How Much Coolant Loss is Normal?

Though coolant lasts incredibly long and doesn’t need to be topped up as frequently as fuel and engine oil, it can drop down. But what if you notice the coolant level dropping continuously? How much coolant loss is normal?

Though many people believe 0.25% of coolant loss every 4 to 6 months is normal, many car enthusiasts think coolant loss is abnormal. In addition, the coolant level in the tank can drop slowly due to numerous reasons, which require troubleshooting and fixing as soon as possible.

Keep reading to understand the reason for losing coolant continuously and its potential causes, along with simple solutions.

How Much Coolant Loss is Normal?

losing coolant no leak no overheating

Losing coolant isn’t normal for a car. Unless you overfill the reservoirs, losing coolant indicates there might be an issue. In most cases, loss of coolant indicates a leak in the cooling system or a blown head gasket. So the actual question should be, “How much loss of coolant is acceptable?”

It depends on the car and its age. However, a very small quantity of coolant loss due to evaporation is normal and can be replaced during the periodic service. It means if the engine is running well and there is leakage or damage, around 0.25% of coolant loss every 4 to 6 months is acceptable. In other words, losing 2 to 3 ounces of coolant every year is quite normal.

If you’re wondering how much coolant loss is normal in the summer, it’ll be slightly higher than in the winter. Hence, you should clean the radiator every couple of years and replace the coolant to increase the longevity of the engine.

How Long Does Coolant Last in a Car?

Coolant is made of antifreeze and water and contains several properties that enhance performance with the aid of additives. The longevity of coolant varies from maker to maker. While some coolants last for around 30,000 km (3 years), some last for 1,50,000 km (15 years). In general, you should change the coolant once a year and not leave it for more than two years.

The longevity of the coolant also depends on the corrosion inhibitor, CI, used in it. In general, four types of CI are used in coolant, and these aren’t interchangeable. So you must use the car maker’s recommended type.

Below is the list of different types of CI along with recommended vehicle and approximate longevity:

Corrosion inhibitor typeRecommended vehicleApproximate longevity
IAT (inorganic additive technology)Used in 90’s and older vehicles50,000 miles or 3 years
Si-HOAT (silicone hybrid additive technology)Used in European automakers, Chrysler until 2013 and Ford until 2011. 100,000 miles or 5 years
OAT, (organic additive technology)Used by Ford since 2011, GM since 1996, Chrysler since 2013, and some BMW, Daimler, and Fiat model150,000 miles or 5 years
P-HOAT, (phosphate hybrid additive technology)Used by Asian manufacturers100,000 miles or 5 years

It’s vital to change the coolant before it becomes polluted. Older coolants can cause acid buildup and contamination from scaling or rust. This can reduce its resistance to freezing and boiling. Using deteriorated coolant can cause the engine to run hotter and prevent it from starting in cold weather.

How to Know If it’s Need to Change the Coolant?

During repairing or maintaining your car, check the coolant level in the sealed system and check for impurities visually. The change in color, turbidity or other properties indicates the presence of foreign additives in the coolant.

Look for these signs to determine if it’s time to clean the cooling system and change the coolant:

  • The engine gets overheated frequently, and coolant boils in the car.
  • Keep running the internal combustion engine at a crucial temperature.
  • Interruptions during turning on the hot engine.
  • A change in the rheostat’s response and the pump’s faulty operation

If you notice a color change, clean the cooling system thoroughly or replace the coolant. Despite this, if you identify this problem and drive the car for as little mileage as possible, take the car to an automobile shop.

Why Does Engine Keep Losing Coolant?

why does coolant get low

A vehicle can lose engine coolant for plenty of reasons, but the three main ones are:

  • Radiator cap leaks
  • External leaks
  • Internal leaks.

Below are some most common reasons for losing coolant along with potential solutions

Leaked Radiator Cap

A good radiator cap seals the radiator system and controls its pressure. It is critical to move the coolant and water mixture through the system in order to keep the engine cool. Conversely, a leak or lost radiator cap can reduce the pressure of the flow, making it tougher for coolant to prevent the engine from overheating. 

To diagnose this problem, read the owner’s manual, check the radiator cap, and maintain the right pressure. Alternatively, take the car to an expert mechanic.

But don’t drive your car with leaking coolant. Otherwise, driving your car despite the warning symptom will only increase the amount of engine damage and require expensive repairs. Drive your car only to the mechanic to collect coolant for leak repair, keeping an eye on the coolant level.

If you notice the coolant level is dropping too quickly, the internal coolant has suffered serious damage, and you must fix it fast. To do so, identify the coolant leak at an early stage and repair it by using K-Seal Coolant Leak Repair.

Head Gasket

A blown-up head gasket can cause severe damage to a vehicle’s engine. The coolant level can drop dramatically due to a damaged or worn-out head gasket. At some point, the coolant may also enter the combustion chamber and damage the engine block. Hence, you may notice white smoke coming out of the engine.

Faulty Reservoir Cap

A corroded or worn-out radiator cap can’t maintain the right rate of coolant evaporation. This component is mainly used to control the reserve pressure and coolant level to ensure the usual rate of coolant traveling around the hose.

If the reserve cap gets damaged, the coolant can escape and reduce the pressure inside the reserve. As a result, the dashboard may emit warm lighting. To fix or avoid it, you should change the reserve cap every couple of years and check annually for rubber or rust damage.

Cracked Cylinder Head

High temperatures and pressures can crack the cylinder head, which can cause coolant leakage. It can also damage the machine’s functioning ability.

A Damaged Radiator

The radiator is mostly made of aluminum, making it stronger yet less prone to cracking during increased engine temperature. Still, this component can get damaged and wear out due to driving the vehicle for a long time without coolant.

Even the radiator can rust eventually if you pour water rather than coolant to make the engine cool. As a result, the radiator can develop holes because of the corrosion and end up leaking coolant.

What If you are Losing Coolant Slowly?

If you notice the coolant level is dropping slowly, it’s possible your engine is losing coolant to evaporation. The engine can also lose coolant slowly if the head gasket gets blown. If so, then how do you troubleshoot to find a slow coolant leak?

A dye test and cooling system pressure test can help you out. The cooling system pressure test is the most effective method for determining the slow coolant leak.

You can hire cooling system pressure testing tools from an auto parts store at a low price. Using this tool, you can pressurize the car’s cooling system when the engine is cold and check the idle engine. This allows you to quickly and easily determine whether or not the small leak exists.

If the leak is too small to find using a pressure test, add UV dye to the coolant and run the vehicle for hundreds of miles. Then utilize a UV light to inspect for a dye’s traces. If you discover a slow coolant leak, use the coolant leak stop product to stop the leak quickly and easily.

Then keep the vehicle running on coolant to avoid buying an extra jug of antifreeze. Lots of auto parts stores sell BlueDevil Coolant Stop Leak, including AutoZone, NAPA Auto Parts, Advance Auto Parts, and O’Reilly Auto Parts.

Does the Coolant Level Drop When the Engine is Hot?

Coolant is preserved in a sealed system. If you check the coolant level in the cold engine when it’s in good condition, you won’t find any change in the level. However, if you check it in a hot engine, you’ll find the coolant level rises.

The reason is that the temperature of the engine expands the water, which increases its level, and the coolant evaporation becomes stronger. It can also cause an overflow of the reservoir and keep the coolant’s one end open. However, the level will fall back once the engine cools down.

So the coolant level drops more significantly if the engine is hot. To avoid it, you should observe and monitor the engine frequently and keep it cool. Even your coolant reservoir can become empty when the engine is hot. Instead of being worried, you should fill the engine and not drive with empty coolant.


1. Why does the coolant level drop when there is no leak?

If your car’s coolant level drops while there is no problem with an external system, the leak might leak internally into the car’s engine. Regardless, if the engine recently overheated, the head gasket most likely failed and allowed coolant to leak into the combustion chambers.

2. Should you keep the coolant reservoir full when it’s hot?

If the engine becomes overheated, it causes a breakdown and demands fresh coolant or antifreeze into the reservoir. But don’t add coolant to a hot engine. Instead, cool down the engine first and then add coolant.

3. Is dropping and rising coolant level normal?

The coolant level rises and drops along with the temperature of the coolant. It means if the tank gets hot, the coolant level will rise and then fall along with the drop in temperature. As a result, adjusting the coolant level is completely normal.

4. How often should you top up coolant?

You should inspect the engine coolant a minimum of two times a year. It’s better to perform before winter and summer. However, this recommendation may vary depending on the vehicle manufacturer. Ideally, you should top up the coolant whenever you notice the level dropping below the required level.

Final Words

After understanding how much coolant loss is normal, hope this sacrifice won’t annoy you. Instead, refill the tank with high-quality coolant that is low in density and viscosity and non-toxic before it becomes empty. This way, you can maintain the right temperature inside the engine and keep the temperature at the optimal level. Finally, don’t forget to do some troubleshooting on its related components while checking the coolant level to find out and fix the damage.