If something has metal parts and moves, then fluid is most likely lubricating it. There are lots of moving parts in a car and many kinds of fluids. Fortunately, fluids differ in color, texture, and smell. Once you know what to look for, finding the source of your leak is much easier.
General Fluid Leak Tips
- A puddle that is 3 inches or wider under your car is considered a serious leak and requires immediate attention.
- A puddle between 1 and 2 inches wide is referred to as "seepage" or a "drip." Unless it’s brake fluid, the condition isn’t as serious.
- The morning after your vehicle is serviced, check underneath the car for fresh fluid. If any exists, immediately call the repair facility.
Common Fluids Found Beneath Your Car
Water from the AC or defroster system is one of the most common fluids you may find. Water is formed when moisture in the air comes into contact with the system and condenses. It usually drips under the center right or center left of the vehicle. This is a normal byproduct, and seeing this under your car is no cause for alarm.
Commonly light to dark brown or black in color, engine oil feels slippery and may have a dirty, burnt-rubber smell. To check the engine oil level in your car, see your owner’s manual to locate the engine oil dipstick. If the oil level is low, but still registers on the dipstick, top off the oil at your earliest opportunity. Be sure to mention the leak at your next scheduled service. If the oil level does not register on the dipstick—before you drive the vehicle—add enough engine oil to reach the full level on the dipstick.
Note: Do not overfill. Too much oil can cause more harm than too little oil. Contact your service center as soon as possible.
Engine coolant is usually watery and slippery to the touch. It may be light green, yellow, pink, blue, or even purple. It usually drips near the front of the engine or beneath the radiator. After the engine has cooled down (we hope you’re reading this first!), check the fluid levels in the radiator and coolant reservoir tank. If either is low, top them off with distilled water. Do not use tap water—it contains minerals that can lead to cooling system corrosion. The number one cause of serious engine damage is loss of coolant. If your car consistently loses fluid, contact your repair facility immediately.
Less Common Fluids Found Beneath Your Car
Automatic Transmission/Power Steering Fluid
These fluids can be similar and sometimes identical, so have a professional repair facility confirm the leak. Automatic transmission/power steering fluids are usually reddish to reddish brown in color and feel oily. Leaks are usually found under the transmission or transaxle. These fluids also may leak from a transaxle cooling line near the radiator.
Power steering fluid leaks are found under the front of the engine near the power steering pump or toward the rear of the engine at the steering rack. Check the fluid level. If it doesn’t register on the dipstick, immediately contact your repair facility. If fluid is still on the dipstick, top off the fluid, and monitor how much and how quickly it’s leaking. If there is regular loss, have your vehicle inspected by a professional.
Manual Transmission/Differential Fluid
Leaks of this thick oil, which has an objectionable, rotten-egg smell, are found under the front and rear differential, manual transmission, or transaxle. It’s difficult to check these fluid levels, so have your vehicle inspected by a professional.
Fortunately, leaks of this fluid aren’t common. Brake fluid looks like white wine when it's new and dark tea when it’s old and dirty. Because brake fluid is based on vegetable oil, it feels oily. If you find leaking brake fluid, check the level in the brake master cylinder reservoir. If the level is low, top it off. Brake fluid eats through paint with zeal, so use caution when topping off. Use only the DOT-grade brake fluid recommended in your owner’s manual. If leaking continues and the fluid level is below the midpoint, have your car towed and inspected for a brake fluid leak. This is a real safety issue.
If your car has a manual transmission, it may use a hydraulic clutch, which also uses brake fluid. However, for safety reasons, the clutch and brake reservoirs are almost always separate, even if they use the same filling point. If there is a brake fluid leak and the brake master cylinder is full, then it is most likely a clutch fluid leak. One indicator is that the clutch won’t operate as easily; sometimes it can be impossible to shift gears.
Daniel Dillon has twenty-two years of experience as a licensed Smog Technician in California. He helped write test questions for the California Smog Technician Exam and has performed Consumer Assistance Program and gold shield diagnostic work for the state. He was also an instructor for SnapOn Tool Corporation.