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How to Tell if You Car Has a Coolant or Antifreeze Leak

By Jason Collins | November 5, 2021

Winter is a challenging time of the year for vehicles. Freezing temperatures are hazardous for a car's radiator. Cold temperatures can have a seizing-up effect on a vehicle's engine and stop the engine from running and lead to lengthy repairs.

To get around this challenge, car owners turn to antifreeze, which is often confused with coolant.

These two substances are actually different, even though they are often used interchangeably. Unfortunately, both fluids are susceptible to leaking, an entirely new problem for your car often represented by a leaking radiator.

We explore a coolant leak versus an antifreeze leak and the best way to repair them.

Is Antifreeze the Same as Coolant?

The simple answer is no. Despite there being two colors of antifreeze, neither type is the same as coolant. The two colors should never be mixed together and should never be poured into the car's engine system by themselves.

Antifreeze also differs from coolant because it contains corrosion inhibitors that prevent rust in the radiator, water pump, and other cooling system components.

A coolant mixture generally consists of a 50-50 split between antifreeze and water. Sometimes, the coolant mixture can contain as much as 70% antifreeze during extremely cold temperatures. The 50-50 ratio is effective in keeping an engine cool that operates at more than 200 degrees, and it will help prevent freezing in temperatures of 30 degrees below zero and even lower.

The addition of water to antifreeze is the distinguishing factor between engine coolant and antifreeze. When antifreeze is converted into coolant, it can effectively regulate an engine's temperature by preventing freezing and overheating.

Common Causes of a Coolant/Antifreeze Leak

A coolant or antifreeze leak can occur for several reasons. Common causes include:

  • A blown radiator hose or improperly sealed radiator hose.
  • A bad hose clamp or poor hose connection
  • Your water pump has failed.
  • Warped head gasket or a blown head gasket.
  • If a foreign object was kicked up by a vehicle in front of you which penetrated the radiator itself.
  • Corrosion inside the radiator.
  • A leaky radiator cap
  • There may be an issue with the expansion tank.
  • There is a hole in your radiator.

An antifreeze or coolant leak can overheat your engine, warp the cylinder head or head gasket, contaminate your engine oil, and leave you stranded on the side of the road.

Symptoms of an Antifreeze Leak

Common symptoms of an antifreeze leak include the following:

  • You may notice a sweet smell coming from the car after driving it. It is easier to pick up the sweet aroma when standing outside the vehicle; however, you may smell it inside the vehicle if it is strong enough.

  • The easiest way to tell if you have an antifreeze leak is to look for puddles underneath the car after you have parked. The puddle may contain lime-green, orange, pink, or blue-green fluid. Engine oil is gold or black when dirty, while transmission fluid is dark red.

  • Your car runs hot or starts overheating, which your temperature gauge will indicate.

How to Repair an Antifreeze Leak

Depending on the root cause of the antifreeze leak, below are some helpful tips on how to repair the leak:

  • Replace Old or Damaged hose clamps

Below is how to replace old or damaged hose clamps:

  • Let your car cool down for five to 10 minutes.
  • Open the hood and unscrew the radiator cap.
  • Locate the damaged or worn hose clamp.
  • Depending on where the hose clamp is situated, you might need to drain some of the antifreeze. Place a bucket below the rubber hose and drain as much antifreeze fluid as necessary to access the hose and clamp.
  • Unscrew the damaged or old hose clamp. If you cannot unscrew it, then you may need to cut it.
  • Slide the new hose clamp onto the freed hose.
  • Tighten the hose clamp.
  • Fill the radiator with new fluid and tighten the radiator cap.
  • Turn on your car's ignition and allow it to reach operating temperature. Inspect the new clamp for any leaks.
  • Replace the Radiator Hose

Below is how to replace a radiator hose:

  • Follow steps one to three for replacing hose clamps; however, for the third step, you will locate the damaged hose.
  • Depending on where the hose is situated, you might need to drain some of the antifreeze. Place a bucket below the rubber hose and drain as much antifreeze fluid as necessary to access the hose.
  • Unscrew the hose clamps on either side of the radiator hose. Inspect the clamps as well for any signs of damage. You may need to replace the clamps too.
  • Slide the two hose clamps onto the new radiator hose and into their respective spots.
  • Tighten the two hose clamps down as firmly as possible.
  • Fill the radiator with new fluid and tighten the radiator cap.
  • Turn on your car's ignition and allow it to reach operating temperature.
  • Inspect the new radiator hose for any leaks.

Sometimes, you may find that you need to replace the radiator itself with a new radiator. While this is a task that you may accomplish independently, using a professional mechanic may be the better option.

Symptoms of a Coolant Leak

  • Puddles of coolant with a sweet smell: One of the most apparent indicators of a coolant leak is the same as that of an antifreeze leak - look for puddles underneath your car after parking. The color may be green, orange, pink, or blue. A sweet aroma is also a great indicator of a coolant leak.

  • Overheating engine: If your temperature gauge reads high or your temperature warning light appears while driving, then the unusual temperature fluctuation may signify that there isn't enough coolant, and you may have a leak.

  • Low coolant level: Your vehicle has a coolant reservoir that holds extra coolant. If your coolant levels are low, then coolant may be leaking while you drive.

  • Coolant warning light: When the coolant level in your car is low, your coolant level warning light will appear. If there is not enough coolant, your automotive engine may be at risk for severe damage.

  • Rust or corrosion of the radiator: Leaking coolant may cause rusting spots or discoloration on the radiator. Rust stains are a good indicator of a cooling system fault.

  • White smoke: The most common symptom of a blown head gasket is white exhaust smoke. White smoke indicates your car is burning coolant, which is leaking into the cylinders.

How to Repair a Coolant Leak

You can patch up small leaks using store-bought automotive sealants or radiator stop-leak concentrates. These products are specifically designed to plug minor internal leaks inside the car's cooling system.

The repairs below for a coolant leak can be quickly done without the assistance of a mechanic, depending on the source of the problem:

  • Change the bad rubber hoses. Replacing a rubber hose is relatively easy; just ensure you purchase a good quality hose and hose clamps to replace all the bad ones.

  • Replace the radiator cap. The radiator cap keeps the coolant inside the radiator. If the cap is damaged, it cannot control the pressure, and it will cause a coolant leak. Replacing the radiator cap will easily solve this problem.

  • Fix the coolant reservoir leak. If the coolant reservoir leaks due to a puncture or small cracks in the reservoir tank, then with some home DIY, you can repair the issue yourself. All you need is some silicone sealant for the affected areas.

You may need expert help from a mechanic for the below common causes of a coolant leak:

  • Replacement of the coolant reservoir tank.
  • Repairs to the head gasket.
  • Replacement of the water pump.
  • The Cost to Repair a Coolant or Antifreeze Leak
  • The cost of repairing a coolant or antifreeze leak depends on the cause and source of the damage and what solutions exist for the auto repair.

Minor repairs, such as replacing and installing rubber hoses, replacing caps, using sealants, and stop-leak concentrates, shouldn't exceed $100.

Major repairs generally cost upwards of $500. Major repairs include problems with the water pump, head gasket, engine block, and radiator replacement. Recruiting a mechanic may cost you labor fees up to $300.

As the old saying goes, "Prevention is better than cure." Rather stay updated with your vehicle maintenance and regularly check your antifreeze and coolant levels, especially ahead of drastic temperature changes. ### A Car's Coolant System

Now that we have broken down antifreeze versus coolant, it is important to understand their part in a car's cooling system before addressing those pesky radiator leaks.

Your car's radiator is filled with a 50-50 mix of antifreeze and water (coolant). A pump on the engine circulates this fluid through the radiator, engine, and heater and maintains an optimal operating temperature for your engine.

Low coolant levels can cause a car to run hot, negatively impacting your vehicle's performance and fuel economy. An overheating engine will result in extensive engine damage and expensive auto repair bills; worse yet, the engine may completely seize.

What is Antifreeze?

Antifreeze is commonly used as one of the basic ingredients of a coolant mixture and consists of ethylene glycol or propylene glycol. When antifreeze mixes with water, the mixture becomes coolant; the cocktail mix found in cooling systems of all water-cooled vehicles.

Antifreeze, specifically the ethylene glycol, is poured inside a car's radiator and helps lower the freezing point of the liquid circulating inside the car's engine. Basically, antifreeze prevents the liquid from reaching the freezing point during cold temperatures. It also helps raise the boiling point of the liquid so that it doesn't evaporate.

Antifreeze comes in different colors and different chemical formulas. There are two common colors of antifreeze, orange and green, which may be the cause of the confusion between coolant and antifreeze. The orange antifreeze is generally the "extended life" antifreeze and lasts longer than the green one because of a different type of corrosion inhibitor used in the mixture.

Different chemical formulas exist for different vehicles. Among the different types of chemical formulations are organic acid technology, inorganic acid technology, and a hybrid mix of the two. If you are unsure which antifreeze to use in your car, refer to your vehicle's owner's manual for guidance.