Pearl93VE

iTrader: (14)

Hey guys, I've been banging my head against the wall trying to figure out this rattle. I've read through Rochester's Mystery Rattle thread as well as the other dozen that are out there and I think I've pinpointed it.

I took all of the lower section heat shields off and took a video of the rattle. I roll my creeper up to the front bank precat and it appears the sound is coming from there, but it's actually coming from the rear bank.

http://www.youtube.com/embed/rdVYpR-GUPE

It's still hard for me to pinpoint if it's the actual precat deteriorating or if it's the upper heat shield.

Have you guys had problems with the little shield connected to the actual precat making noise? Should I rip out all of the upper shields as well or do you think It's time to gut the cats?

Thanks in Advance.

nismopc

iTrader: (3)

A/C pulley.


Minds 2x as loud, but still works.

Pearl93VE

iTrader: (14)

Really? Does it rattle like that on the down rev? Right around 2500rpms or so coming back to idle? I had crawled underneath of it while it was being revved and could have sworn it sounded like it was coming from the rear precat, but maybe I'll double check the A/C compressor pulley again.

Professor

iTrader: (4)

Mine rattles on the rear pipe where it goes thru the rear suspension. sounds like a bearing or something gone wack

nismopc

iTrader: (3)

Yes, pretty confident on this one. Spray some WD40 or something right in there as best you can. More than likely the sound will go away for a lil bit. Mine comes back in a few minutes if I do that. This is how I found out it was the pulley...

...only on decel do I here it. Pulley appears to be loose and rattling as engine decels, but on accel the belt is tension on pulley which causes the looseness to not be there.

Pearl93VE

iTrader: (14)

Here it is at the compressor:

http://www.youtube.com/watch?v=lpC5Q...ature=youtu.be

Here it is at the rear Pre-cat:

http://www.youtube.com/watch?v=XIdUK...ature=youtu.be

I'll try to do the WD-40 trick and see if it helps but it definitely sounds more prevalent at the rear cat no?

altezzablazes

I still the rattle i gutted the cats and removed the heat shield

03blackSE

That's the exact same sound I have! I've been having it since August/September. From my examination on a lift and research on the forum, I'm about to gut my pre-cats. Just got my anti-foulers in the mail. Gonna try to get some time off work and do it before the holidays.

Besides the sound, the car runs great.

Rochester

iTrader: (3)

Ripping out the heat shields is easier said than done, but go ahead and do that first. No harm, no foul.

The majority of my mystery rattle was actually the idle tension pulley. Since selling the car to merovi, he had a similar issue with his alternator pulley, which was resolved after replacing the alternator. However, now he has a very faint but similar noise coming from the AC pulley. And since AC compressors are expensive, and it functions, I don't think that's high on his list.

Anyway, none of those rattles sound like what I'm hearing in your video. And all those pulley bearing noises in my old Max were going up-rev from idle, not down-rev into idle, like your noise. That doesn't mean it's the only way a pulley can make noise, that's just the way it was in my car.

Although that was a pretty cool underside video.

Pearl93VE

iTrader: (14)

Same here, car runs like a champ otherwise. If it's also worth noting, when the car is cold it doesn't do it. Say I move it out of the driveway to let my mom out and put it back, it shuts off nice and quiet. Only when it's 1/4+ to operating temp does it make the noise.

There have been some other videos posted over the years with very similar down rev rattles and to my knowledge there hasn't really been any definitive answer. Best bet is to crawl under there and see if you can pinpoint it. A stethoscope would be nice to put on the precat to see if it's exaggerated.

No kidding, the bottom shields were no big deal, but the upper one is a PITA. There is one bolt I couldn't get out in between the front and rear bank just above the rear bank o2. I can't for the life of me figure out how to get a wrench on without dropping the Y-pipe since I don't have any wrenches that will fit up there (and even if I did I wouldn't be able to turn it) I might just snap the bolt off coming through where the nut is welded on to the bracket and try drilling it out.

Although I couldn't remove the upper shield completely I was able to finagle it around enough to cram some pieces of rubber in-between where the pipe meets the shield. Though the noise is still identical...

I got a quote from a shop a couple weeks back to gut all three cats for $150, though I'll probably just have them gut the pre-cats and leave the downstream one alone for now.

Rochester

iTrader: (3)

Yep. IIRC, my mechanic put a long chisel on the end of his impact gun, and just cut the heat shield around that bolt.

Must be nice to have all the right tools.


That's a very fair price, because it could take them the better part of a day to do this job... unless they've done it enough times to have developed some efficiency techniques.

I wouldn't recommend gutting the main cat. It will likely smell funny, and there is an ecological consideration. Of course, that last concern is splitting hairs considering I'm OK with gutting the pre-cats.

As for the CEL, while I was using an old O2 SIM that NmexMAX sold me, the non-fouler extension sure does seem to work well on the Maxima.

Good luck.

03blackSE

Just wanted to update this thread with my results. As I posted previously in this thread, I was having the exact same sound the OP was having as the rpm's drop or I turn off the engine.

Today I got my rear pre-cat gutted and the rattling sound is now gone. When the flex pipe was removed it was evident the material inside as a whole unit had detached from the housing and was moving around a lot. Some pics for your enjoyment (excuse cellphone quality).

Near the start of gutting:



Some work done:



Gutted:



Insides out:


Unfortunately, I got to the mechanic a little late today and he didn't have time to gut the front pre-cat (doesn't rattle yet) and install my O2 sensor extender. As a result my SES light came on the drive home.

Cars runs great and feels like it breathes better (could be placebo). I used to have the well known knocking sound at 1800-2000rpm with light throttle but that has been reduced dramatically with the gutting.

Hoping to get some time before the holidays to gut the front pre-cat and install my O2 sensor extenders.

DjHackStyle

I just went through this ^ on sunday the rear precat had the same exact problem, guess its defective, show me the o2 extender u purchased. BTW ive driven 100 miles in 3 days with no non fouler or sim and no CEL.

http://forums.maxima.org/5th-generat...front-not.html

03blackSE

That's weird your SES light hasn't come on after three days.

I bought these anti-foulers.

Although, I saw cheaper options that someone posted from Summit racing after I bought mine of course.