jon928se

If there is a 1% chance that it needs to come out again don't use superglue because contrary to my expectations it will stick permanently

On the other hand if you 100% certain that it never ever ever needs to come out again you can use superglue until you are blue in the face and it won't stick.

I have only ever succesfully stuck two things with superglue. 928 Brake pad wear sensors to brake pads - you know when the flanges on the new sensors fall off as you insert them into the brake pad. and Nitrile rubber shop gloves to greasy CV joint boots (by accident and not on a 928). I've deliberately tried to glue my fingers together and failed.

worf928

Black RTV works well (ok at least) to seal up the filler neck. New filler necks need to be checked that they are correctly sealed from the factory. Find the seams and wiggle parts to make sure they are secure. If not you pull them apart and reseal with black RTV.

One guess, and one guess only, as to how I know this to be true with new filler necks.

the flyin' scotsman

You installed a NEW filler neck and it failed shortly there after?

worf928

Like I said - one guess

I converted my '89 to the GTS breather system which requires a GTS filler neck. A day or three later I hopped into the car and drove to Frenzy and back only to discover the front of the motor covered in oil - coming from the top seam in the neck.

After discussing the issue with one of the big three we determined that the new filler necks (at least the GTS variety) have a very high rate of infant mortality because they are not properly sealed at the seams. (On-the-shelf necks showed the same failure at the top seam.)

In this case all I had to do was to pull the head out of the neck, degrease everything, and reseal with RTV. So far - couple hundred miles - so good.

So, check the seams.