precat rattle?
07-18-2011, 12:45 PM
#1
precat rattle?
So on my way to bishopville md i started to notice a weird rattle noise while driving it seems to only happen on an intermintant basis.i have been unable to force the car to make the sound by reving the engine or driving at a slow speed where i could catch a recording of it over the megan exhaust.this sound has me kind of worried because i have never herd a sound like this comming from any of the maximas that i have owned. the Fact that i am unable to get the sound to replicate while reving the engine upto around 4k way over the range of rpm that i normally drive and the fact that driving around 25mph does not produce the sound is what worries me.the issue seems to be around the 50-60 mph range and it does it for a few seconds at a time and stops.oil level is not a issue i change it every 1500 miles and i changed it the night before my tripon a side note i think i need a oil pan it has the appearence of sweating oil because the only place there is any sign of oil is on the bottom of the pan and it is quite rusty looking but other then that i dont find a reason for the sound.
07-18-2011, 01:25 PM
#2
I've been chasing a similar noise, although mine occurs from idle to 1500, and my mechanic couldn't pin it down with a listening tool from both above and below. Very frustrating.
It's been suggested (just 2 days ago, in fact) that the noise is coming from one or both precats, but not in the way you would think. If there is substrate material loose in the precat, conventional thinking is that any "rattle" you'd hear is the material shaking around like a maraca. However, Tunermax3000 suggested that instead the compromised precat is creating an acoustic effect at a particular RPM and exhaust pressure. Like a flute. Or a whistle... you know, like a police whistle with the little resonator ball in it. Do you follow?
So today I asked my mechanic about that, and he says that's entirely possible, particularly since he couldn't isolate the exact source of the noise except to say it was in the general area between the y-pipe and the main cat. Based on all this, I'm having my precats gutted next week, and installing an O2 sim to compensate.
I don't know if this little story applies or helps, but it might give you more to consider.
It's been suggested (just 2 days ago, in fact) that the noise is coming from one or both precats, but not in the way you would think. If there is substrate material loose in the precat, conventional thinking is that any "rattle" you'd hear is the material shaking around like a maraca. However, Tunermax3000 suggested that instead the compromised precat is creating an acoustic effect at a particular RPM and exhaust pressure. Like a flute. Or a whistle... you know, like a police whistle with the little resonator ball in it. Do you follow?
So today I asked my mechanic about that, and he says that's entirely possible, particularly since he couldn't isolate the exact source of the noise except to say it was in the general area between the y-pipe and the main cat. Based on all this, I'm having my precats gutted next week, and installing an O2 sim to compensate.
I don't know if this little story applies or helps, but it might give you more to consider.
07-18-2011, 02:12 PM
#3
Sure does apply.i had figured it was comming from inside the precats because the heat shields are in pretty ok shape i used a pry bar to see if i could persuade any of them to move around freely and had no luck.i really hope it is the precats because i had posted a few weeks ago about the car feeling sluggish and unresponsive and i have replaced all of the normal culprits Plugs,Maf,6 new coils,fuel pump and filter and even the vias sol. so im hoping it is the precat because a cutting and gutting i will be doing.i would like to weld up a nice stainless unit like i had on my old 03 that was stolen from me but after y recent round of welders eye i think gutted will be just fine for now if that is the problem found.
07-18-2011, 03:24 PM
#5
I've been chasing a similar noise, although mine occurs from idle to 1500, and my mechanic couldn't pin it down with a listening tool from both above and below. Very frustrating.
It's been suggested (just 2 days ago, in fact) that the noise is coming from one or both precats, but not in the way you would think. If there is substrate material loose in the precat, conventional thinking is that any "rattle" you'd hear is the material shaking around like a maraca. However, Tunermax3000 suggested that instead the compromised precat is creating an acoustic effect at a particular RPM and exhaust pressure. Like a flute. Or a whistle... you know, like a police whistle with the little resonator ball in it. Do you follow?
So today I asked my mechanic about that, and he says that's entirely possible, particularly since he couldn't isolate the exact source of the noise except to say it was in the general area between the y-pipe and the main cat. Based on all this, I'm having my precats gutted next week, and installing an O2 sim to compensate.
I don't know if this little story applies or helps, but it might give you more to consider.
It's been suggested (just 2 days ago, in fact) that the noise is coming from one or both precats, but not in the way you would think. If there is substrate material loose in the precat, conventional thinking is that any "rattle" you'd hear is the material shaking around like a maraca. However, Tunermax3000 suggested that instead the compromised precat is creating an acoustic effect at a particular RPM and exhaust pressure. Like a flute. Or a whistle... you know, like a police whistle with the little resonator ball in it. Do you follow?
So today I asked my mechanic about that, and he says that's entirely possible, particularly since he couldn't isolate the exact source of the noise except to say it was in the general area between the y-pipe and the main cat. Based on all this, I'm having my precats gutted next week, and installing an O2 sim to compensate.
I don't know if this little story applies or helps, but it might give you more to consider.
get ready for a better sounding exhaust and a pretty nice power gain buddy.the rear bank pre cat is a total pita and your mechanic is going to curse you for it though
07-18-2011, 03:30 PM
#6
Like the OP, all I want is for this mystery rattle to go away. I'm really not expecting any power gain, although that would be nice. If I were motivated to achieve added power through a modded exhaust, I'd get rid of the Cattman y-pipe and install a set of headers.
Either way, I'll come back to this thread in 10 days with feedback. Until then, I'm very curious what cjandura does.
07-18-2011, 03:45 PM
#7
I'm pretty sure you have that backwards. The rear-most precat can be gutted while still on the manifold. It's the front-most precat that has the bend in it.
Like the OP, all I want is for this mystery rattle to go away. I'm really not expecting any power gain, although that would be nice. If I were motivated to achieve added power through a modded exhaust, I'd get rid of the Cattman y-pipe and install a set of headers.
Either way, I'll come back to this thread in 10 days with feedback. Until then, I'm very curious what cjandura does.
Like the OP, all I want is for this mystery rattle to go away. I'm really not expecting any power gain, although that would be nice. If I were motivated to achieve added power through a modded exhaust, I'd get rid of the Cattman y-pipe and install a set of headers.
Either way, I'll come back to this thread in 10 days with feedback. Until then, I'm very curious what cjandura does.
no way man you wish it was that easy.rear bank you need to drop the y and get a few bolts from behind the im and some from underneath..When you get the rear bank pre cat dropped you need to put it in a vice and use an air chisel to get the mesh out which is the worst part and time consuming of the whole job.the front cat under the water pipes is the easiest because when you drop it..you give it a few wacks with a hammer and a pry bar and it crumbles out real easy,When it's done you should get almost the same amount of power as having header's...do you have a test pipe already ??
07-18-2011, 03:47 PM
#8
I'm pretty sure you have that backwards. The rear-most precat can be gutted while still on the manifold. It's the front-most precat that has the bend in it.
Like the OP, all I want is for this mystery rattle to go away. I'm really not expecting any power gain, although that would be nice. If I were motivated to achieve added power through a modded exhaust, I'd get rid of the Cattman y-pipe and install a set of headers.
Either way, I'll come back to this thread in 10 days with feedback. Until then, I'm very curious what cjandura does.
Like the OP, all I want is for this mystery rattle to go away. I'm really not expecting any power gain, although that would be nice. If I were motivated to achieve added power through a modded exhaust, I'd get rid of the Cattman y-pipe and install a set of headers.
Either way, I'll come back to this thread in 10 days with feedback. Until then, I'm very curious what cjandura does.
07-18-2011, 04:17 PM
#9
Besides, the car is configured just fine as it is. Gutting the precats isn't a mod for me... I'm intending it as a cost-effective fix to a problem.
07-18-2011, 04:23 PM
#10
no way man you wish it was that easy.rear bank you need to drop the y and get a few bolts from behind the im and some from underneath..When you get the rear bank pre cat dropped you need to put it in a vice and use an air chisel to get the mesh out which is the worst part and time consuming of the whole job.the front cat under the water pipes is the easiest because when you drop it..you give it a few wacks with a hammer and a pry bar and it crumbles out real easy,When it's done you should get almost the same amount of power as having header's...do you have a test pipe already ??
Remember, I'm not doing the work. I've got a good street-pro mechanic, who's very sure he can gut the rear while it's still on the manifold. But not the front, for obvious reasons.Test pipe? No, the main cat can continue doing what it does. In fact, keeping the main cat is how I rationalize gutting the pre-cats... environmentally speaking, I suppose. From what I understand, the pre-cats are there to introduce catalyst right away to the exhaust, before the main cat has a chance to heat up, after which the main cat carries most of the load.
Guys... this isn't my thread. Sorry, cjandura. I didn't set out to ***** your conversation.
Last edited by Rochester; 07-18-2011 at 04:26 PM.
07-18-2011, 04:33 PM
#11
Not looking for power gains here.i just want the crazy noise gone and as far as a better sounding exhaust i think gutting the cats may make it louder which is something i dont want i already have a raspy terrible sounding megan exhaust with loads of drone.i had done the eastren front precat on my old maxima after the 4th one i made my own they dont fit right at all and making both precats only cost me about $150 to do and they were metal core and 2.5" stainless units.
07-18-2011, 04:40 PM
#13
Hmm. Remember, I'm not doing the work. I've got a good street-pro mechanic, who's very sure he can gut the rear while it's still on the manifold. But not the front, for obvious reasons.
Test pipe? No, the main cat can continue doing what it does. In fact, keeping the main cat is how I rationalize gutting the pre-cats... environmentally speaking, I suppose. From what I understand, the pre-cats are there to introduce catalyst right away to the exhaust, before the main cat has a chance to heat up, after which the main cat carries most of the load.
Guys... this isn't my thread. Sorry, cjandura. I didn't set out to ***** your conversation.
Remember, I'm not doing the work. I've got a good street-pro mechanic, who's very sure he can gut the rear while it's still on the manifold. But not the front, for obvious reasons.Test pipe? No, the main cat can continue doing what it does. In fact, keeping the main cat is how I rationalize gutting the pre-cats... environmentally speaking, I suppose. From what I understand, the pre-cats are there to introduce catalyst right away to the exhaust, before the main cat has a chance to heat up, after which the main cat carries most of the load.
Guys... this isn't my thread. Sorry, cjandura. I didn't set out to ***** your conversation.
I have to apologize for jacking the poor guys thread but it's not possible to gut the rear cat while it's still on the car.If your mechanic hasn't done one yet like mine..he is going to have quite the job in front of him.And i know you aren't doing this to make power, but with the mods you have it should give your car a pretty big kick in the pants.Just look at my dyno thread i posted a while back and see the #'s for yourself.
07-18-2011, 06:44 PM
#14
Well its the front precat what i did was take the Mic i use for my audio processor in the car and hook it up to my droid first i did the rear precat by just hooking the Mic to a dow and clamping it to the intake got the car up to MPH rattle started i could hear it but the rta app on the phone recording showed nothing.So i pinned it to the coolant lined above the front precat and got the noise back bang it showed right up on the rta app and herd it clear as day on the playback.Now unless there is something else in that front area that can make a rattle metallic noise i think Ive got it .now i only hope the temporary gutting of it will show me some mercy and get rid of the sluggish issue I'm having.
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