Are your Jetta's windows fogging up from the inside? Does it seem abnormally humid in your Passat? Do the floor mats seem wet even on dry days? If any of these symptoms sound familiar to you, you have a leaking Volkswagen heater core. Working much like a small engine radiator, the Volkswagen heater core provides heat to the passenger compartment on cold days by circulating warm engine coolant through its tubes. That's a good thing on one hand, since the Volkswagen heater core allows you to warm up the interior without using any extra engine power or gasoline. You're simply using the Volkswagen heater core to extract heat that was going to be radiated to the outside air anyway. On the downside, the construction of the Volkswagen heater core means that it's going to go bad someday, since copper and aluminum don't last forever. To make matters worse, the Volkswagen heater core is located inside your car. That means you have a potential source of hot water sitting just inches from your legs. Before you slap a 'for sale' sign on your VW, though, take comfort in the fact that a Volkswagen heater core rarely experiences a catastrophic failure. Instead, the Volkswagen heater core usually takes a long road downhill, starting with pinhole leaks, cracks in the tubing, and other minor maladies. Of course, you'll have to replace the Volkswagen heater core if you don't want your floorpans to rust out, but the chances of being scalded are extremely slim. Just in case, though, don't ignore the signs of a bad Volkswagen heater core. Get your Volkswagen heater core buttoned back up at the first indication of an interior coolant leak.