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Car Fluid Levels: How to Check and Maintain

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Fluids are the lifeblood of your car. Besides being necessary for many of the mechanical components in your car to serve their tasks, fluids also cool, lubricate, and protect them from premature failure. Though your car has many types of fluid, it’s important to investigate any leaks. They’re often early signals of mechanical problems to come, so pay attention to them to avoid costly repairs.

To see if your car has any leaks, and what the leaks might indicate, just park on a relatively clean section of pavement (or a garage floor) and then check for any fresh drips in the morning. If you want to keep your garage floor’s pristine condition, or if your driveway is gravel and you can’t tell, put some newspaper or a flattened cardboard box under the car. Luckily, they each look, feel, or smell a little bit different, so use the following color-by-color reference:

    • Brown or black is usually engine oil. If it smells slightly like gasoline, then it is certainly engine oil. Look around the engine for a leaky seal, a cracked oil pan, or a loose oil filter or drain plug. Engines will normally use (burn) a very small amount of oil, but they’re never supposed to leak oil. If oil can leak out, you can also assume that moisture and contamination from outside can leak inside the engine, potentially reducing its life. Plus, in more extreme cases, oil pressure will be reduced and parts of the engine might not receive proper lubrication.

    • Red is probably power steering fluid. The power steering system is supposed to be a completely sealed system and never lose fluid. Check the fluid level immediately and top it off with what’s listed in your owner’s manual. Fluid loss usually means a failing power steering pump, but have it checked by a mechanic—it could be something simpler and cheaper the sooner you catch it.

    • Reddish-brown fluid is most likely automatic transmission fluid, if your car is so equipped. If it’s dirty, it will smell faintly like burnt toast or roasted nuts. Manual-transmission gear oil tends to be more on the brown side, and extremely thick. Again, check the fluid level of your transmission immediately (for many automatic transmissions there’s a separate dipstick to check it). If the fluid is low, have your mechanic look at it as soon as possible. Transmission repairs are usually very expensive.

    • Pale green or pale yellow sweet-smelling fluid is likely coolant. Be especially careful with this—it’s extremely toxic and pets are attracted to its sweet smell. Coolant leaks can originate in many different places underhood, but start with the radiator and follow the hoses around until you find the wet spot. If you still can’t find it, let the engine heat up to normal temperature for a few minutes, then shut off the engine and look for escaping steam or droplets of coolant. Be especially careful around the electrically operated fan, because it could come on at any time, even if the engine is off.

    • Blue, odorless liquid is usually just windshield washer solvent. Check the fluid reservoir for leaks, and look for cracks or rough areas along the rubber tubing. If it’s the tubing, you should be able to easily find replacement tubing at an auto parts store and cut it to fit. Be very careful not to let any surrounding dirt and debris get into the system, where it could ruin the pump or clog the spray nozzles.
Though it’s not as likely on newer vehicles, if you have a leaky fuel filter or cracked fuel line, gasoline might be leaking. Gasoline won’t leave much of a stain on your driveway, but you’ll be able to smell it. If gas is leaking, this can be extremely dangerous. Do not drive the vehicle. Have it towed to your mechanic, and instruct the tow operator about the problem.

Many newer cars will have large rubber or plastic protective shields underneath the engine bay, making it difficult to locate leaks. Most of the time, these shields are held on by a series of bolts, and they can be removed quite easily with a wrench. Remove the shield after driving the vehicle in the evening, then reinstall it the next morning.

If you noticed something in the past and still think you’re leaking something, take a look underneath the engine bay with a flashlight, or ask your mechanic if he/she sees any leaks.