How to tell if your vehicle has an antifreeze leak

How to tell if your vehicle has an antifreeze leak

If you notice a strange sweet smell when your car stalls, then your car may have an antifreeze leak. Antifreeze plays a key role in keeping your engine running properly, so it’s important to know if you have an antifreeze leak.

If your car has an antifreeze leak, it needs to be repaired promptly before it causes a bigger, more expensive problem.

Despite its name, antifreeze does more than just keep your vehicle’s radiator from freezing in the winter. Antifreeze is part of the vehicle’s cooling system that controls the temperature of the engine so that it runs properly and doesn’t overheat.

The engine’s radiator is actually filled with what’s called coolant, a 50/50 mix of antifreeze and water. A pump on the engine circulates the coolant through the radiator, the engine, and the heater so that the engine runs at the proper temperature and doesn’t overheat, no matter what the outside temperature is. If there is not enough engine coolant, it can cause the engine to get too hot, which can affect performance and fuel economy. Even worse, the engine can overheat, causing expensive and possibly even fatal damage.


If your vehicle is losing coolant, you need to determine where the coolant is leaking from, how quickly it is leaking, and then repair or send it in for service. An engine’s cooling system is very complex and has many components. Repairing a coolant leak may be cheap and easy, and can be done entirely on your own by tightening loose clamps on a couple of hoses in the system. It can also be as complicated and expensive as replacing a damaged water pump. Big problems like these require the diagnostic skills of a technician and the various tools of a repair shop to fix.

Clues to an antifreeze leak

A sweet odor that can be smelled outside the car and emanates from inside the car after driving it. The odor can also be smelled from behind the steering wheel.
When parked, puddles of lime green, orange, pink, or blue-green will appear underneath the car. Antifreeze manufacturers use these dye colors to distinguish between coolant and other fluids used in cars. Engine oil is golden or black (when dirty) and transmission fluid is dark red.
The car begins to warm up or overheat.
How to Find a Leak
To find a leak, first drive the car until it is fully warmed up, then park the car on a clean, dry surface and, if possible, in the driveway.
Turn off the engine and let it cool down. NOTE: When the vehicle is fully warmed up, the coolant is at boiling and high pressure. Do not remove the recovery tank cover or radiator cap until the engine has cooled sufficiently. They are located under the hood. The diagram below shows the location of the radiator cap and the translucent plastic recovery tank cover. Most recovery box covers are labeled with symbols similar to those shown. Some cars do not have a radiator cap.

After the car has been parked for 15 minutes, look under the car to see if there is a puddle of fresh antifreeze. If there is no puddle, but you smell the sweet aroma of antifreeze, get down on your hands and knees and scan under the car to see if there is anything wet or covered with water droplets. Note: Condensation often forms and leaks to the ground from the air conditioning system, but what drips out of the air conditioning system is pure, clear water.
If small puddles or coolant stains appear under the car near the front, lift the hood and start looking into the engine compartment. This is also a good time to sniff around to see if you can smell antifreeze.
Look for signs of coolant leaks – light-colored residue or stains – around the radiator cap, on the hoses throughout the engine compartment (check the ends of the hoses where they clamp to other parts), and on the radiator itself. If there appears to be a leak near the hose clamps, try tightening the clamps with a screwdriver. If you don’t see any obvious signs of a leak, scan the entire engine compartment; the leak could be coming from somewhere else under the hood.
If the odor is stronger inside the car than outside, the problem may be inside the heater. The heater utilizes a small radiator-like “core” to heat the air inside the cabin. If the carpets are damp or the windows tend to fog up, the heater core may be leaking. Heater core leaks are difficult to locate and even more difficult to repair because the heater is part of the air conditioning system, which is buried behind the dashboard. If this is the case, call a technician unless you are good with a wrench.
If you can’t find the leak
Just because you can’t find a leak doesn’t mean there isn’t one. Check your vehicle’s coolant level after the engine has completely cooled down to see how much fluid is in the vehicle’s coolant recovery tank. The coolant level indicator is located on the side of the translucent plastic tank. Most tanks have clear minimum and maximum markings. The coolant level should be between the minimum and maximum marks. If the tank is full, the odor you smell is probably not an antifreeze leak. If the level in the tank is below the minimum mark or dry, there may be a problem, at which point you should consult a professional technician. They can use a cooling system pressure tester to find the source of the leak.

Driving a car with an antifreeze leak
How long can I drive with an antifreeze leak? We recommend that you have it repaired as soon as possible. Cooling system problems don’t get better on their own and can get worse quickly. You don’t want to be stranded on the side of the road because you ignored the early signs of an antifreeze leak.

If you’re the type of person who likes to “take your chances” on a minor (slow) coolant leak, and it’s summer, you may be able to drive for a few more days, as long as you fill up your cooling system when the water level is low. However, it’s a good idea to top off the cooling system at a 50/50 ratio of antifreeze to water, especially in the winter. On cold winter nights, the water in your engine can freeze and expand. This expansion can easily lead to a blown radiator, cracked cooling system hoses, or even a cracked engine block or head, which can destroy the engine. Antifreeze prevents any damage from occurring by lowering the freezing point of the coolant to about -35 degrees Fahrenheit. Again, it’s best to have your car inspected as soon as possible to prevent more serious and expensive engine damage.


Finally, different cars require different types of antifreeze. There are three main types of antifreeze: old-fashioned ethylene glycol (green dye); propylene glycol (orange or yellow dye); and the newest mixed organic acid technology (yellow, green, pink, blue, purple or orange). The different types cannot be mixed. Refer to your owner’s manual or consult your dealer for the correct type of replacement.

IMPORTANT: Glycol antifreeze is highly toxic when ingested. Glycol antifreeze has a faint sweet odor and is a serious hazard to children and pets.

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