Seal Headlights Like a Pro
Get a good quality Butyl sealant such as OCI, or even better Morimoto RetroRubber. I was using OCI until the RetroRubber came out, and it’s a much better product for sealing headlights. OCI works alright, but is made for windshields and doesn’t dry the way RetroRubber does. It stays kind of gummy. When RetroRubber dries, it’s more rubbery and was designed specifically with headlights in mind.
Re-sealing is much easier than removing. You need an oven, heat gun, flat head screwdriver, heat-proof gloves, and lots of clamps.
Some information about condensation. Condensation isn’t necessarily caused by a bad seal. It happens because there is warmer air on the inside of the light than on the outside of the light. If the headlight is just getting a little moisture on the lens you can add vents and cover with 3M Goretex patches.
If you actually see water pooling or large droplets, you might have a leak and need to try again.
Set oven to 240F.
Smooth out the old butyl glue if not removing it. I use a heat gun to warm it a little and a flat-head screwdriver to smooth it in the channel.
Add a string of new butyl or retrorubber to the channel. Stretch it out so that it’s thin, because too much butyl will prevent the lens from seating deep enough into the channel.
Push the lens in place until it sticks on its own.
When the oven is heated, put the lights on a baking sheet, grill protector sheet (I use Yoshi’s from Bed, Bath, and Beyond), or damp towel so that no metal in the oven is touching any plastic on the housing. Set a timer (I always set 2) for 10-15 minutes.
Use some thick gloves to get the light out of the oven and push the lens in as far as possible.
Start clamping the edges. Add clamps wherever you possibly can. The more the better. Good time to reinstall any screws or clips that help keep the headlight lens in place as well. Wait for it to cool down, and it’s good to go.