Look for Obvious Leaks
One clear indicator of a problem under the hood (or really anywhere on your vehicle) is the presence of fluid beneath your parked truck. But how do you determine if you're seeing coolant and not some other type of fluid? Typically, it's fairly easy to determine the specific type of fluid your truck is losing based on the fluid color and location of the puddle. In years past, all vehicles used engine coolant that was the same bright green color, and it had a very sticky-sweet smell. Now, coolant comes in a variety of colors ranging from the familiar bright green to red, orange and even pink. Different manufacturers have different standards when it comes to the fluids they fill their vehicles with.
At this point, the color of your truck's coolant doesn't matter quite as much as the fact that you've got a leak somewhere in your cooling system. The various fluids that circulate throughout your vehicle's many different sealed systems -- such as your cooling system, engine, transmission, brake system, transfer case and so on -- are meant to stay trapped inside until they're intentionally drained and replaced. Fluids lubricate and cool moving parts within your vehicle, and your truck's cooling system is no exception. To put it in the simplest terms: If you see a puddle of coolant beneath your truck, you have a leak. And if you have a leak, that means you're in danger of running low on (or running out of) engine coolant, which would definitely cause your engine to run hot or even overheat. So, don't delay in getting that leak repaired, or you could end up with a hefty repair bill.