stangalator

Alright I had an issue about 6 months ago with two cracks in each fog light. One on the top and one on the bottom. I could tell because there is condensation on the inside of the fog lights and the lights burn out within a few months... I figure, ha HA, cleaver me. I'll JB epoxy the cracks so the light seals out the moisture. Well here they are 6 months later and they are cracked again!! I'm use the standard 37.5W 899 bulbs too... what should i seal the cracks with?

MineralGrey

^ I would first try to figure out what the hell is causing that to crack lol, how much heat does one of those bulbs produce 38W? once the JB weld dries does it become brittle or it still flexible, how does it hold with heat (i have no personal experience with it). Also that looks like that housing has been cooking by the brownish color, or is that just the jb? I would use something that has alot more give so when the plastic is expanding and contracting it can keep with change, like a plastic epoxy sealant or something.

stangalator

^i agree, the jb weld turned brown from being cooked. It probably became brittle from all the heat cycles and finally cracked.


after a bit of research the JB weld is only good to 500 degrees F continuous and 600 for a peak. A common halogen bulb can get to 500-550 F on its surface. I use these as my "driving lights" whenever I drive the car they are on, so the heat cycles of room temperature to 550 F every day probably cracked the JB weld...

So does anyone have any ideas for a sealant that is water prof that protects past 600 F? I'm truly surprised that the jb weld didn't hold better I use to think that stuff was indestructible, haha.

MU71L4710N

i would try some high temp RTV. home depot, lowes, ace, oreillys, autozone, anywhere like that should have some. it doesnt dry hard like jb weld does so it should be much more resistant to cracking.

stangalator

I'm trying some rtv high temp now, going to let it dry for a few days just incase. It has about the same range of temperature as jb weld but I hope the extra flex will keep it from breaking. I also bought 880 bulbs instead of new 899 ones, the difference is the wattage is decreased from 37.5 to 27 watts, since the 37.5 watts suck for lighting anyways and they are purely for show i figured it would reduce the internal temperature without loosing much light.

ctgreddy

i doubt the actual casing would get up to 500+ degrees. i'm guessing the only reason it actually cracked again was due to the jb not having any flex. i actually was having issues with bulbs burning out on one side, and the one fog light was also a lot darker than the other side, so i pulled it out yesterday after seeing this thread and sure enough it was cracked in the same spot yours are. luckily i had a spare tho that i found in the attic, so we'll see how long before this one cracks lol.

stangalator

I thought that too at first, seemed odd that it would get that high temperature. I bet it was near 400 area though and near its max temperature because it burned a little, all four areas have a brown burn mark. Either way, im hoping the 880 bulb will be better with its lower wattage.