Disassembly of Tail Lights / Adhesive Question

[Oiluj]

Just finished taking my tail lights apart. I have one extra tail light and wanted to switch the less pitted chrome strip to the better assembly.

So here's a question for the pundits:

What type of adhesive was used to asemble the lens to the body?

(I like the fact that it can be removed by heating the joint in case I ever have to replace a lens...)

Disassembly of the lights was much easier than I thought it would be.

Just poured very hot tap water on joint betwen the lens and grey body. With a little gentle prying with a screwdriver, they came right apart. I did snap off the retainer in back on both trying to get it apart.

Then removed the chrome strips from the lenses got two of the 6 push nuts off without breaking the plastic pin, but I figured I'd have to glue them back on anyway.

Remaining adhesive was easliy removed from the lens with hot water and finger pressure. Adhesive left in the body channel was removed with hot water and a small screw driver.

[Seppi72]

I've never had a reason to try this myself, but from your narrative about the hot water loosening things, it sounds as though the assembly was put together with a thermoplastic adhesive - what would generally be called a hot-melt adhesive. There are dozens of hot-melt chemistries available these days, but one that might be good for reassembly and water-tightness would be the terpene-modified types. These are similar to the adhesives used to hold inserts onto magazine pages. They are very rubbery and water-resistant.

The thing is that these materials usually aren't generally availale to the public because they need specialized equipment (computer-controlled and F-A-S-T) to be best used. You might try experimenting with some of the commercial hot-melts recommended for use with cloth and leather, but that tail light case is pretty big.

A better option - although not thermolastic - might be to use a moisture-cured silicone sealant. They provide a long "open time" so you can get things applied, aligned, and clamped (if needed) before the adhesive cures.

[Darrel]

I always thought it was butyl holding the lenses on. They still used it on a '97 altima rear taillight.

[Seppi72]

Butyl is a tried and true adhesive used throughout lots of autos - both then and now - so it's a likely answer. As I said, I have never taken any rear light assemblies apart. I was basing my reply on Julio's report that the adhesive softened substantially upon the application of very hot water. Butyl shouldn't do that; especially after 30+ years. It should be almost rock-hard by now and unaffected by such "mild" conditions (almost boiling water is fairly mild by chemistry standards).

BTW, Darrel, the spindle pin remover still works fine. I just used it last weekend when I finally got my '72 onto it rotisserie. Slick as a whistle, pal.

[Darrel]

Bob,

Glad the puller is still doing it's job.

I have seen butyl get rock hard, but it's more of a hard shell from the dirt it developes to protect the rest of the material underneith. Either way it's good to know that taking your time and using hot water makes it a bit easier to disassemble the old taillights.

When I was sent out a new taillight for my altima, along with the lense they sent a small roll of butyl to seal it. Since it was a fairly new car at the time, it didn't take much to pry off the old lense.

[Zs-ondabrain]

I get the lenses up to room temp, then s-l-o-w-l-y pry them up and apart but not before removing the locking washer on the back. I've torn more than 30 pairs apart because I do the LED conversion to the 240Z taillights.

I try and leave as much glue as possible IN the rear assembly, then use a small torch to reheat it before reattaching the lenses. If I'm not able to retain the original glue apon removal, I'll go ahead and remove the rest with a flathead and then I use the Black 3M StripCaulk in the channel, heat it up then reattach the lenses that way. For reinforcement, I drill a small hole in the chrome after removing the plastic tab, then run a small skinny bolt all the way thru to the back and bolt it down.

Dave.

The pics below will show some of the process. Also, the third picture, you can barely see the phillips head screw in the middle of the trim and the last picture shows that bolt on the inside of the lense. It goes thru the back and gets a nut to tighten it down. And the second picture shows the reflector that I instal into the reverse light area as they never came stock with one.