What Is the Fluid Leaking From My Car?

There is something dripping from your car. If it's water, don't worry. If it's something else, here's how to figure out what it is.

Fluid leaks from your car are not uncommon, and most should be checked out as soon as possible — especially if the liquid is gasoline or brake fluid. Determining the cause of the problem starts with identifying the dripping fluid.

If it truly is water, there are normal reasons a water trail shows up under a car after it’s parked. The water condensation from the air conditioning system drips near the back of the engine compartment during normal operation. It is also customary to see water pooling near a vehicle’s tailpipe from normal exhaust condensation, and that is nothing to worry about.

If it’s not water, you’ll have to figure out which of the other seven car fluids it is. Then you’ll know whether it’s a DIY fix, or if it’s time to bring your vehicle in for service.

Identifying the Cause

The main considerations when it comes to fluid leaks are color, feel and location (front/back, left or right side).

Always check fluid levels first, then top them all off. Be extra careful not to spill any fluids on or around the engine compartment. To verify which fluid is leaking, once the engine has completely cooled, place a piece of white paper or cardboard under your vehicle in the area where you’ve noticed the leak.

Fluid Color Coding and Texture

Coolant or anti-freeze: Bright green or orange, pink, blue, or yellow. Slimy with a sweet smell. Look at the radiator hoses, coolant reservoir and radiator. If the leaking fluid at the tailpipe has a sweet smell, it indicates coolant from a bad head gasket or other failed internal engine part is burning in the combustion chamber.

Engine oil: Yellowish (new oil) to light brown to black and slick to the touch. Common causes are the oil pan drain plug, oil filter or gasket, or oil spilled on the frame while replacing the oil filter.

Gasoline: Clear and thin, with the distinct pungent odor of gasoline. Check the fuel hoses and lines, fuel filter connections and gas tank. Never drive a vehicle that has any type of fuel leak.

Brake fluid: Although rare, will be clear (when new) to yellow to light brown with a slick oily feel and a strong bitter/sour odor. Like a gasoline leak, never drive a car if you suspect a leak in the brake fluid hydraulic system.

Transmission fluid: Light red/pinkish (when new) to dark brown. Will feel oily but thinner than engine oil, and usually has a heavy petroleum odor. Leaking transmission fluid is most likely due to a pan gasket, cooler lines or external seal.

Power steering fluid: Reddish or light brown (when new) to dark brown/black. It feels like motor oil, but thinner. Usually the power steering high-pressure line or fluid reservoir.

Windshield wiper fluid: Blue, green or orange with the consistency of water. Check the reservoir for cracks and the fluid lines/hoses for leaks.

Water: Clear, odorless and it will feel like water! In addition to air conditioning and exhaust system condensation, sunroof drains allow melting snow and rain water to exit (depending on the vehicle) by the back door or rear bumper.

Stop-Leak Additives

There are several highly-regarded aftermarket sealant additives that, if used correctly, can be added to the oil, transmission fluid and radiator to temporarily help stop minor leaks. (Forget the, “If one is good two is better principle” here.) The additives help swell O-rings and gaskets that shrink and harden due to age, heat and pressure, or seal up a tiny hole in the radiator. Car additives are not for every application. You wouldn’t want to use a radiator stop-leak additive to plug a leak in the coolant reservoir, for example.

Even a small leak can be an indication of a bigger problem. With this information in hand, you will have a better idea if the leak is a DIY fix, or if you’ll need to bring your vehicle to your mechanic. Remember that any fluid leaking from car can be a minor fix or require a more complicated repair.

Robert Lacivita
Bob Lacivita is an award-winning auto technician and career and technical educator and freelance writer who has written about DYI car repairs and vehicle maintenance topics, as well as writing state, federal and organizational foundation grants, and helped design a unique curriculum delivery model that integrates rigorous, relevant academic standards seamlessly into technical/vocational training, for more than 20 years. His work has been featured in Family Handyman, a Reader's Digest book and Classic Bike Rider magazine, among others. Bob and his wife lived through 20 years' worth of DIY home remodeling while parenting two (now grown) boys and now relax by watching their three fabulous granddaughters.