S4 - Bolt through rear underbody

[Gorpon73]

Hi,

Anyone possibly tell me what the bolt is protruding from the underside of the right rear body? I see most cars with this having a washer and nut affixed to this bolt on the outside of the body. Having trouble finding this in my manual and not keen to pull my fuel tank to discover what it is for?

Cheers

[seriouslylotus]

Fuel tank fixing....

[MarkDa]

+1 to fuel tank.
I put a dome nut on it to smarten it up a bit

[Gorpon73]

Fabulous, thanks!

Possibly know the thread pattern for this bolt? Nothing I have around seems to fit....

Cheers, DJS

[MarkDa]

1/4" probably unc if I remember correctly.
I fear I may have cut to length and cross threaded a 6mm dome nut onto it as I view it as a "one time" fixing.

[Gorpon73]

Haha. Sound logic from where I'm standing. Thanks for the info.

Cheers.

[Pastapesto]

Not sure but I think it's an UNF thread & not UNC......I'll check later & if I'm wrong.

If it has a non original tank then there is the chance it is something else of course.

Hope that helps

Adam

[Gorpon73]

OK, thanks for the info.

I've tried everything I had in my various piles, but nothing fit yet.

Looks to be a very narrow thread....

[MarkDa]

Could be 6mm?
Do you have a diameter and thread pitch?

[oldelanman]

If your fuel tank is original it will definitely be 1/4" UNF as stated above (just checked mine to be sure) but if it's a replacement tank it could be anything and as Mark says you will have to measure it. Could it be that your thread is corroded or gummed up if the nut has been missing for a while and just needs cleaning up ?

[MarkDa]

Yes - a bit of oil and then hand run a 1/4 unf die down it ought to do the trick to get it operational.

[oldelanman]

Yes - a bit of oil and then hand run a 1/4 unf die down it ought to do the trick to get it operational.

Or ... if you don't have a die you can just use a nut with a saw cut at right angles to the thread, works just as well.

[Gorpon73]

Thanks for the advice.

It's a 1/4-28. Got it all stitched up....

Cheers

[MarkDa]

Well done - yes that's standard unf.