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Been trying to track down the source of my 'new' 3100rpm rattle. It's not the top head shield, nor is it the cat, or rear muffler. Which makes me think it's somewhere between the top part of the factory header and the cat.

Had a poke around tonight and there looks to be a big clamp thing just sitting there. Should this have a bolt through it to clamp the tin tight? Does it mount to something? What is it? Could this be causing the rattle?

It's this rusty thing here: (note, just a pic I found on the www, headers still on the car)



Many thanks in advance for your help guys.

Nath

Isn't that supposed to bolt to the side of the transmission?


(image \"borrowed\" from miata.net)

As Mr Q, pointed out it is supposed to bolt to a bracket that is mounted on the side of the transmission bell housing. The long bolt and nut can work their way loose. When I was installing the exhaust for my turbo I found that the bolt was ready to fall off. I had to remove it and the bracket to fit my new exhaust.

J

Thanks guys!

Just had a look again and it seems that I don't even have the bracket that mounts to the gearbox

Which also probably explains why I've had trouble with exhaust rattles since day one of ownership.

Mr Q, does mania have any sitting around in their NA box of bits and pieces?

Cheers,

Nath

nath wrote:Mr Q, does mania have any sitting around in their NA box of bits and pieces?

More than likely - although they're usually attached to the transmission. I'll take a look tomorrow.

Can the rusty ring thing on yours be removed? Most aftermarket headers don't bolt on to the transmission and don't rattle either - perhaps it's just the rusty bit rattling around that's causing all the noise.

Thanks Mr Q,

Not too sure if it can come off. And if it could I think I would cause more noises as the tin shielding looks like it needs to be clamped to stop vibrating. I just went out to buy a bolt and when the exhaust cools down I'll see if just tightening up the clamp solves my problems.

If you could still look for me that would be great. I have tomorrow off so might give you a call or pop in on my way past.

Thanks,

Nathan

Just had another look. Some nob has actually welded the clamp to the exhaust in the wrong position. Which means it will be a pain to get off... plus I can't tighten it due to the welds.

Ok, so I just put a new engine pipe on today - thanks Andre and Simone - but the noise is still there..... and getting worse

So it's not the engine pipe or heat shields....

I guess the game of 'process of elimination' starts now

There's a lot of places this rattle could come from. The main cause is the \"harmonic disharmony\" that the engine puts out at these revs.

You could try:

1/ All heat shields along the exhaust. I mean the ones above the muffler etc, and attached to the midpipe.
2/ The straps connecting the loom to the power plant frame.
3/ Possible gearbox, clutch noise
4/ Remove the header heat shield
5/ Check the alternator bolts. I had a bolt snap twice and caused a big rattle.

Actually get a rubber mallet and give all areas of the exhaust a good tap to see if you can replicate the noise.

Does it do it in neutral, or just in gear? This coud be a clue.
In respect to that clamp you just looked at, I used a U-Bolt to clamp it nice and tight. Mine used to make a bit of a noise. There is also from memory some \"tangs\" of steel that point upwards from this area that can be bent outwards if they are being noisy.

Good luck. Hope you track it down before it drives you insane.

Jules

Thanks for the tips Jules!

Ok, after looking at it for the last two nights, I think I might have found the problem.

1) Took off all the heatshielding - still makes a noise.

2) Unbolted the exhaust from headers - seems like noise is gone, hard to really tell due to loudness (and obviously now sounds like a boat)

3) Put car up on ramps, had brother raise revs till it made the noise - seems to be coming from the back. However, the exhaust really vibrates at the RPM range in question. Is this normal?

4) Bolted cat back on - noise seems to still be gone

5) Unbolted mid pipe from rear muffler, and shook it around. Rattles. Have a peek inside it with a torch to see part of the baffle missing. However, only a small part, about the size of a small hex nut. The rattle sounds like it's this size too.

So could this be the cause of the noise??? I mean, it's loud. Can something this small cause such a racket?

I'm going to put on my old standard exhaust this weekend and see if it goes away. I think only then will I be content in my search.

If indeed it does turn out to be the muffler there will be blowups. This will be the 5th time since getting it done in January I have had to take the exhaust back to get fixed. Thinking this time I might just ask for my money back.

I'm really, really getting sick of these exhaust shinanigans!

nath wrote:I'm going to put on my old standard exhaust this weekend and see if it goes away. I think only then will I be content in my search.

If indeed it does turn out to be the muffler there will be blowups. This will be the 5th time since getting it done in January I have had to take the exhaust back to get fixed.

So all this noise started after fitting an aftermarket exhaust or was it there prior to that?

Was it a cat back system or just a rear muffler?

nath wrote:
3) Put car up on ramps, had brother raise revs till it made the noise - seems to be coming from the back. However, the exhaust really vibrates at the RPM range in question. Is this normal?

>>>I would say so. The whole engine vibrates at these revs. That's the "hamonic" I spoke of. If you ever get rattles, it is usually because of this.

nath wrote:So could this be the cause of the noise??? I mean, it's loud. Can something this small cause such a racket?

>>>There's 3 possible answers to this question. YES, YES and YES.

I think you have found the cause. Can you remove the debris and try the mid pipe out??

Jules

Good effort by the way!

JBT wrote:So all this noise started after fitting an aftermarket exhaust or was it there prior to that?

Was it a cat back system or just a rear muffler?

Nah JBT, I originally had a bit of a rattle which dissapeared when I fitted a new cat-back exhaust and hi flow cat at the beginning of the year. The exhaust place managed to stuff up the new system 4 times by either making it sit too low, crushing the pipe bends, making it rub against the transmission, dodgey welds (like filling up a 1inch gap by just welding it) and then issues such as baffles breaking inside the rear muffler section. I thought that finally I was free from all of this, as it has been fine for the last couple of months.

Jules, I can't remove the loose debris that's inside of it unfortunately.... If I could I would, and then not bother with the exhaust guys... I have a feeling that I'll be opening up a can of worms going back there again.

Best plan of attack is going to try and ask for a refund on the basis that I've been back so many times (and the place is a good hr from where I live - I've gone through about $100 worth of petrol and tolls already!) and then use the money to fund an SP motorsport cat back exhaust.

Fingers crossed : )

N

I'd love an SP motorsport cat back exhaust. Just can't justify it....yet.
Then again I've set a period of 3-12 months before I'm in a factory Turbo. I've never had a loan for any car, and am not about to start now, so maybe the standard exhaust can stay on a bit longer


Jules

nath wrote:The exhaust place managed to stuff up the new system 4 times by either making it sit too low, crushing the pipe bends, making it rub against the transmission, dodgey welds (like filling up a 1inch gap by just welding it) and then issues such as baffles breaking inside the rear muffler section.

Oh well, it's not surprising that a loose/broken muffler baffle is the source of the rattle then. They can make a heck of a din under the right conditions. Good luck with the refund.