I viewed some online videos about this process and tried two different techniques; first technique involved the one I found online which uses a Dremel tool to cut the main body of the lens cover off the headlight housing leaving a 3/4 inch strip attached to the lens housing channel which is then removed using a heat gun and various poking and prying tools. This was a pain in the butt....I relied too much on the heating process to loosen the adhesive and although successful it was not a clean and error free process. So on the next headlight I tried something different that I'm excited to share.
My thought was to rely mostly on physical detachment of the adhesive from the plastic in the lens housing glue channel using an assortment of razors and knifes and use the heat on difficult spots. But I didn't even need to use the heat gun!
1. Remove headlight from car being extra careful detaching the plug wires from headlight. I actually used a plastic trim removal tool to pry the plug off so as not to damage the plastic plug body.
2. Gather these tools for the lens removal process; Dremel tool with 1 1/2 inch plastic cutoff wheel, flexible razor knife with the breakable segments, Dremel shaping/cutting drill bit, a pick tool with a 90 degree hook, a buck knife and some locking pliers.
3. Using the Dremel tool cut the lip off the part of the plastic lens that covers the glue channel in the housing. This will allow you to run the cutting tools, razor, pick and knife down into the channel alongside the lens plastic. Cut any nubs or clips off the lens that allow the housing clips to secure lens, they just get in the way so I carefully cut them off using a small Dremel cutting head.
4. So yeah this is dirty work (face mask is recommended), now using the plastic cutoff wheel go around the entire lens again this time cutting the entire lens cover off leaving a 3/4 to 1/2 inch strip of lens plastic ( which remains attached in the housing glue channel). Use a screw driver to pop off the lens cover. Note; there are three screws that attach some trim material to the lens, carefully cut around these screws, they will be removed from trim later.
5. The cut-off wheel does a lot of melting of plastic while you cut, but it does a great job. Trim any melted bits off the plastic strip that remains in the housing channel so razor knife and tools can more cleanly run down into the channel. So....go ahead and now run razor knife and the more study buck knife blade up and down the entire channel inner and outer edge. Occasionally run the pick tool down into the channel as well. Some adhesive will be pulled out. Do this again and again over and over, running the tools up and down inside and outside the glue channel alongside the plastic lens strip still stuck in channel.
6. I anticipated having to create a break in the plastic stip so I could grip it more easily with locking pliers, I used wire snips to cut a v shaped notch in the plastic. Turns out this wasn't necessary in my case because as I gripped the plastic with my locking pliers to start pulling the plastic strip out, IT JUST CAME RIGHT OUT ALL IN ONE PIECE! Why am I excited because the other lens I removed was way more difficult; when using the heat gun the strip came out in several pieces requiring a ton of pulling and tugging and distortion of housing tabs and channel!
7. Now using the razor knife and pick tool, clean the adhesive out of the channel. Get as much of the old adhesive out as you can. I found that by carefully running the razor knife along both inside edges of the channel I could remove quite a bit. I also used some rubbing alcohol with a q-tip to clean channel. You could try a better solvent but I didn't. IMPORTANT clean any bits of debris from housing before attaching lens, when I put in new bulbs bits of wire sheathing that were lying inside housing fell onto new lens surface!
8. Test fit the new lens cover in the headlight housing. If you need to, trim and plastic bits that don't align well. I found that in my case fitment was good but not perfect. In fact the black trim piece that had the three screws attached didn't screw in well and I had to use longer screws ( also the screw removal from the trim piece wasn't easy so be careful).
9. Press the new adhesive into the glue channel of the lens housing. I use a black butyl rope/tape. Using a heat gun I heated up the adhesive and then pressed the new lens cover into the housing channel. I had a half dozen metal clamps and placed them on the lens to housing joint, pressing the two parts together. I removed the rubber protection tips off the clamps to get them to stay in place. With clamps in place I went around with the heat gun to facilitate the adhering of the pieces.
10. Not sure if this part is necessary but I oven baked the entire headlight assembly to help the butyl adhesive do its job. I heated up the oven to 275 degrees and baked for 15 minutes. My clamps wouldn't fit in the oven with the headlight so I heated the assembly without clamps and then replaced them later while entire assembly cooled down. After 24 hours I installed headlight back into the car!!
I've included a few pictures to help my words above make sense. Wasn't planning on writing a procedure so this will have to do.
- Housing channel with adhesive residue
- Dremel plastic cut-off wheel
- close-up of the 1/2 inch lens strip removed
- tools and lens plastic strip removed