You asked the question rhetorically if these tanks crack. I don't know, however, my 86.5 smells really bad if I fill more than 14 gallons. My father took it to his Porsche dealer and they "tightened" some fittings, charged several hundred and the problem never went away. I knew I needed to fix it myself which I prefer anyway. I read your post about changing the fuel sender O ring and ordered one hoping that is the problem. Received it yesterday. However, I recall one time I filled the car and looked underneath and fuel was spilling out. Since then, I've been careful not to overfill. Every once in a while I forget but it hasn't spewed fuel like that since. I really think I have a cracked tank also. Not in the mood to spend several hundred on another tank, so I really hope the O ring fixes the issue. I'll post the results in case the crack is a common issue with these tanks.

BTW, I love reading your procedures. They are just fantastic and really help a novice like myself feel like an ASE!

Pretty much the same here, smell and dripping fuel if filled to the top; dripping stops after driving a bit.

Suspects: breather hose/cracked breather hose fittings/crack in tank similar to Dwayne/fuel sender seaL.

I took the tank out using Dwayne's guide - most like culprit, slightly folded-over sender seal that also caused the sender to rub against the tank splash well. As my car is in an advanced state of undress I can't tell you if the new seal worked even though it seems logical.

My tank was covered in liquid run stains/trails that didn't help. I put some fuel in the tank and moved it all around to see if the top of the tank had a leak - nothing.

How is the flexible fuel return hose at the toop of the tank? Clamped at the tank, crimped at the pipe end.

I'd bet our vendors carry them, but ...
Just because I once went nuts trying to find anti-vibration mounts for a Jaguar, just like those shown in Dwayne's second post at the pump and filter:

http://www.vibrationmounts.com/

Oaros - I replaced my oring this weekend following Dwayne's guide. Went very smoothly but like you mine is so undressed, I can't tell if the smell stopped. It seems reduced at least

The oring replacement worked for me! My wife is so happy the garage doesn't smell anymore. Thanks a bunch, Dwayne.

That's great news! Glad it was a simple fix - Enjoy!

so there is hope for mine which ponged at both ends before I started taking bits off.
Cheers!

My o-ring looked to be in good shape, so I was surprised it made such a difference in smell. Hope yours works too.:D