Introduction / Locating the Noise
This may be a subject that doesn't really require a write-up, but being a car noob myself just a few years ago, I figured some other noobs might like a page on how to eliminate all of the noises that their car can start making as it ages.
Finding the noise is actually the hard part a lot of times. Usually I find a nice bumpy local road that's quiet and go driving around slowly while pushing on various panels until the noise stops. For really difficult to locate noises, you can also enlist the help of a friend / spouse to drive the car while you try and figure out the source of the problem.
Once found, I generally quiet the panels using Dynamat that I've had left over from my various audio projects - though you can use any vibration dampening material that you wish.
Tips on Removing Plastic Panels
I always start with disconnecting the negative terminal on my battery. Most of the panels generally have some kind of wiring under them that needs to be detached. It only takes a minute to disconnect the battery and it can save you the headache of figuring out which fuse blew later.
Once that's done, onto removing the panel(s). Generally there are a few screws here and there and then the rest of the panel(s) is held on with plastic clips. You can buy some plastic panel tools online or at Harbor Freight, they will look kind of like this:
These are good for popping out plastic panels without marring anything. Though you will also find that your hands are just as useful. Sometimes it's easier to get your fingers behind a panel and just give it a fast yank. I say fast because you don't want to slowly pull any panels out as you will be more likely to break the clips. Just pull up/out straight and fast and you should be good.
One of the first annoying buzzes came from the latch for the top (though this may only be an issue for the PRHT or RHT).
This fix I can't take credit for - forum user Jim Dreiling is the one who came up with this, and I just copied his idea.
This plastic piece covering the latch comes from the factory without anything to hold it in place, and so it buzzes annoyingly almost from the start. So, as Jim Dreiling suggested, I used some door edge guard that you can get from any auto parts store and ran it around the top of the plastic piece, thereby pushing it against the roof and quieting it. To make it easier, this part will actually pop down a little bit, and in fact may even come completely off if you open the latch (I never tried this).
Most of the buzzing noises seemed to come from the coin holder piece at the front of the NC1. Though the entire center console and the back piece can also cause buzzing.
For the coin holder, I popped it out with a plastic panel tool inserted in the area right in front of the shifter. I then proceeded to Dynamat several areas underneath it.
As you can see, you don't have to be really picky with using Dynamat on it (obviously I'm not ), I just cut up little pieces and apply it. For the coin holder, you especially want to do the sides of it, as that's what will help hold it in tighter.
The back of the console piece doesn't generally buzz much, but while I was at it, I figured I would throw some Dynamat on it as well. This piece just pries up by using the plastic tool along the edge. You mainly want to focus on the front edge of it where it comes in contact with the rest of the center console.
After you remove those 2 pieces, you can then get to all of the screws. Then unscrew the shifter knob and you can take the center console off. Be careful when you pull it up, however, as your window switches are still connected. You'll have to reach in and disconnect them before you can completely get the console out.
I forgot to take pictures of the underneath of the center console part, but you can Dynamat as before, focusing on the two sides where it comes down over the carpet, as those seem to be the biggest noise-making areas of it.
This has both noise and audio ramifications. Bass notes are always going to sound bad until you Dynamat behind the black plastic piece on the door. It also has the added advantage of quieting the doors down. (Note - I borrowed most of this from my NC Bosectomy Wiki Page)
1) Remove the inner door card. There are many instructions for this on Miata.net so I won’t go over it again. 3 screws and then just give the door a yank from somewhere along the bottom for the plastic clips to come out. It’s a good idea to have at least 2 or 3 extra plastic clips in case one breaks (Mazda part # GJ6A-68-AB1).
2) In order to properly Dynamat we also have to remove the black plastic section. You’ll have to take out the woofer, then there are about fifteen 10 mm bolts and a couple of plastic clips that hold the black plastic piece on. After those are all removed you have to remove 3 cable connectors (see following pictures for the cable connectors removed).
3) Once you have every bolt removed and cable disconnected, you can now pull the plastic section off. The part around the speaker has some sticky foam on it, so you have to kind of pull / peel that off. You will not be able to remove the wire loom coming into the door, so you can just kind of rotate the whole thing around and sit it on the seat.
4) Now you should have a (mostly) bare door that you can apply Dynamat to. My door was a little dusty / dirty so I went ahead and wiped it down with some alcohol to help the Dynamat adhere.
5) I hung the Dynamat up with some blue painter’s tape to get an idea of where I needed to cut edges and holes. I used my fingernails to roughly mark where the holes were.
6) Then I removed it from the door and cut it with a utility knife on the driveway. Don’t worry if the holes aren’t quite big enough, as you can trim it after putting it back on the door. In fact, I’d recommend trimming a little less than you think is needed.
7) Time to peel and stick it to the door. I mainly focused on Dynamatting the part of the door that is behind the black plastic section, as this is the part that vibrates the most. You can do the upper part of the door as well if you’d like, however.
8) I also went ahead and put some extra Dynamat around the inside rim of the woofer area on the plastic piece.
9) Now comes the fun part. You have to go back and find all of the little holes for the bolts, plastic clips and wire connectors and cut the Dynamat around them. You can always hold the black plastic piece and / or the door card up to it to make sure you got all of them. There are also some larger bolts that hold on the window frame, so I cut holes around those as well in case I ever needed to get to them in the future.
Note: You may notice that I have some Dynamat inside the door behind the woofer. I did this during a prior installation, but found it didn’t really accomplish anything, so my recommendation is not to bother doing this at all. Just focus on Dynamatting the door area that sits behind the plastic section.
10) Now you can put the plastic section back on the door and bolt it all back up again.
11) Before you put everything back together, there is one other part that can cause vibrations - the little piece behind the interior door handle. Go ahead and Dynamat the back of this as otherwise it might start buzzing in the future.
After replacing my stereo, I started to get an annoying squeaking sound coming from my dashboard. After driving around and pushing on various parts, I discovered it came from the upper corners of the radio. So if you get this squeak, you'll want to slide the stereo out and put pieces of Dynamat underneath the corners of the dash panel (circled in red) to quiet it down. As others have documented how to remove the stereo in the NC, I won't go into details here. I've found that pulling the stereo in and out a few times until it really feels like you got it in there good and solid also helps.
The wind blocker was a more recent annoyance. The piece folds up and down, and appeared to have some foam stuck on the bottom of it from the factory, but apparently the foam eventually wears down and it starts to squeak / buzz.
As I never put this piece down, I went ahead and stuck unsightly Dynamat underneath it and just made sure the Dynamat was covered by the piece. If you do put yours down, you probably want to try something like black velcro or something more pleasing to the eye.
Windshield Header and A-Pillars
Once I had finally gotten everything else quieted, I started to notice the windshield header plastic would occasionally buzz. So it became the next area of attack.
1) You want to put the top down, as the header won't come out otherwise.
2) Then start by removing the Torx screws in the header (there are 6 total, 4 of which are T40, the other 2 I think are T30). When you remove the larger T40 ones, the metal plates that the top connects to will come off.
3) Once the Torx screws are all removed, you can then give the header a quick pull down and it's plastic clips should pull out. Careful when you do this, as there is a connector going into the header for the dome light. Disconnect the dome light wires and then the entire header will come out.
4) While I was working on the header, I figured it was a good time to do the A-pillars as well for preventative measures. They have no screws just pop them out to the side and then they slide up and out of the dashboard. Once I had them all out I laid them on a towel in my driveway so as not to scratch them.
5) I had a two-fold plan for the windshield header. One was the usual Dynamat, the other was to improve the clips a little. There are two sides to the clips, the bottom piece that attaches to the plastic, and the top piece that goes into the metal header. For the bottom piece I squished it a little more so it grabbed tighter to the plastic. For the top piece I expanded it out a bit with some needle nose pliers so it would hold better. Obviously you don't want to over-do either of these as the clip could break.
Prior to bending:
Prior to expanding:
6) From there I proceeded to Dynamatting the header, focusing on some of the edges where it would contact the metal.
7) Then I continued with the A-pillars. Since these panels have never made any noise (that I've noticed) I just did a general covering of Dynamat on them. You may not want to bother with this part until (or if it becomes) necessary.
8) Now time for re-assembly. Connect the dome light back up again, then snap the header back in place. Then slide the bottom of the A-pillars in and snap them back in place on the left and right.
9) You can tighten the smaller T30 Torx screws down, then put the metal plates back up with the T40 Torx screws. However leave the metal plates a little loose and move-able. We will need to put the top back up and make sure the pins go in nicely before we tighten those Torx screws down.
Now that you applied material to dampen the noises, time to go driving around the block again and duplicate the conditions of when it would squeak before. I usually do this with the top up and the radio off to really make sure I took care of it.
In the windshield header example I found that I didn't manage to get all of the vibrations like I wanted to. So I had to go back and apply Dynamat to the metal part of the header next in order to finally quiet it.
This process can be kind of trial and error like that. But eventually you will be rewarded with a squeak and noise free car - well minus the wind and road noise anyway