Inside Your Car 7 July 2021

Do you have a Coolant Leak?

Waking up to find a large pool of lime-green liquid covering your garage floor isn’t something you see everyday. Rest assured, it's not related to alien activity or random slime attacks. It is, on the other hand, a sign that your car has an engine coolant leak. It may not seem like a big deal on the surface, but a coolant leak isn’t something you want to hang around.

What exactly is engine coolant?

Car engine coolant plays an important part in a car's cooling system. It regulates an engine's overall temperature, preventing it from freezing or overheating. You will find engine coolant, which is a combination of half antifreeze and half water, in the engine radiator. A pump then circulates the engine coolant through the radiator, engine and heater to keep the car running at an appropriate temperature, regardless of how cold or hot it is outside. If your engine is low on coolant - due to a leak perhaps - this can cause the engine to run too hot and overheat which can sustain some very expensive and potentially terminal damage.

Signs of an engine coolant leak

  • A lime-green liquid puddle under the car. This puddle could also be orange, pink or blue-green as different coloured dyes are used to differentiate the antifreeze from other liquids in the engine.
  • A sweet aroma around the outside of the car after driving it. This is the scent of antifreeze, which is in the coolant.
  • Your car is running extremely hot or overheating.

Locating the coolant leak

If you’ve experienced any of the above signs, there is likely a leak somewhere in the engine, which calls for some investigation:

1. Start by driving the car until it has warmed up and park it somewhere where the surface below is dry and clean.

2. Shut off the engine and let it cool down completely before moving on to the next steps. About 15 minutes should do it.

3. Come back to the car and check if a puddle has formed under or near the front of the car. If there is a puddle, lift the hood and inspect the engine bay for any signs of leakage.

4. Check for a light coloured residue around the radiator cap, hoses throughout the engine or on the radiator itself. If you can’t locate a leak at any of these points, scan the entire engine compartment. You can also sniff around the engine for the sweet antifreeze scent to locate where the leak may be coming from.

5. If there is no puddle, but you smell a sweet aroma, scan the underside of the car to see if any parts have collected droplets or seem to be catching stray liquid.

6. If the sweet smell seems to be stronger inside your car as opposed to outside, this could indicate the coolant leak is inside the heater which can be hard to locate without pulling the car apart.

When you’re losing coolant but no leak can be located?

If you still can’t locate the source of the radiator coolant leak, check your car’s coolant-recovery tank. You’ll find the indicator on the side of the translucent plastic tank. Inspect the coolant level; it should be between the “min” and “max” markings. If it is, then the leak is probably unrelated to the coolant. However if it is below the minimum, this means the leak is related to the coolant and a repair is needed.

How to complete a coolant leak repair

If the leak looks like it was coming from near a hose clamp, a simple fix using a screwdriver to tighten the clamp could be all that is needed. However in most other situations, a DIY coolant leak repair is easy to get wrong - consulting with a technician is your best bet. So, if you’ve discovered or suspect an engine coolant leak, bring your car in to your nearest mycar for a coolant leak repair.

How to drain coolant from the engine block

Fortunately, there are ways to prevent an engine coolant leak from occurring. This requires a regular maintenance schedule which involves changing the coolant in your radiator. Old coolant that sits in your radiator for too long, can become acidic and eat away at the aluminium casket - inevitably resulting in a leak. Therefore regularly draining and replacing the coolant from the engine block can save you future hassles. To do this:

  • Remove the lower radiator hose and collect the old coolant in a bucket.
  • Next, remove the top radiator hose and flush the system out with a normal hose. Continue with this until the water runs clear out of the bottom of the engine.
  • Replace the coolant with a fresh batch and reattach the radiator hoses.

The exact process can differ from car to car, so be sure to refer to the vehicle manual before performing a cooling system flush. In saying this, the procedure itself can be quite complex so unless you have experience with car engines, best leave it to a mycar professional.

Tips for safe engine coolant disposal

Engine coolant is composed of toxic properties that can be harmful to humans, animals and the environment, therefore it needs to be properly disposed of after being drained. Do not flush it down a drain or dispose of it in the garden. For proper engine coolant disposal, transfer the coolant to a large plastic container and take it down to your nearest hazardous waste or recycling facility. Often auto part stores are also happy to take old engine coolant for recycling.

How to manage an engine overheating

In some situations, your radiator coolant leak may have gone unnoticed or unresolved, causing the engine to overheat - so what do you do when this happens? Signs of a car engine overheating can include steam coming from under the hood or the engine temperature gauge spiking to high. When this happens you need to cool down the car immediately to avoid serious damage. You can do this by either:

  • Cranking your car heater to full. This may seem counterintuitive but it actually takes the pressure off the engine and transfers the heat to the car cabin, cooling the engine down.


  • Pulling over, shutting the engine and allowing the car to cool down for about 15 minutes.


Once the car is cooled, call mycar roadside assistance or carefully restart the car and drive down to your nearest mycar shop where we’ll take a look at the issue.

Other engine overheating causes to be aware of

If your car is overheating, it could be due to many of the causes listed below. In any case, be sure to bring your car in for a check up so the issue can be addressed promptly and safely.

  • Not enough or no coolant
  • Broken water pump
  • Radiator issues
  • Low oil
  • Thermostat failure
  • Worned out belts or ruptured hoses
  • Blocked heater core

From overheating engines to coolant leaks, mycar has you covered. Visit your nearest mycar location today or contact us on 13 13 28 to book in for a car repair.

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