I recently noticed some moisture in the corners of my headlights by the fog lamps. Being an 2004 TL with 205K miles, I thought attempting to add some desiccant and trying to avoid the purchase of new assemblies would be prudent. I bought some small packs off of amazon and got to work. In addition, I purchased new headlight gaskets (HID cover, control unit, and fog light). When I removed the HID bulb cover, I was pleasantly surprised to to see a large factory desiccant bag placed on the side. The bags have their own brackets to hold them in place. The contents in both bags were quite solidified, so I left them to avoid busting them open in my headlight. So far I have not noticed any moisture and encourage anyone with moisture to attempt this before baking or purchasing new assemblies. By the way, a question for the experts. Directly below the turn signals, I found a black rubber cap. After removing this cap, I found a rubber cylinder with what appeared to be a filter covering a plastic pipe with a hole running into the headlight. Could someone explain this to me? Is it an air inlet? Should I keep the rubber cap off? The cap had some spacers at the end where it meets the filter. Thanks.

 

leave the cap on it a breather valve