What’s Leaking Under My Car?

By Cam Benty 03/01/2021 11:00am

Leaking fluid underneath the car

Learn all about car leaks and those drips from underneath your car.

It’s an annoying predicament. You pull out of your garage only to discover that some leaking fluid has defiled your perfectly clean garage floor. Whether it’s green, red, brown or black, the remnants of drips and leaks could signal the start of major auto repair bills. They’re also unsightly. What to do?

Drips and leaks happen for many reasons. The most common culprit is that a hose or hose fitting that transports fluid from one place to another under your hood has failed.

With the large number of plastic components manufacturers use in today’s vehicles to save weight and cost, it is easy for them to crack with age or from some impact. Today, most fluid reservoirs and radiators use some plastic pieces.

Especially fragile are the radiator’s tanks that bracket the radiator core. If road debris kicks up just right, they can crack these parts. If that happens, the chance of a subsequent drip is high.

How to Find the Car Leak

As we all know, telling your doctor where it hurts can help achieve a quick diagnosis. The same holds true for vehicles. Explaining what you witnessed in drips and leaks to your service tech can help expedite a solution. When you arrive at the shop, they will always perform a safety check and analysis of the vehicle, but your observations can help.

The easiest way to find leaks is to start by checking the fluid levels under your hood. If you find that you are low on coolant, refill the reservoir. The same holds true for your power steering, brake, rear end, and transmission fluids. Never overfill these reservoirs but make sure the fluid is at the top of the range.

Tips for Checking Car Fluids

Note that transmission and engine oil dipsticks and fluid reservoirs have markings for hot and cold fluid levels. Using a grease pencil to mark the fluid level position on the reservoir can help when you go back for a recheck. If after driving the vehicle for about a week, you see a difference in a fluid level (make sure that you check when the vehicle is cold as engine heat will cause fluid levels to change), tell your service tech.

Remember there are many reasons why vehicle fluids fluctuate. An engine with worn piston rings or valve guides burns oil excessively and cause the oil level to drop. If you find yourself adding a quart of oil every 1,000 miles, you need to let your service tech know. If this is the case, those drips on the garage floor is the least of your problems because you may be your way to an engine overhaul.

Finding the Leak, Part II

Concerning those drips and leaks, here’s a trick you might try to help that service tech find the root of your problem. First, clean the floor of your garage or driveway removing any liquids. Driveway stain removers are available at your auto parts store or big box home improvement centers and will do a great job.

Next, note where the drips are coming from relative to your vehicle’s position in the garage. Remove the vehicle from the area and lay some white paper towel in the area where you spotted the drips. You should be generous with the amount of towel you use and make sure that you fully cover the area under the engine and transmission.

Next, hold down the toweling with small stones, bricks or, if the surface is smooth and flat enough, masking tape. If you don’t hold the toweling in place, it will move out of position. Finally, after taking the vehicle around the block to reach operating temperature, place the vehicle over the area covered with toweling and wait to see if drips and leaks develop.

When Do Drips and Leaks Occur?

Most leaks will happen in the first 15 minutes of vehicle cool down, but some take longer. After waiting about two hours, you can roll the vehicle back and check for stains on the white paper towel. The key here is to use white paper toweling so that you can interpret the color of the stain.

What Do the Colors Mean?

Vehicle fluids come in fairly standard colors. Red fluid can be transmission or power steering fluid (with some cars, transmission fluid is used in the power steering system). Your power steering unit is generally more forward in your car, the transmission traditionally more rearward, often behind the engine. With front-wheel drive cars, both the engine and transmission can be side by side rather than inline so sourcing drips and leaks can be more challenging.

Your vehicle contains a rainbow of differently colored liquids. Most often green fluid drips will signal coolant leaks. Toyota, however, uses a red coolant. Black and brown drips are generally oil-related issues. A clear oily liquid is probably brake fluid. If you spot a reduction in brake fluid in the reservoir along with a clear fluid drip, it might be advisable to have your vehicle towed rather than driving for service as brake failure is possible.

Passing the Smell Test

Using paper toweling to catch the drips not only helps to discern the leak’s color, but it also helps capture the smell of the liquid in question. Coolant, engine oil, transmission, power steering fluid and rear end gear oil all have very distinct smells that any trained professional will recognize. Bring the soiled sections of your paper towel to the service tech, and almost without question, they will know what’s leaking from the color and the smell.

Your vehicle is a very complex machine. Finding issues like drips and leaks early on is vital to keeping it running well and reduces the chance of becoming stranded in the future. If you find drips on your garage floor, don’t ignore them. They could be letting you know that a system failure is possible. Make sure you check all vehicle fluid levels often, not just when your dashboard lets you know an oil change is necessary. If your fluid runs out, so may your luck.