You go out to your car in the morning or at the end of the work day, and there are drops of liquid, or worse yet, a big puddle, underneath it. You wonder what’s leaking and how bad is it? You don’t necessarily need to call a mechanic or have the car towed off the bat. With a little knowledge and some testing you can figure out what the fluid is what to do about it.
First you’ll want to capture the leaks. It will be hard to get a good look at them on dark pavement, so put down a piece of butcher paper, newspaper, cardboard or aluminum foil underneath your car to catch the leaks. Park the car somewhere flat and level, and weigh down your drip catcher so it doesn’t get blown away by the wind. Once you’ve caught some of the fluid, it’s time to identify it. To do this, you’ll have to use your senses of sight, touch, and maybe even smell.
Identify where the leak is coming from
The first clue you’re going to use to identify your leak is where it’s coming from. If you have a rear wheel drive vehicle (common for pickup trucks, some sports cars, and most classics), a leak coming from the rear of the car is most likely differential fluid. A leak in the rear could also be coming from the gas tank.