Replace Frankenstein Bolt captive nut?

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Replace Frankenstein Bolt captive nut?

Postby 71NotOut » Mon Nov 09, 2015 11:36 am

My car came with no Frankenstein bolts, instead it has 4 blots that sit flush with the chrome trim.

The front one on the passenger side is loose, and further investigation shows that there is no nut/thread for it to screw into so it just turns.

I would like to resolve this to prevent any leak issues in the future, but looking at the underside from the boot it looks well hidden behind some metal trim.

Has anyone managed to get to the bottom side of these fixings?

Do I have to strip my boot down to get into it?

Strangely I found a spare nut sitting down by my jack yesterday and the thread fits that bolt so I guess I know where the nut went to!
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Re: Replace Frankenstein Bolt captive nut?

Postby gm » Mon Nov 09, 2015 12:37 pm

It is tricky but with the right combination of sockets and extensions, I managed it - although it was the drivers side on mine that had come loose. If I remember rightly, there should be a gasket on the underside of the plate and an O ring on each of the Frankenstein bolts. it may be worth putting a wee dob of silicon under the plate to keep it watertight.
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Re: Replace Frankenstein Bolt captive nut?

Postby mgrays » Mon Nov 09, 2015 2:05 pm

Fairly sure they are captive nuts i.e. welded into bodyshell.. maybe with a thin steel cauge to let the square nut float. The thin steel cages would be easy to damage and would easily corrode if you had a leak but everything I see and remember says they are welded solid nuts.

I had mine off to respray, also a Roadster and it was just a case of big Phillps blade screwdriver and ensure you do not damage the chrome... the threads have blue thread lock on them and so the O ring is not actually required as this blue gunk keeps the water out.. replace with silicon sealant at they are not under any load.

There is a gasket but it does little.. I guess with the O ring and the gasket it keeps the water out as the bolt holes are at the bottom of the indent for them.. it does cover the joint seam between 2 panels which is it's main function.

Franken bolts with O ring..
http://www.miataturbo.net/miata-parts-s ... lts-16609/
Removed parts
http://www.ctitech.com/users/rlcina/boltmiata2.jpg
http://treasurecoastmiata.com/images/F59516353.jpg
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