Having worked in the business during the time when C3's were the most common customer's car, I can tell you that I got lucky more than not by, first, putting just a few of drops of penetrant around the head of the screw so that it run down the threads of the screw but NOT getting the wellnut all wet.
Let it sit an hour or so, and then "gently" pull up on the rack near the screw so that the well nut gets more friction where it meets the fiberglass hole.
Then work the screw back and forth to try to get it to break loose with the wellnut still gripping the hole.
There is a tendency to pull up harder and harder, but don't.
You really only need to get the screw to undo a couple or three turns before the nut will relax enough to come up through the hole with the screw still in it.
In fact, the way I reinstall the racks is to assemble all the screws through the rack and run the nuts up to where they barely touch the rack (without letting them compress).
Then it's a piece of cake to line it up and drop all the nuts into the holes at the same time and then snug up the screws.
When reinstalling, resist the temptation to over tighten the screws. Doing so can lead to cracking the fiberglass around the holes (over time).
Just a couple or three turns is all you need to secure it as well as it needs to be.
|UPDATED|11/2/2018 7:38:19 AM (AZT)|/UPDATED|