What's Leaking From My Car?

Is there anything worse than your car leaving a puddle on your driveway? OK, maybe if you leave a puddle on a friend’s driveway instead — but still, a mystery leak is stressful as you try to figure out just how serious the repair is going to be, and whether it’s safe to drive your car.

We put together this quick guide to help you figure out what exactly is dripping from under your car without requiring a degree in chemistry or, you know, having to taste it.

Pro tip: if you’re having trouble identifying the color of the leaking fluid because of the darkness of your driveway’s asphalt, concrete, or gravel, it’s helpful to put a piece of cardboard under the leak to absorb the fluid and better see its hue.

While motor oil looks clear or even golden when you first pour it into your vehicle’s crankcase, over time, heat and stress can turn it light brown, dark brown, or even black. Sometimes an oil leak manifests as a black or brown stain because it picks up dirt and other gunk on its way down from wherever it spouted from on your motor, but occasionally, it will look lighter, especially if it’s fresh.

Once upon a time, engine coolant was almost exclusively green, but as the industry moved away from inorganic acid technology and adopted organic acids and hybrid organic acids, antifreeze’s palette began to expand. Nowadays, you’ll find green, blue, orange, and yellow as the most common coolant colors, with red and pink found more rarely in specific vehicles.

Not sure if it’s coolant just by looking at the color of the puddle? Here are two tips. First, with the engine completely cool, open the cap on your radiator and see what color antifreeze you have in your vehicle. If it matches the leak, you have your confirmation. Some coolants also smell strongly of ethylene or propylene glycol, which has a sweet odor. Touch the puddle with your finger (don’t worry, it won’t hurt you), and then waft it in front of your nose to see if you can detect a similar smell (it might also feel a little bit sticky).

ALSO SEE: What Does the Smoke from My Exhaust Mean?

Remember when we mentioned pink as potentially being engine coolant? More often than not, a pink puddle actually indicates a loss of transmission fluid or power steering fluid, both of which are on the bright red to pink spectrum. As with engine oil, time and heat can darken or dirty the color of either of these fluids.

Brake fluid leaks are dangerous because the system relies on hydraulic pressure to maintain a safe level of braking power in the system. A clear or yellowish color puddle near any of your wheels, along the sides of the car where the brake lines run, or under the firewall where the master cylinder lives is a serious problem that should have you calling a tow truck, rather than trying to drive there on your own. As this fluid ages, it, too, can darken, so keep that in mind when evaluating where underneath your vehicle you found the stain.