipping since most auto part stores carry them.

 

thx for the info nelledge, i got the front 3 ypipe bolts off and i was working on the rear 3 and i got them all off but 1 stud stayed in the precat, now im trying to remove the ypipe totally but the 2 nuts on the main cat flange are being real a** holes right now!

 

Thought this might help you out a bit

http://forums.maxima.org/5th-generat...-pre-cats.html

 

Everybody pretty much covered it....me did the job twice and once for the front one and then went back to do the other another day, pain in the @$$ but a good difference you can feel...car got totaled so waiting for my headers to throw on a 02 Max since my 03 is gone.....Good luck and patience is the key.....

 

A cut off wheel works better! When I first saw the title, I froze with a dirty grin reminscing about a former female friend of mine talking about hanging out one night together while she wears her CAT Cutter jeans.....

 

So many people gutting their pre-cats all of a sudden.

What's up with that? Feels like a new 5th gen fad.

 

Monkey see.....Monkey Do??????

 

Naw, it's just the Pied Piper up to his old tricks.

 

^^^ lol im just doing it to cheaply improve gas millage and to gain a little hp back. Its just that everyone here lately gutting their cats has given me the motivation to go ahead and do this my self...

btw i got the front cat and manifold off about 30 minutes ago but i had to soak the cat to manifold bolts because they were too tight to budge...ill start back up on it tomorrow morning. I still have to get the front two nuts off of the main cat to get the y-pipe away to drop the rear manifold so maybe the torch will come into play we'll see

 

A section of my front exhaust manifold heat-shield had to get cut away for access to the front bolts... because there was no removing it in any reasonable way that would allow for that POS to get re-attached. And the heat-shield around the front pre-cat... that was simply ripped out. Buh-bye.

036mtmax is my Pied Piper, man. And Tunermaxima3000 was my inspiration, who convinced me (in person) that the mystery rattle was coming from my pre-cats. Of course, he was actually wrong , but that's how I got here.

No regrets. Nice mod. Would probably rather have headers, but already had the Cattman y-pipe and blah blah blah.

Pied Piper, LOL.

 

I would submit that it is a product of the economic times: ****-poor economy, high unemployment, relatively expensive fuel... Obamanomics at work, baby! If times were better, I'm sure a greater percentage of people would have money to buy headers. In all seriousness, though, we should just buy the headers anyway - and then hand the bill to our children. I mean, who really cares about the long-term future or something called a credit rating?

Speaking of the Pied Piper, I give BHO a break, though: he inherited this problem and all he's been trying to do for the past four years is get [re-]elected! That, and golfing a lot...

(yup, that one was for you, Rochester)

 

I would submit that it is a product of owning a 10 year old car.

As to your political discontent... meh. You're entitled to your own interpretation of recent history as it applies to the economy. Like anything else, the more informed you become the more accurate the assessment. So good luck with that.

 

welp i got the front cat apart from the manifold this morning, only messed up 1 bolt holding the cat to mani so thats not too bad, gutting the cat was a cake walk compared to just getting the thing out of the car lol im about to put it back together and start on the rear cat now but i figured id post a couple pics real quick...<br>
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sorry about picture size i need to figre out how to resize lol

 

why teh *** you got the pics horizontally positioned?!

 

You removed the entire manifold, eh? I recall reading some recommendations for that approach being easier than just removing the pre-cat.

With the manifold off the car, have you considered having it sand-blasted, then painting it with something like POR 15 Black Velvet?

Neat pictures, OP. Can't wait to see the pictures of the rear, no doubt covered in sweat and blood. Keep going!

 

So far so good, looks like you almost finish it. The rear headshield was PITA. Make sure you "enter or put <br> between pictures so it doesn't run acorss the screen.

 

...i though this was interesting that your random typing equaled a possible cc number

 

lol i frikked up on the pics my fault. i havnt actually put any thought into making this stock front manifold "look" any better just getting it to breath better was my #1 priority but its a thought... im just going to leave the heat shield off of it tho i dont see much need for it, also to get the front manifold and cat out in 1 peice youll need to take the radiator fans out and dissconnect the o2 sensor plugs off of that rail to be able to slide the whole thing out from the top but it was no biggy.

Now onto the back 1, i just dropped the y down ( it is still connected to the main cat tho) so its just hanging but its out of the way of the cat so were good... I was looking at this rear cat ( its alot smaller than the front 1 and also mounted differently. it has 4 bolts total holding it to the manifold, 2 from the bottem and 2 from the top. If the inside wasnt as hard as metal then i would just gut it on the car but having the car jacked up and im laying on the ground doesnt leave much room to swing a hammer. I could wait for my buddy to get off of work to bring me my air chisel from work but i dont think ima need it.

By the looks of it i should be able to get the rear heat shield off of the manifold to expose the other 2 bolts that are coming in from the top, then i can easily undo the 2 bottem bolts and drop the whole rear cat while leaving the manifold intact. Im about to go back in and see what i can figure out! Thx for the picture info The6spMax ill keep that in mind for my next pictures to upload!

 

I would rethink this. Wait for your buddy to bring the air tools. You can thank me later.


Now I have to go check other threads and see if I left my security code or social.

 

so what are the chances that i get debris into the exhaust ports if i do use the air chisel?

 

I meant drop the precat and then use the air chisel. Too much risk vs reward in doing it on-car, IMO.

 

Why did you take off the manifold instead of just dropping the pre-cat itself ? you just made that job 10 times harder than it was dude.And again you can't gut the rear pre-cat on the car,Use a respirator of some sort the powder the inside of the rear cat puts out when chiseling it out makes a mess and it's extremely harmfull to breathe in.

 

You keep saying that like it's true.

 

lol i dont see how just taking the manifold off makes things any harder, it was alot easier to get to the six cat bolts with the whole thing off i guarantee that. But anyways i cant seem to get enough room or the right angle to get to the 3 10mm screws holding the rear heat shield on, thats the only thing stopping me from getting the rear cat off.Im sure a swivel is the tool of chice in this case but im having no luck lol bout to go take another hack at it..

 

Trust me it is i watched the whole pain staking process unfold right in front of my eyes My mechanic said next time he does one he's going to remove and cut the rear bank pre-cat in half, remove internals and re-weld.Much easier than chiseling and hacking at the cat for an hour.

 

A really long extension with a swivel,it's tough to get access behind the im but that's how my mechanic did it.Taking the manifold off is just more bolts and you run the risk of snapping more bolts and or future exhaust leaks...F all that noise

 

Good progress.


At least he's doing something to his car

 

I just don't understand why you dropped the manifold with the pre-cat connected?? All you had to do is remove the heat shield and take the bolts off from the top and bottom of the pre cat