How to identify 11 car fluid leaks

Posted in Car Care on June 26, 2018

A lot of different fluids can leak out of your car, To help you identify them, place a plastic container where the leak occurs, or if the leak is very small, a piece of white paper to capture its color.

Leaks are identified by physical evidence — smell, color, texture, etc. Once the leaks source is identified, sometimes simply tightening a clamp or bolt may solve the problem.


Usually green or yellow liquid with a faint, sweet odor. Old coolant will be rusty or dirty brown.

Look for leaks at the radiator, upper and lower coolant hoses, heater hoses, engine core plugs. Poisonous.

Automatic transmission fluid

Usually a light red oil. Compare it to that on the transmission dipstick.

The source is the automatic transmission, power steering pump, power steering hoses.

Battery acid

If it has a sulfur-like smell, it's probably sulfuric acid and water from a leaking battery.

Highly corrosive — if it touches skin or clothing, flush immediately with water.

Brake fluid

Clear, thin, almost water-like.

Leaking brake fluid is a danger sign requiring immediate attention. Get a mechanic to check.


Obvious by its sharp odor. Extremely poisonous.

Check at the fuel tank and all fuel lines.

Gear oil

A heavyweight oil, usually dark or black (a light tan when fresh).

Used in manual transmissions. axles, differentials; may show up on the CV axle boots of front-wheel drive vehicles.


Very thick, sticky. Compare it to residue near grease nipples.

Minor leakage after a grease job is normal.

Power steering fluid

Automatic transmission fluid (ATF) is commonly used and is often red.

Compare to fluid in power steering pump reservoir.

Shock absorber fluid

It usually shows up as a dark stain on the shock body itself.

Check all shocks. If leakage is found, replace the shock.


If it looks and smells like clear water, it’s condensation from the air conditioner. This is normal.

Windshield washer solvent

Bluish in color, smelling of detergent or alcohol.

Persistent leakage indicates a cracked fluid reservoir or leaking hoses between the reservoir and the windshield. Poisonous.