The inside of your Hummer contains quite a few cubic feet of air, requiring an effective Hummer heater core if you're going to get enough warmth in the wintertime to keep you comfortable. Don't worry, though: The H1, H2, and H3 all come with an oversized Hummer heater core capable of recreating the Sahara in your passenger compartment regardless of what it's doing outside. But what happens to that Hummer heater core five, ten, or fifteen years down the road? The answer depends upon how well your truck has been cared for. If regular coolant flushes have been part of its maintenance regimen, chances are the Hummer heater core will be trouble free for the life of the vehicle. If, on the other hand, regular maintenance is something that's always been left for 'the next owner,' you may find a vehicle with a Hummer heater core that's leaking all over the passenger compartment. And the problem with a leaking Hummer heater core is multifaceted: To begin with, the antifreeze that leaks out of the Hummer heater core and onto your carpet is both poisonous and sweet tasting-something to consider if you have children or pets. Second, that green ooze is half water, so when your Hummer heater core drips it all over the floors it leaks down to the metal that makes up your truck body and begins the rusting process. Finally, while antifreeze is poisonous to us, fungi and mold seem to like it, turning your Hummer heater core leak into a veritable sprinkler for a garden of black mold in your truck's carpet. If those three reasons to repair your Hummer heater core aren't enough, we surrender (and we hope we don't end up buying your vehicle). For the rest of you, get a new Hummer heater core here and get that problem fixed before it gets any worse.