How I Can Tell What That Leak in My Driveway Is?

Liquid that's leaked from under a car Dominique Landau/ThinkStock

Whether you spot a puddle under your car or just a few drops, there are several possible culprits, and color alone might not explain what it is. How can you figure it out? To be sure, you’ll need to pinpoint where it’s coming from using your eyes and your nose.

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Amber, dark brown or even black fluid is probably motor oil, but it could also be brake fluid. Reddish fluid is usually from the transmission, though it could also be power-steering fluid. Most antifreeze used to be green; now it comes in several hues.

First, if it smells like gas — and it’s not just a few drops you spilled while filling the tank — treat it as a big deal, because it probably is. It’s unsafe to drive a car that’s leaking gas.

If gas isn’t the culprit, start your investigation by dabbing the fluid with your finger and/or a clean paper towel to get a closer look at the color, as well as to smell it and feel it with your fingers (keep reading for more details on this). Your car’s owner’s manual will show the location of fluid reservoirs under the hood, and that could help you identify the leaking fluid.

If you’re really lucky, that initial investigation will show that it’s colorless and odorless, which would mean it’s just water draining from the vehicle’s air-conditioning system, typically in the front on the passenger side. If it’s watery, it could also be windshield washer fluid.

If it appears to be coming from under the hood, narrow the possible culprits down by placing clean cardboard, such as a flattened box, under the engine and transmission immediately after the car has been driven, then check it later. That should give you a better look at the color and help you find where it came from, either by looking up from underneath the vehicle or down from above the engine. Even if fluid isn’t visibly dripping, leaks will leave tracks, and seepage will leave dark spots around gaskets and seals that you might be able to spot.

Ways to Identify Leaking Fluids

Engine oil can be amber (if it’s fresh), brown or — if it hasn’t been changed for 10,000 miles — black, and it will leave slickness on your fingers that’s hard to wipe off. Oil can leak from gaskets and seals on the front or rear of an engine, from valve covers or from the oil pan underneath, so there are several possible sources of an oil leak.

Transmission fluid is usually reddish and slick, though some come in other colors and can be thicker or thinner than engine oil. If you suspect a transmission fluid leak, consult your owner’s manual to see how to check the fluid level. If you can get a clear look at the transmission, check for leaks around the seals or gaskets.

Power-steering fluid is usually reddish, and on some vehicles it’ll be the same fluid that goes into the transmission. Check the fluid level in the power-steering reservoir and look for leaks in the reservoir and the hoses coming from it.

Engine coolant can be green, yellow, pink or another color, so check your coolant overflow tank to see what’s in your radiator. Is the overflow tank empty? Maybe you’ve found your problem. Coolant usually feels like slimy water and has a sweet smell. Leaks can come from the overflow tank, the radiator, the water pump, coolant hoses and elsewhere. For your own safety, wait until your engine is cold before opening the radiator cap.

Brake fluid can be light brown or even clear when new, but it typically darkens as it ages. It’s also slippery — and vital to stopping your car. That’s a good reason to treat a brake fluid leak as an emergency. Check the brake fluid level in the reservoir (usually near the firewall on the driver’s side) and see if you can see any leaks there. The fluid gets pumped through brake lines to the wheels, so leaks could be much further downstream and out of sight.

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A few drops of fluid on your driveway isn’t reason to panic, especially on an older car. Seepage and minor leaks are par for the course on vehicles with several years and thousands of miles on the clock. That said, any leak should be a wake-up call to keep an eye on things before it becomes a gusher, and to regularly check fluid levels (all of them) to make sure you aren’t running low anywhere.

If you’re losing sleep worrying about a fluid leak, ask your dealership or local repair shop to take a look. Draining fluids can be a drain on your wallet, but the earlier they’re caught, the better.’s Editorial department is your source for automotive news and reviews. In line with’s long-standing ethics policy, editors and reviewers don’t accept gifts or free trips from automakers. The Editorial department is independent of’s advertising, sales and sponsored content departments.

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