Every single 240 '86 and newer I have owned, the headlight covers always come loose and dirt gets behind the lense. Superglue crazes the plastic lense and I don't want to use epoxy. I stumbled across a solution one evening by using small rubber weatherstripping and clips(4) used on the 740 cigarrette lighter bulb housing. It's a nice solid waterproof fix and I can take the lenses off every once in a while to clean them.

Well, OK, but the bead of original adhesive can be removed with an awl, and there is a good tongue and groove which can be re-sealed with Goop. I like your method, but the putty-gunk is probably still in there, right?

I have never seen any glue on my lense assemblies leading me to believe they just heat welded them together and over time they fail.

Look harder, it is like tan window putty. You probably don't see the deep groove in the housing (rear). You need to gouge it out with an awl and you will see how they built these. That is all I have to say on this.

For the weathersripping, go to your nearest mom & pop hardware store and ask for door weatherstripping inserts or window screen line ( used to fasten the screen to the frame.) Start at the bottom and work the weatherstripping around the housing until it meets itself at bottom, then cut 1/16 short to allow drainage at the bottom. Do not stretch the weatherstripping as you work it around or it will shrink back leaving a big gap at the bottom. You may have to scrape glue out of the channel of the housing but I haven't had to.