Ambiguous metallic rattle — passenger side

Technical Area Body, Interior & Styling
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  1. My model of MX-5 is: 1995
  2. I’m based in: Greece
  3. I’m looking for technical help or recommendations on: locating an ambiguous metallic rattle — passenger side

Hi everyone,

I’ve got a persistent rattle that’s been driving me crazy and I’m hoping someone might have an idea or two.

The sound: Best way I can describe it is two metal shards or shims vibrating and clinging together — almost like two pieces of sheet metal kissing at road frequency. It’s clearly metallic, not a bush or rubber sound. The sound is there with both the hood up and down. It is not like a small fastener or clip has fallen into the body structure, it’s more like a welding has come loose and the metal surfaces tap against each other.

Location: Seems to originate somewhere on the passenger side rear — the seatbelt/B-pillar area or along the rain rail area but on the non-visible side between the outer fender and the car body. It’s probably somewhere high in the body - think of it close/behind the rain rail.

What I’ve already done:

  • Replaced all bushings underneath the car. Also, the hood has been replaced at some point in time.
  • Checked the boot — antenna mechanism, spare tire - everything seems solid
  • I removed the passenger’s seat, rear deck carpets, the seat belt retractor mechanism, emptied the trunk completely. A few cables in the trunk were here and there and were tapping to metallic surfaces, but that wasn’t the problem. With these things removed a can hear the noise clearer.
  • My mechanic has been looking into it and tried using a sort of stethoscope and the noise seems to be somewhere in the non-visible area behind the rain rail/read fender but still can’t feel it/access it by hand, which would make it stop and we could locate it.

I noticed there are openings from the inside of the car to several cavities in the rear fender, but this is a place I can’t access (thinking of getting even an endoscope camera with a magnet and LED light but I fear that the movement of the metal will not be that visible).

I found the following pic and I’ve circled the suspect areas.

Screenshot-from-2026-04-22-08-48-35
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Has anyone faced something similar before? Any tips to access these areas or how I could spray some kind of “grease” that would make the noise milder?

2

Noise can travel, you think it’s from behind or in front or one side. Can I suggest looking to see if the heat shields are secure on the exhaust system. Pay particular attention to the heat shields on the down pipe and around the cat. I had this problem on my NA, the heat shield worked loose on the down pipe, a clamp secured it, no more metallic rattle.

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IMG_5664
IMG_56641920×883 414 KB

Ditto for the sound travelling. A loose plastic cap was humming and rattling constantly but while driving I was convinced it was coming from the passenger door. I think the noise was resonating up the sound pipe and was blending with a very light rattle on door lock. A small piece of inner tube as a shim stoped the lock button tapping which led me to investigating under the bonnet as the really bad rattle then seemed to be behind the dash. Luckily I jiggled everything and found the cap was really loose.
Now at low speed with the top down I can hear a drivers side metal on metal ting over potholes. I think it’s either exhaust bouncing on its hangers or brake shield slightly loose. I mention it as you may have either of those causes and just realised passenger side for you is opposite to mine. I mean left hand side looking from the front.

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I’ll ask again the mechanic to check. Thanks for pointing out and I will update you. This is driving me nuts even before a set the car to a standstill of almost 10 years…Now that I’m restoring it I’m just determined to fix this, it’s almost impossible for me to listen to this anymore.:face_with_symbols_on_mouth:

5

Have you put a different, perhaps larger exhaust on it? It could be vibrating on the chassis?

6

When I got my NBFL there were some strange rattles from the back, getting a battery well board to secure the jack handle properly made a huge difference as did putting the wheel spanner in a proper cloth bag. The real culprit though was a second wheel spanner that was hiding below the bolted down spare wheel. Later started getting rattles from the torsion springs that keep the boot open, that was down to keeping to much crap in the boot. Hope that helps, as others have said the heat shield above the back box is also problematic. Good luck with your search.