DIY

Fluid Leaks 101: Find Out What’s Leaking From Your Car

Reading Time: 8 minutes

Is that pool of fluid under your car engine oil, coolant, or something else altogether? Because vehicles contain so many different fluids, most drivers experience difficulty distinguishing one type of leak from another.

Thankfully, knowing the colors (and sometimes, the textures and odors) of the various fluids can help you determine what kind of leak you’re dealing with.

fluid leaking from car
Cars contain so many different fluids that most drivers experience difficulty distinguishing one type of leak from another.

Fluid Leaking From Your Car: What Does it Mean?

Leaks can starve your vehicle of the various fluids that cool, lubricate, and perform other tasks throughout critical systems. You’ll want to fix any leaks as soon as possible.

But before you rush off to the repair shop, it’s helpful to identify the different types of fluids that you might find leaking from your car. Below, you’ll find a guide to what the assorted fluid colors might mean.

Fluid ColorWhat Type of Fluid It Could Be
GreenCoolant
A/C Refrigerant Dye
Automatic Transmission Fluid (Some CVT Transmissions)
Honey-Colored / Semi-TransparentEngine Oil
Gear Oil
Fuel
Brake Fluid
Power Steering Fluid
RedAutomatic Transmission Fluid
Coolant
ClearWater
PinkAutomatic Transmission Fluid
Coolant
YellowCoolant
OrangeCoolant
BlueWasher Fluid
Coolant
PurpleCoolant
BrownDirty engine oil (usually)
But could be anything from dirty transmission fluid to old power steering fluid

Green Fluid

green fluid leaking from car
Green fluid leaking from your car is usually coolant.

Coolant

Green fluid leaking from your car is usually coolant. These days, coolant (also known as antifreeze) comes in a rainbow of different colors. But older vehicles use inorganic additive technology coolant (IAT) that’s almost always green.

Your car can develop coolant leaks from many different places. Common sources include the following:

  • Radiator
  • Heater and radiator hoses
  • Water pump
  • Thermostat housing
  • Freeze plugs
  • Head gasket/s
  • Heater core

Sometimes, you can easily pinpoint a coolant leak with a quick visual inspection. If that doesn’t work, either you (or your mechanic) can pressurize the system using a special tool. Once the cooling system is under pressure, the coolant should begin to drip (or pour) out of the leak, making it easier to spot.

A/C Refrigerant Dye

Although air conditioning (A/C) refrigerant itself is colorless, it often contains green trace dye that’s added for diagnostic purposes. Unlike coolant, the green dye has a neon hue to it.

Refrigerant leaks can develop from almost anywhere in the A/C system. Common locations include the following:

  • Compressor
  • Condenser
  • Evaporator core (you may see dye leaking out of the drain)
  • Lines and fittings
  • Pressure switch
  • Expansion valve or orifice tube
  • Receiver/drier or accumulator

Usually, the dye will cling to the source of the refrigerant leak, making it easy to pinpoint. You can use an A/C leak detection kit (UV light and goggles) to get a better view if necessary.

To fix the leak, a professional will first need to use a dedicated machine to recover the refrigerant. Otherwise, when the system is opened for repair, any remaining refrigerant will escape into the atmosphere—and allowing that to happen is illegal.

Once the refrigerant is recovered, the leaking component can be replaced. A professional will need to evacuate and recharge the A/C system after the repair is complete.

Automatic Transmission Fluid

Although most cars use automatic transmission fluid (ATF) that’s red in color, some vehicles that have a continuously variable automatic transmission (CVT) use green ATF.

ATF is oily to the touch, whereas coolant feels slippery.

As you might guess, ATF leaks can stem from a variety of locations. Here are some of the most common sources:

  • Transmission pan gasket
  • Output shaft seals or axle seals
  • Cooler lines and fittings
  • Torque converter (front pump) seal

Typically, you can pinpoint an ATF leak with a simple visual inspection, or you can have a professional do the job for you. Once you know where the leak is coming from, you can move forward with replacing the offending component.

Honey-Colored or Semi-Transparent Fluid

engine oil being poured
Engine oil is usually honey-colored or semi-transparent when fresh and clean.

Engine Oil

Several different fluids are honey-colored or semi-transparent when they’re fresh and clean. Engine oil is one of them.

If your car is leaking engine oil, here are some of the most common locations where it could be coming from:

  • Oil pan gasket
  • Valve cover gasket/s
  • Crankshaft seal
  • Camshaft seal/s
  • Oil filter
  • Oil filter adapter housing gasket
  • Drain plug
  • Timing cover gasket or sealant
  • Oil cooler lines

Some oil leaks can be found through a simple visual inspection. In other instances, an oil leak will become a huge mess that’s all over the engine. And when that happens, it’s a good idea to clean the engine off thoroughly. Then, run the vehicle to verify the location of the leak.

Once you know where the leak is coming from, you can replace the necessary components to repair the problem.

Gear Oil

Gear oil, which is used in many differentials, transfer cases, and manual transmissions, starts out honey-colored or semi-transparent. You’ll usually find gear oil leaking from one or more of the following locations:

  • Differential cover gasket
  • Output shaft seals
  • Axle seals
  • Case half gasket

Usually, you can spot a gear oil leak by safely raising the vehicle, then taking a peek underneath. Fixing the problem involves replacing whatever component is no longer sealing properly.

Fuel

Gasoline and diesel fuel are semi-transparent. Fuel is easy to recognize because it has a distinct odor. If you see or smell fuel, it’s likely coming from one of the following locations:

  • Fuel lines
  • Fuel filter
  • Injector or injector o-ring
  • Gas tank
  • Diesel high-pressure fuel pump or transfer pump

Fixing a fuel leak involves first pinpointing the leak, then taking the necessary actions to repair the problem. The fix could be anything from a simple fuel filter swap to replacing the entire gas tank.

Brake Fluid

Fresh brake fluid is honey-colored or semi-transparent. In most cases, a car that’s leaking brake fluid will have reduced stopping ability, making it unsafe to drive. You should have the vehicle towed in for repair if you find a leak from the brake hydraulic system.

Here are some of the most common locations for a brake fluid leak:

  • Master cylinder
  • Hydraulic valves
  • Brake lines
  • Calipers
  • Wheel cylinders
  • Clutch master and slave cylinder (manual transmission-equipped vehicles)

It’s usually pretty easy to identify the location of a brake fluid leak. Depending on your skill level, you can choose to either fix the leak yourself or have a professional tackle the job for you.

One thing to keep in mind is that you’ll need to bleed the brake system (unless you’re working on the clutch hydraulics) after the repairs are complete. Failing to do so will result in little to no braking ability when you go to drive the vehicle.

Power Steering Fluid

Power steering fluid can also be honey-colored or semi-transparent, though some vehicles use red automatic transmission fluid instead of dedicated power steering fluid (more about that below).

A power steering leak usually stems from one or more of the following locations:

  • Power steering pump
  • Steering gear
  • Lines

Typically, all you need is a flashlight and good eyesight to spot the source of a power steering leak. You can then either fix the problem yourself (if you have the know-how) or have a professional do the job.

The power steering system will need to be bled of air after the repairs are complete.

Red Fluid

red ATF fluid being poured into car
Automatic transmissions use red-colored ATF.

Automatic Transmission Fluid

Automatic transmissions (and many transfer cases) use red-colored ATF. In some instances, a car’s power steering system may also rely on ATF.

Coolant

Most automakers have begun using organic additive technology (OAT) or hybrid organic additive technology (HOAT) coolant. Toyota and some other automakers use HOAT coolant that’s red in color.

Clear Fluid

clear fluid leaking from car
Clear fluid dripping from your car is usually just water and it’s totally normal.

Water

Here’s some good news: Clear fluid dripping from your car is usually just water. The water forms due to the condensation that builds up when you’re running the air conditioning (A/C) system. Sometimes condensation can form in the tailpipe, too.

Don’t worry—it’s totally normal.

Pink Fluid

pink ATF fluid in car
Pink fluid leaks can mean that your car is leaking transmission fluid.

Automatic Transmission Fluid

ATF is usually described as being pinkish-red in color. So, if you find pink fluid in the driveway, chances are, your car is leaking transmission fluid. Remember: Some cars also use ATF in their power steering systems.

Coolant

Toyota and a few other automakers use HOAT coolant that’s pinkish-red in color.

Yellow Fluid

yellow fluid in car
Yellow fluid is nearly always coolant.

Coolant

Yellow fluid is nearly always coolant. Ford, Chrysler, and some other vehicle manufacturers use yellow coolant in select models.

Orange Fluid

orange fluid being poured into car
Orange fluid is almost always OAT coolant.

Coolant

Orange fluid is almost always OAT coolant. For decades now, General Motors has been using a type of OAT coolant, called Dexcool, in all of its vehicles. Volkswagen and the now-defunct Saab also use orange OAT coolant in select models.

Blue Fluid

blue washer fluid being poured into car
A blue fluid leak can mean a washer fluid leak.

Washer Fluid

If you find a blue liquid dripping from your car, you might be dealing with a washer fluid leak. Nearly all varieties of washer fluid (except for a few blends) are blue in color. Washer fluid leaks almost always come from one of the following locations:

  • Washer reservoir
  • Lines
  • Nozzles

If you’ve been considering taking up DIY auto repair, fixing a washer leak is a good first project. In most cases, the job is easy to do. Plus, there’s very little risk of damaging other parts of the vehicle during the process.

Coolant

A variety of automakers—including Subaru, Honda, Mazda, etc.—use blue coolant in select models. Some other vehicle manufacturers (e.g., BMW and Volvo) use HOAT coolant with more of a turquoise hue.

Purple Fluid

purple fluid being poured into car
Purple HOAT coolant is found in various vehicles, including certain models from Mercedes-Benz, Audi, VW, Porsche, and others.

Coolant

Nowadays, coolant comes in a myriad of colors—including purple. Purple HOAT coolant is found in various vehicles, including certain models from Mercedes-Benz, Audi, VW, Porsche, and others.

Brown Fluid

brown fluid from car in a pan
Most of the fluids that start out honey-colored or semi-transparent turn brown over time.

Brown fluid that’s leaking from your car could be almost anything. Most of the fluids that start out honey-colored or semi-transparent (i.e., engine oil, gear oil, etc.) turn brown over time. ATF also eventually becomes brown from use, as do most types of coolant.

But in most cases, brown fluid is dirty engine oil. Take a peek under the hood and, if necessary, underneath the vehicle. If the fluid is clinging to (or dripping from) the engine, it’s probably engine oil.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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