Silicone is used on servos and other cracks that water might find its way into. It works great on wires that come out of servos, recieves and other electronics. Some guys even take small ballons and fit there reciever in it so that no water or moisture gets to it. If you really want to weatherproof you vehicle check out the June issue of radio control Car Action on page 192. It shows how to seal servos and totally weather proof your RC. You can also look at these sites
http://www.misbehavin-rc.com/links/links-articles.asp and
http://www.hobbytalk.com/modules.php...rder=0&thold=0 .