How to Diagnose Car Leaks by Location, Color, Smell, and Consistency (Updated 2020)

It's hard to understand car leaks at first. But the good news is that they leave trails that allow you to recognize what's really going on.

Understanding Your Car’s Leaks

There are four things to consider when diagnosing what’s dripping from your car: location, color, smell, and consistency.

Step One Know the exact location of the leak

You can learn the exact source of the leak by placing pieces of white cardboard, bond paper, or aluminum foil under the front, middle, or back part of your car. This is important, since it will give you an idea where the fluid is dripping from and what color and consistency it has.

Don’t use your car for a day, and make sure to park it on level ground. Let the cardboard, foil, or pieces of paper stay there overnight. 

The next day, check for spots, and note the exact location. This will give you an idea where the leak is coming from.

Step Two Determine the fluid’s color, consistency, and smell

Once you know the location, then check out the table below to diagnose the possible problem:

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ENGINE OIL / MOTOR OIL

Light Brown to Black

(Semi-Thick to Thick and Slippery)

Smells like: Cooking oil

It’s not really that serious if you find a little engine oil drip, but if you can smell burning oil while driving, or the drips on the ground smell gassy with a "cooking oil" smell, then it might be an engine oil leak.

This becomes all the more true if you check the engine oil dipstick and the oil is under the low level mark. The level should be in between the top and low levels, and if it isn’t, then something’s wrong.

Don’t drive when your car has a low engine oil level, or there’s a huge puddle of oil slowly seeping out from your car's engine. If you do, then you risk damaging your vehicle. Have a mechanic inspect your engine right away.

FUEL 

Light Gold / Amber (Gas); Light Gold / Amber with Bluish Tint (Diesel)

(Thin and Watery)

Smells like: Gasoline

Both gas and diesel look clear when they drip on the ground, although with diesel, there’s a slight bluish tint that you see when viewed in some angles. Fuel leaks are easy to spot because of their smell. You should be familiar with it whenever you gas up your car.

Remember: Just because the fuel tank is at the rear side doesn’t mean it will just leak near that location. A car’s fuel tank can run from the fuel tank to your car’s engine, so don’t be surprised if you see leaks everywhere.

TRANSMISSION FLUID

Reddish / Pinkish / Brown

(Thin or Thick)

Smells like: Petroleum

Often, these leaks are the result of a worn-out seal or a hole somewhere in the return line. One early indicator of an automatic transmission leak is when your car is revving up but it’s not going into any gear. There's also a petroleum with a hint of fishy odor when you smell it.

Note that the leaks may not always be at the front. In some cases, they can also be at the middle part of your car. Automatic transmissions use transmission fluid, while manual vehicles use gear oil. Check you car’s manual to see the proper way of checking for this fluid, since manufacturers have their own way of doing this.

POWER STEERING FLUID

Reddish or Light Brown

(Thin and Oily)

Smells like: Burnt Marshmallow

It almost looks like a transmission fluid, but unlike a power steering fluid, the transmission fluid can also be seen in the middle portion of your vehicle.

Some power steering fluid almost look yellowish-brownish, and has a medium thickness. But the typical ones are thin in consistency. Whatever the case, the first thing you need to do is check the power steering reservoir. The level should be in between the high and low markings. If not, then there could be a problem.

Other signs to look out for: you hear a whining noise when you’re turning the steering wheel, especially when you're driving on tight corners or low acceleration. There's also a burnt marshmallow with a hint of fish-oil smell to it.

BRAKE FLUID

Clear to Brown

(Slick / Slippery / Medium thickness)

Smells like: Fish oil

This is one of the most dangerous leaks that you shouldn’t take for granted. Usually slippery than an engine oil or transmission fluid, brake fluids can increase the force of your foot when you press down on the brake pedal, and even losing a small amount while you’re driving can affect how well your brakes will work. So this is something that needs to be repaired right away.

Brake fluids often smell like fish oil.

COOLANT

Yellow, Pink or Green [Depends on the manufacturer>

(Slimy and Greasy)

Smells like: Sweet, like Maple Syrup

The coolant is easy to identify, since it's often brightly-colored yellow or green. And they smell sweet, like candy or maple syrup. A little coolant drip can be harmless for old cars, since they will only indicate that you need to add a bit more to the reservoir. However, if your car is a new model and is leaking a lot, then it's a bad sign.

Oftentimes, coolant leaks can be found behind the grill of a vehicle — where your radiator is located. Still, there’s a possibility that you’ll find them leaking some place else, since some coolant hoses are in the passenger compartment as well.

Best thing to do first is to check the coolant overflow tank, and see if the level is below the low-level marking. You can also let your engine cool first, and peer inside your radiator. If there isn’t any brightly-colored liquid there, then your coolant is probably low.

Remember: Don’t drive low on coolant. You don’t want your engine to overheat while you’re in the middle of a highway.

WATER

Clear

(Thin and Watery)

Smells like: Odorless

When you find water leaks on your car, then suspect it’s your air conditioner. This is especially true if the weather is humid, hazy, and hot.

Air conditioners work by removing the moisture from the air in the passenger compartment, and often this moisture becomes water that gets drained down through a rubber hose under your car. Aircon hoses are located differently, so don't be surprised to find leaks everywhere in your car.

So don’t panic when you see a huge pool of water on the concrete. This might just mean that the weather is extremely humid, and the air conditioner is working double time to drain the moisture it’s taking inside the vehicle.

WINDSHIELD WIPER

Blue / Green / Pink/ Purple / Orange [Depends on the manufacturer>

(Thin and Watery)

Smells like: Glass Cleaner

Just like your coolant, it's easy to spot a windshield wiper -- just look for a brightly colored blue, purple or green fluid. Check your windshield wiper fluid reservoir together with the tubes that carry it for signs of holes in case you find leaks. Then go to a mechanic and have them repaired.

This type of leak isn't that serious. Still, they can cause a lot of inconvenience if your windshield wiper isn't working.

Final Word

Don't procrastinate when you find a leak -- have them repaired immediately. Not only will this help you save money, but it will also guarantee you and your family's safety when driving on the road.

Updated on September 18, 2020 by Gail Alcabaza

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