I think I found My Rattle - How The Heck Do I Secure This Thing???

[choinga]

So, I've got one of those low end frequency sort of rattles. Not so obnoxiously loud that it drives you crazy - but just loud enough that you notice it, which is almost worse.

Anyway, it was hard to diagnose by myself since it really didn't do it at idle and even goosing it a bit wouldn't make it kick in. When I'd drive though as I was in low gear and took my foot off the gas as I was slowing down...I'd start to hear the rattle.

I had another heat shield that only had one screw (of 3) holding it on and was missing the bolts coming out just to the left off where this picture is, so I just took the other screw off and pulled the shield down. I'm not sure how much of a problem that one was - it seemed a bit quieter when I took for a quick test run after removing it.

This one though - I don't know what to do with. It's some kinda metal flange thing over the exhaust that's welded around all sides. It's loosey goosey on there and rattles like hell. I got a small hammer out and tried to press it down with my hands as hard as I could against the bottom and then hammer it a bit to get it to stay - but no luck. Just tapping with the hammer on the other side knocks it right back out.

Some white power crap comes out when tapping on it - not sure what that is...

Anyway, any thoughts on what to do with this thing? Is there any way I can secure it??

[DSPTurtle]

From the look of the bottom of your car in the pic, it appears that you take really good care of it so just beating the cover tight against the pipes may not be the answer you want. If you are so inclined, you can take that crossover pipe off and weld it back on there correctly. The quickest way to go is to probably take it to a local muffler shop and have it tack welded in a few spots to keep it from rattling. I think that sheetmetal wraps all the way around the pipe so you would have to cut it to take it off. I am guessing $25 at your local shop should do it. But then again, taking the whole thing apart and being able to assess the situation is priceless and probably much more pricey Once you have to replace the gaskets stripped nuts and broken bolts of course.

[choinga]

So, I fixed the main rattle (Thanks JB - went to Midas and they put two spot welds on there for free...) but still have one coming from the rear of the car. I can't find anything loose back there but, well hear it for yourself...it's a very small mp3 file...

Basically, if I rev it up in first or 2nd gear and then just let off the gas I get this noise. It's sort of in time with engine an doesn't sound like metal banging around - almost like gears...

It doesn't make the noise during acceleration or when it's sitting still so it's very hard to figure out exactly where this is coming from.

Any ideas??

MVI_0240.mp3


(Scroll down to where it says download using basic to download the file)

[mikepellegrini]

Jeeze your car looks great! That's gotta be the cleanest underside I've seen in one heck of a long time...

[choinga]

Originally Posted by mikepellegrini

Jeeze your car looks great! That's gotta be the cleanest underside I've seen in one heck of a long time...

Thanks - this stuff is the bomb:

http://www.detailedimage.com/Chemical-Guys-M31/Grime-Reaper-P180/

I diluted it a bit and used my power washers soaking nozzle to get it all up underneath there and let it set for about 10 minutes then power washed it down. Just jacked the car up on either side until the wheels came off the ground and that was all the space I needed to get the washer hose under there and clean it up.

That Grime Reaper is really, really good though. Best I've used. Believe me, when I got the car it looked nothing like that. I bought that stuff after I changed my oil the first time last week and had guck all over me from under there.

[DSPTurtle]

Silly question, but since you said you just got the car... have you checked to make sure there is fluid in the transmission? Open the fill plug at the top and stick your finger in. It could be that simple if your "gears" diagnosis is right on. Also, check the motor mounts... they could be letting the engine move around and things touch each other that shoudl not be touching. I had a BMW that kept mysteriously shedding an upper radiator hose and making it clack against the fan. Could not figure it out for the life of me till one day, by luck, I was jacking the front of the car under the oil pan and realized the engine was moving way too much in relation to the car.
Two other checks... CV joint bolts (in the back attaching the tranny to the rear wheel), both inner and outer. Don't try to over torque them or anything, jsut see if they are loose. And, I am assuming this is a turbo??? Correct me if that is wrong!!! But, snapping the throttle shut after acceleration will cause a boost spike, which will cause the wastegate to open and close. That could be the noise you are hearing and not used to... your recording, while a good try, is nowhere near being able to really hear anything Not being mean, just honest!!!

[choinga]

Thanks DSP - I did my best with the audio.

I thought it might be the mounts but the PO just changed them (and used the good ones) a few years ago. It also NEVER does this at any other time. If I'm in 3rd and crusing and goose it - nothing. It's only when I'm slowing down in 1st and 2nd and let my foot off the gas it shows up. I think at some point I'm going to go with a Tial wastegate, but right now that's not the problem. No noise from there, boost is good and I don't think that's the issue.

I'll check the other things though for sure - I'm going to pick up some Redline fluids tonight and will drain and fill tomorrow and see if that does anything (checking out the quality of what comes out first of course for any problems...). The boots and CV's look good - no problems there that I can tell.

[DSPTurtle]

Choinga,
With all of the other issues you have had with the exhaust and shields and such, I would not be so quick to move on to other items as the potential problem. There is a shield that is above the catalytic converter (almost under the shift knob) that also has a tendency to rattle against either the body or the pipe. This produces a really weird rattle frequency that comes and goes. Mine was only on full throttle through a left hand turn... figure that one out when you have time. I bent and beat that little bastard ten different times before I finally got it to a place that is in tune with the Porsche Universe. I was gonna take it totally off, but decided that would probably cook my butt so I just kept playing with it.
Back to the WG though... I don't think it is a problem with the WG, no tial required, but rather the tubing that recirculates the exhaust back into the system. If you have a leak in the tubing or gaskets leading from the WG to wherever it dumps, it could make a racket everytime it opens. You may notice it more under decel since the engine itself is not making any on power noise. Although, from what I could hear on the recording, it sounded a lot like a J-Brake on a diesel truck... again, exhaust related. I guess my next question would be how long the noise emanates after you snap the throttle closed. Is it more then a second or two? On my 930 turbo I took the WG muffler off so every time it opens it lets everyone know I am back in town. God only knows with the PO's have done to your car and whether or not it is still bone stock. I actually cut my WG muffler open, removed the gut and welded it back together so no one would be the wiser

[choinga]

Thanks again DSP.

I don't have a cat - so it's definitely not that.

You could very well be right on it being an exhaust issue - but I don't think so. It's sounds like gears - not an exhaust frequency. If I'm sitting in neutral and floor it - the noise doesn't happen. I don't know any other way to replicate where I can get under the car and listen closer because it never happens when I'm sitting still.

[Techno Duck]

Just a note, the white powder that comes out when you tap on the crossover is asbestos insulation! Be careful.

[choinga]

Originally Posted by Techno Duck

Just a note, the white powder that comes out when you tap on the crossover is asbestos insulation! Be careful.

Sweet...i had that on my shirt for the rest of the day...

[lupin..the..3rd]

Originally Posted by choinga

Sweet...i had that on my shirt for the rest of the day...

You can get a nice buzz if you snort it.

[danphoto]

I've got the same problem with my S2. I have it on initial load if I accelerate hard before it gets on the cam and it's constantly there when trailing the throttle. It's been driving me crazy. It's really obnoxious when the tranny gets warmed up. It's competing with the exhaust and getting to the point of being embarrassing. I've also got the rattle in neutral with the clutch out. I'd love to know what is going on.

[kdjones2000]

The "Rattle in neutral with the clutch out" is inherent in these cars. There was a Por$che bulletin about the clearances on the Fifth gear being larger than the others, causing the rattle. They declined to call it a "Fault", so you are stuck with it.

I get a rattle right around 2900 RPM, accelerating or decelerating. I have traced it to that stupid monster heat shield between the exhaust manifolds and the oil cooler plate. That thing is leveraged out so far on 2 flimsy bolts that it goes crazy when it reaches its harmonic frequency.

Maybe yours is something similar....

Keith

[danphoto]

Thanks Keith.

It's going up on the hoist Monday. I really need to try to diagnose the problem, I'll make sure to check it out. Much appreciated.

Daniel

[danphoto]

OK, after a good old looking over we (well it was Casey at Bill Mitchell's Eurasian Auto not me) traced the noise to the rear section of the transmission and he thinks it may be the reverse idler gear making all that noise as it's going along for the ride. I was really hoping for a heat shield or cat to be the culprit. Any thoughts? It sounds similar to choinga's sound clip. I'll get a sound clip posted soon.

[TSNAPCRACKLEPOP]

I didn't get to listen, but I have reduced some rattles by cramming a wad of tinfoil around and inside some guards/covers in the past.

[choinga]

Actually, the 'rattle' in my mp3 is really my transaxle - it's not anything rattling around it's the gear box. It's probably the same thing as yours if it sounds the same. I really only hear it when I'm in 1st or 2nd and take my foot off the gas and coast. If I disengage the clutch, it goes away.

FWIW, I went to Meineke and had them tack weld that piece on - took a couple shots on it and it's fine. Of course, now there's a new rattle up in the front and I can't find it...

[danphoto]

Yep, sounds the same as mine. We went over everything including all the heat shields, cat, muffler, the works. The sound is ot brilliant in the clip but you can hear it when the revs drop.

http://www.youtube.com/watch?v=Ug7uxeilHyk

[choinga]

LOL - yeah, I got that one too... Any idea if it's doing any damage?? What do you have to do to fix noisy gearboxes?

I just started to notice that mine makes that noise when I disengage the clutch when parked. Damn, these cars are noisy...