What's Leaking Under My Car?

That little spot underneath your car may be trying to tell you something. Old Porsches leak, but your late model Honda should be tight as a tick. If you've got a recurring drip, puddle or spot in your parking area, now would be a good time to figure out what's leaking. Unfortunately, looking under the hood or at the underside of your car or truck doesn't always reveal an answer. Thanks to road grime, even a healthy engine is home to all kinds of goop. 

To solve the puzzle, we'll help you identify your leaky fluid by its properties like color, texture, and smell.

Automatic Transmission Fluid: Dextron Type

Automatic Transmission Leak: Dextron type.

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Dextron type automatic transmission fluid is a deep red and has a sharp odor. It is fairly thick and will tend to sit on top of a driveway and soak in slowly.

Power Steering Fluid

This is a power steering fluid leak spot and a sample of the fluid.

Matt Wright/ThoughtCo

Power steering fluid is a slightly yellowish liquid of medium thickness, kind of like cheap waffle syrup mixed with water. It soaks into concrete quickly. It has very little smell but a keen nose will detect a dull, mechanical scent. It is a hydraulic fluid.

Power steering works by creating what is known hydraulically as a pump-and-dump system that uses hydraulic fluid, pressurized by your power steering pump to help the steering rack push and pull the wheels from one side to another when you want it to. When the fluid gets low, there isn't enough volume in the system to keep steady pressure in the direction you want it, which causes the steering to feel like it's slipping. Other times it will make the power steering pump squeal as it is starved for fluid.

Windshield Washer Fluid

This blue liquid indicates a windshield washer fluid leak.

Matt Wright/ThoughtCo

Windshield washer fluid is very thin and has a slightly sweet smell that's like a mix of coolant and window cleaner. It can be blue, green or orange, but otherwise will have similar properties. It soaks into concrete quickly.

Don't refill your windshield washer with plain water if you live any place that can see freezing temperatures. Even doing so in the summer can be catastrophic if you forget to switch the fluid for real stuff before winter. A frozen windshield washer system can crack your fluid reservoir, ruin the electric pump, crack all of your washer hoses under the hood, and even crack your plastic windshield sprayers. This can add up to be a very expensive repair. Don't forget you may have a washer for the rear window, too!

Brake Fluid

Brake fluid leaks should be dealt with immediately.

Matt Wright/ThoughtCo

Brake fluid leaks are nothing to play with. If you suspect you have a brake fluid leak you should diagnose it with certainty, even if you need to take it to a repair shop. Safety first!

Brake fluid is similar to power steering fluid in all aspects. They are both hydraulic fluid, so their properties are similar if not identical. Brake fluid is of medium thickness and has a dull, mechanical smell. It is slightly yellow in color.


If you have a radiator or other coolant leak, repair it soon or you'll be stranded.

Matt Wright/ThoughtCo

Coolant (antifreeze) leaks are probably the second most common, with oil taking the top spot. Coolant leaks will slowly deplete your engine of precious coolant leaving it susceptible to overheating. But that's not the only negative to a coolant leak—coolant can be deadly to animals. Even a small amount of coolant ingested by an animal can kill it, so proper cleanup of coolant leaks is as important as addressing the leak itself.

Coolant can be pinkish or greenish, but most of the time you'll find the green variety. It has a sweet smell and is somewhat viscous.

Did you know that as coolant breaks down, it can begin to react with the metals inside your cooling system, eventually breaking it down and causing a major leak? A number of vehicles that used aluminum heater cores are very prone to this type of mess, which results sometimes in hot coolant being sprayed all over the driver's feet! It's a good idea to flush your radiator annually to avoid any chance of this.

The Classic: Oil

Engine oil leaks are the most common.

Matt Wright/ThoughtCo

Without a doubt, oil is the most likely fluid you'll find underneath your engine. Used engine oil is dark brown and smells slightly gassy. I say slightly because if it smells very gassy you may have other problems that need to be looked into. It soaks into concrete slowly and leaves a dark residue behind. You might also smell an oil leak before it is serious enough to leak onto the driveway. Hot oil smells like something cooking, but not something you're interested in eating. If you smell a hot oily smell, open the hood and check for slight hints of smoke coming up. Cars with high mileage often have minor oil leaks and can go years without any real problems. If you find an oil leak, it's a good idea to have it checked out by somebody who knows what they're looking at.

Always check your oil, and change your oil regularly!