Rochester

iTrader: (3)

For over a year now, almost two, I've had this mystery rattle. It started out very faint, but once I started hearing it, I could always make it out. Basically, it's a low-end rattle, or a whistle, that sounds like a can of marbles. You hear it when goosing the engine from the idle position (which is 700 rpm in my 6MT, give or take 50 rpm.) It only lasts for a fraction of a second, because soon as the revs are over 1200, it goes away. This is why you don't hear it until the car is at running temp.

In the last few months, it got a little louder, and finally my mechanic heard it... but couldn't find the source. We tried for like an hour last month, me goosing the engine as he went all over the engine bay from the top, and from below while the car was on the lift, using a mechanic's listening tool. He couldn't localize the noise.

After a while, I became convinced the problem was in one or both pre-cats, so yesterday I had them gutted and installed an O2 Sim. It's nice and all as a power-mod to have the pre-cats gutted, but the noise is still there.

So it's not the pre-cats. And it's not the timing chain cover (because that would have been obvious with the listening tool.) It's not the main cat, because the noise is in front... on the passenger side, actually. It's not the front pre-cat heat shield, because we ripped that out... even though it's really not that kind of noise.

I'm slowly going insane.

Ideas? Anyone?

- - - - - - - - - - - - - - - - - -

EDIT: Tension Pulley replaced, and all is right with the world again.

Xpcgamer

iTrader: (5)

I am thinking you have all the pulleys and both belts on that side. Have you checked a bad bearing on one of the pulleys? Maybe remove the AC belt and drive the car and see if the noise is still there. I am sure you can't remove the other belt with out the cars electronics going nuts.

TunerMaxima3000

iTrader: (4)

Wow I am surprised. Have you listened out the tailpipe when it makes the noise?

Rochester

iTrader: (3)

Good thinking, Xpcgamer. Keep it coming.

Related to your comment about Air Conditioning... I almost never use the AC because I like open windows, but the recent heat wave has been brutal. So it wasn't until just this week that I realized that with the AC on, this rattle is much more obvious. If there's any relationship, what is it about the Air Conditioning system that could cause a "can of marbles" sound?

Rochester

iTrader: (3)

No, he didn't put it on the tail pipe. Hmm.

But you heard the noise in person, Matt... it was coming from the passenger side under the engine.

TunerMaxima3000

iTrader: (4)

The A/C compressor running would cause a load on the engine, as well as a load on the belts. I think he has a great guess going there, check those pulleys and belts.

Yes, I heard it, and I'm just combining what I heard with what your mechanic has tested. Assuming he tested all engine components with a stethoscope and couldn't locate it, that would tell me that it's an open channel or internal issue. He should have tested around the timing chain cover and hence, the pulleys.

I would ask him for clarification on that.

By open channel I mean intake or exhaust stream, a restriction or change in tuning can cause a whistling/noise that resonates through the whole stream/channel, making it hard or impossible to pinpoint the location with a stethoscope.

And I mean simply putting your ear to the tailpipe. The purpose is to see if it's resonating in the exhaust system. Even if the technician put his stethoscope on the side of the exhaust pipe before the muffler he should hear it if it's in the exhaust stream.

At this point, I think we need to isolate if the noise is external, or internal, either in the intake or exhaust, engine, or a vacuum leak or pulley/belt issue.

How long has this been going on anyways?

luvlexus101

iTrader: (6)

Just sell the thing to me and get the g37 already

UncleSmitty

iTrader: (1)

Yea I agree with the hypothesis on the belts and pulleys.

Xpcgamer

iTrader: (5)

Check those belts and the AC compressor. Maybe since you barely use the AC it needs the oil in the lines to lubricate it up a bit. Maybe continued use of the AC will make the noise go away.

Bufflomike

I am actually wondering if your belt may be a little loose and this is causing the temporary noise until the rpm's rise whereby the centripital forces allow the belt to grab efficiently again. Good luck

Shift_Max

iTrader: (18)

make a video?

Rochester

iTrader: (3)

I'll be seeing him later today to settle up for the pre-cats. We'll talk then.

See the first post. 1-2 years, with gradually increasing intensity. For the longest time it was like, "Hey, did you hear that?" LOL

Going to talk to the mechanic today about the AC possibility. I like the simple idea of removing the belt to either identify or rule out the compressor.

That makes sense, too. I'm going to suggest that in conjunction with the AC question.

Patience, Puddle-lights.

Rochester

iTrader: (3)

Um, guys... on our cars, the AC Compressor uses the main serpentine belt. It's the PS pump that has its own belt.

That doesn't mean I can't test out the theory on the AC compressor being the source of the noise, it just means disconnecting the AC belt permanently isn't an option. Because like I said, I rarely use the AC.

knight_yyz

iTrader: (40)

sure you can. you just need a smaller belt

Bufflomike

This has been done by a few folks, think there is even a thread and belt size somewhere but just find the problem and fix it is the goal I think.

Rochester

iTrader: (3)

Doh!

But the large-breasted girl from Buffalo is right... if the AC is the issue, I'll just replace the compressor.

Bufflomike

Just a pic which motivates me to post on this forum because I love that girl...dont even know who it is

Eirik

iTrader: (2)

Can you post a video of the noise, Rochester?

I'm confused: Is it a rattle or a whistle? I know you explained the noise in the last thread as the sound the little ball (whatever your vocab word of the day was) makes that is inside a whistle, but I can't rectify the noise of a can of marbles/bees in a can, which emits a low-frequency sound, with the noise of a howl/whistle, which emits a much higher-pitched noise.

My mystery rattle sounds like metal vibrating, like a tin can of marbles being shaken, and comes from the same area as yours. My serpentine belt is slipping and makes the classic squealing/squeaking noise, albeit at a fairly soft level, until it warms up.

Buying a shorter belt to test the rattle theory would be difficult, don't you think? If your battery is new enough, can't you just remove the belt and run the engine long enough to determine whether or not the sound is still there?

Edit: Hmmm... If your bees-in-a-can sound is the same as others' bees-in-a-can sound and it wasn't coming from the pre-cats, this could seriously damage the "pre-cat rattle of death" talk.

Rochester

iTrader: (3)

Not without help, and the perfect acoustic conditions.

That's exactly my next step: run the car for a few minutes without the belt. At the moment, IDK when that's going to happen. But soon, because I feel like I'm on a Quest.

I'm the guy in the middle.

01SilverMaxima

iTrader: (1)

"your mother was a hamster and your father smelled of eldaberries!" love that movie.

spock

iTrader: (5)

Hopefully you resolve this before you encounter the killer rabbit.

nelledge

iTrader: (6)

Rabid rabbit.

Rochester

iTrader: (3)

I know that rabbit. It's got a mean streak a mile wide.

Froggmann

iTrader: (6)

Surveillance photos show it has already taken out his guard cat:

Rochester

iTrader: (3)

Holy crap, we're off-topic!

That will teach me not to post a Monty Python image in this forum.

Rochester

iTrader: (3)

On topic: spoke to my mechanic today about the AC compressor idea. I'm going to wait until the end of summer, so things cool down... including the hole in my wallet. Then we're going to yank the serpentine belt and see what happens.

Until then... marbles in a soup-can, FTL.

Oh, and gutted pre-cats, FTW.

HotshotVQ35

iTrader: (5)

so that sim is working for you? i have the same sound, im pretty sure its the flexpipe on my car, when it cools down i will take a look at it, when i took pics of the y pipe like 2 years ago, all the coating was gone and the flex looked like azz

Froggmann

iTrader: (6)

I thought about that too but he has a new Cattman Y-pipe which would have a new flex on it. Not to mention I'm sure he and his mechanic would be able to correlate the installation with the noise if the flex was in fact bad.

BTW if the torque-brace is taken off does that affect the sound at all?

00MaxMayne

iTrader: (1)

I'm having a bit of a rattling problem in my car as well. It occurs around 1800-2100 rpms so its quite annoying because I hear it often. Curious as to what you're problem may be and maybe the same thing is wrong with mine.

036mtmax

iTrader: (11)

Did you check the heat sheild thats bolted to the firewall behind the rear bank pre cat ?? mine was loose before and i bent it a little away from the firewall and the noise went away..Just a suggestion though.

Eirik

iTrader: (2)

Yeah, from 036mt's thread, I found that "Courtesy has two different heat shields, a "front driveshaft" heat shield and an "exhaust manifold cover", for $45 and $30, respectively."

The "exhaust manifold cover" is the one facing the front of the car that <strike>you guys</strike> your mechanic removed during testing.

That's when mine happens, only with a slightly larger spread. Mine's sort of become even more specific and only seems to happen between 1900 and just under 2100 rpm--much higher than Rochester's mystery rattle, but still at a low enough speed that the engine crosses the threshold again and again and again during my daily commute.

Does yours rattle on the way up and down, Rochester/00MaxMayne? Mine, so far as I can hear, only happens on the way up.

Rochester

iTrader: (3)

Hey, Hotshot. So far so good, no CEL and I'm about 50 miles into it. The sim sits under the engine cover, where my VIAS vacuum tank used to be. There's a green LED.

Well, new as in 3 years ago, with maybe 20K miles on since. So, no, I suppose it's not really new at all. But new enough, I'd say.

That's an excellent question, Froggy, and one I also thought of but never mentioned because no - it doesn't matter whether the Torque Link is on the car or not.

I was under the car while it was on the lift and my mechanic checked the heat shields, and cut away the front one. That's not the issue.

Same here, only on the way up, from 700 rpm for a half-second until 1100 rpm, give or take. That's why I don't here it when the car is cold, and idling at 1200.

Again, the noise occurs more easily and louder when the air-conditioning is on. Marbles in a soup-can.

Rochester

iTrader: (3)

It's almost amusing reading how many other people live with a particular mystery rattle.

Funny aside, I appreciate all the ideas, and the support.

cjandura

iTrader: (3)

Ok Rochester i hope this helps you out a little i did a little testing today.Belt i used was a Bosch 6pk890 to bypass the ac unit.tested like this as i didnt want to stress the engine out.i went to a old empty acme parking lot and let the car cool down.i unhooked the fans so i wouldnt get additional noise.i let the car cool down 30 minutes between runs.
test #1 no belt i carefully went upto 40mph for about 5 minutes and i was unable to acquire any noise.
test #2 Short belt a/c bypassed same run was able to acquire the noise but also noticed an additional noise.
in the morning i am going to find a belt that will allow me to bypass the tensioner pulley i have a strange feeling about it only because of the additional acquired noise after swaping the belts around.and now the acquired noise has buddied up with the rattle in a skippng type pattern.my local dealer is out of the tensioner assembly but pepboys has a dayco pulley only part i may pick up also in the morning just to try out.i hope the tensioner nut is not like the last one i tried to replace.

NJ3ndri

i just had a rattle craze at work on a 2011 explorer. took me a week to find. the rattle was coming from the dash on light acceleration. removed dash found nothing. scoped the car with chassis ears. nothing good found. i found the rattle to be coming from a stripped bolt on the exhaust hanger bracket. bolt had a washer on it so it had some rattling since it was loose. this was driving everyone in the shop crazy....i got stuck with it cuz i get paid hourly lol

NJ3ndri

its probably something really stupid so just make sure everything is tight and start removing things to isolate the noise because it does travel. like i said before this bolt was underneath the car but everyone thought it was the heater core rattling or something

luvlexus101

iTrader: (6)

Thats my girlfriend, now take it down.

TunerMaxima3000

iTrader: (4)

I have to say, as I recall it, it's not a 'rattle' at all. Not at all.

IMO I remember it more as a Bearing whine, but only for a split second, as it 'winds up'.

As far as all this belt talk, just pull the damn belts and check the pulleys, you don't need a belt on there to check the pulleys or bearings, it will be fairly obvious if they're hurting at all.
.
I still think this is more of a whistle, and suspect air intake, or exhaust. There's a potential that it's something internal in the engine also.

Please correct me if I'm remembering the noise wrong, if I'm remembering it correctly, it sounds nothng like marbles being shaken in a tin can.

Clashez

iTrader: (5)

I have the mystery rattle to, but i only hear it when driving. if i'm reving it up i don't hear nothing up 70000rpm revs. i wonder if its the tranny

Rochester

iTrader: (3)

We both heard the same noise, but are describing it differently is all.

It's not the SRI. That's a much shorter, distinctive and fast little whistle that you can hear when you punch the throttle from idle.