I bought my 1989 LX 5.0 in September, and since I bought it, it hasn't had an overflow tank. Yeah, I know, not a huge deal, but I got one cheap off of eBay. When I unscrew the cap, I can see this one has an overflow sensor. On the cap, three small metal prongs are there. Something plugs into it. What? If I confused you guys and you need pictures, lemme know and I'll snap away.