mx5cartalk.com

When I went to bolt the seat back in, the thread on the other side of the floor for one of the bolts dropped off. Can somebody tell me the fix please.

On the NA8 at least (& IIRC NA6 was the same) the front seat bolts screw into captive nuts in a boxed section. So seat will need to come out again if reinstalled & carpet will need to be lifted to allow visibility of the area to gauge accessibility. Check the condition of boxed section metal in the vicinity of the bolt hole for damage which might have allowed the captive nut to escape. If all good, it might be possible to manoeuvre the nut into the correct position with a knitting needle & magnet.

As above, you may be able to use a magnet etc to shift it, but even then you'll likely not be able to properly torque it down without the nut just spinning.


The most common solutions are to either cut the welds and remove the seat hump, weld the nut back into place, then weld the seat hump back to the floor.

Or, for a simpler option, people have also used rivnuts.
https://en.wikipedia.org/wiki/Rivet_nut

These allow you to make a captive nut without needing to access the back of the panel.

Rivnut would be ideal but I'm thinking if it actually needs to be strong (I think so). I don't know if the rivnut mounting offers that much strength. It is a seat mounting so safety is paramount.

Thanks for the practical solution khs_kansei. And the sensible caution Bruce. I was about to buy a rivet nut kt, but now I'll wait for an engineer to weigh in.

This article supports Bruce's caution: http://www.autospeed.com/cms/article.ht ... s&A=113110.

Have you pulled the carpet and checked the state of the floor and the other seat mounts? I had a bolt come loose on my NA and when I checked I had rust under the carpet and most of the mounts on both sides were suss. I took the car to a crash repairer and for a couple hundred bucks or so they fabricated new mounts and treated/painted the floor. Safe and peace of mind for a few $$$ ...

Sent from my SM-G930F using Tapatalk

From the above article;
I’ve seen seat brackets bolted to rivnuts inserted through the car’s floor panel: this is dangerously stupid.

KevGoat wrote:Have you pulled the carpet and checked the state of the floor and the other seat mounts? I had a bolt come loose on my NA and when I checked I had rust under the carpet and most of the mounts on both sides were suss. I took the car to a crash repairer and for a couple hundred bucks or so they fabricated new mounts and treated/painted the floor. Safe and peace of mind for a few $$$ ...

Sent from my SM-G930F using Tapatalk

This.

Even if it's not rusted I'd still give it to a panelbeater to do a proper job of welding in a new nut and re-rustproofing it for you. I don't think amateur welding skills and seat mounts go together very well.

Ah, I'm glad I didn't do anything quickly - I have gone from trying to fish it out, to using a blind rivet nut myself, to taking it to ACDC, and now probably to a panelbeater. Thanks guys.

I realised later that my last post may have sounded sarcastic. It wasn't meant that way - I am appreciative of the help, leading me to the right solution, saving me from doing something ineffective or dangerous.