Is It Normal for Coolant Level to Drop?

May 30, 2022

Coolant level dropped.

The primary purpose of your engine coolant is to keep the engine temperature low on hot days and increase in extremely cold temperatures. But should your coolant level do down while it goes about its duties?

The answer is yes.

You should expect some drop (although minimal) in your coolant level when your engine reaches a very high temperature. Of course, there are several reasons your engine gets really hot while it’s on; internal combustion in the engine, current generation in the electric coil, continuous movement of the car’s mechanical parts, and use of the AC or heater unit.

So, when your coolant tries to combat all these heat-creating processes and keep your car from overheating, it may lose some of its water content to evaporation, which will cause the coolant level to drop. In cases like this, all you will need to do is to top up the coolant level when it gets too low.

However, this is not the only reason responsible for a drop in engine coolant levels. In a few moments, explore some other causes of coolant loss in your car engine.

But first, how much coolant should expect to drop under normal conditions?

How Much Coolant Loss is Normal?

Under normal circumstances, you should expect around a 0.25% drop in your coolant level every four to six moments. In a year, this adds to around 3 ounces. 

If you notice this, there is no need to panic. However, you should keep topping up your coolant tank regularly.

According to experts, you should expect a minimal percentage drop in your coolant level every few months. After all, your car coolant endures extreme heat conditions as it goes about its task of cooling your engine. So, it is only normal that you lose some parts of it to the heat.

Besides, every car’s cooling system is not sealed completely due to the overflow to the reservoir. So, as hot coolant moves between the primary tank and the reservoir, some coolant (minimal) will disappear as steam.

Therefore, it is good practice to refill your reservoir from time to time. Also, try and keep your radiator clean as this can help you minimize coolant loss. 

What Causes the Coolant Level to Drop Abnormally?

While minimal drops in your coolant level are not unusual, drastic changes in the amount of engine coolant in your car indicate there is a problem. Here are some common reasons you may experience an abnormal drop in your coolant levels:

Worn Out Head Gasket

Your car’s head gasket and coolant levels have a close relationship. In other words, if your head gasket wears out, your coolant levels will drop alarmingly fast. In the same way, insufficient coolant levels can also damage your engine’s head gasket.

If a worn-out head gasket is the culprit, coolant may enter your car engine’s combustion chamber, which can damage the engine block. In such a case, you may notice white fumes escaping from your engine.

Radiator Leakage

Due to the cost of coolant, some car owners may opt instead to buy lower grade coolant or even use only water in its place. Unfortunately, such decisions and liquids may corrode the walls of your radiator, which may cause leakages. When this happens, you’ll find that you can’t seem to maintain a consistent coolant level so matter how many times you fill the tank. 

Faulty Radiator Cap

Your engine’s radiator cap is responsible for maintaining an optimal flow of coolant through the hose by ensuring reservoir pressure remains adequate. However, if the radiator cap becomes faulty, the pressure in the reservoir may drop, which leads to faster coolant flow.

When this happens, you’ll experience a much faster drop in your coolant levels. Therefore, it is usually best to replace your radiator cap every two years and check it regularly for rust and rubber damage.

Damaged Radiator Hoses

Although your radiator hoses are generally heat-resistant, their close proximity to the engine (and how hot it can get) puts them at risk of damage. Over time, your radiator hoses may crack or burst, which will lead to a loss of coolant, and of course, a drop in your coolant levels.

In this case, you’ll need to replace the defecting radiator hoses. Otherwise, you risk affecting your head gasket.

Malfunctioning cooling system

Remember, your engine coolant is not the component responsible for keeping your engine temperature in safe ranges. Your radiator fan, water pump, and thermostat housing are other components that also play essential roles in cooling your engine.

As a result, if one or more of these components malfunctions, it may affect your coolant levels. For instance, the water pump is responsible for pushing coolant through your car radiator, its hoses, and the engine block. However, if the pump fails to do this, it may set off a chain of reactions that may lead to engine damage and coolant loss.

Different Scenarios of Coolant Level Drop

Here are a couple of scenarios involving a drop in your coolant level:

Coolant Level Drop Overnight

If you live in a colder climate region, it may not unusual to notice a drop in your coolant levels overnight. However, if the difference in coolant levels is extreme, then you may be dealing with an internal or external leak in your engine.

Coolant Level Drops in Cold Weather

Remember, your coolant is at least 50% water. Since water contracts in colder temperatures, cold weather may cause your coolant to contract, which causes an apparent drop in the coolant level. This is especially possible if you don’t use your car for a while and park it in a cold place.

However, in this case, the coolant level will likely go back up to its normal level once the temperature goes up or your car gets hot.

Coolant Level Drops When the Engine is Hot

Generally, it is unlikely for your coolant level to drop when your car engine is hot as the heat will cause the coolant liquid to expand thereby increasing its level. However, it is also possible for you to lose some water portion of the coolant as steam during evaporation. So, this may cause a drop in your coolant levels.

Coolant Level Drops When the Engine Revs

It is usually best not to fill your coolant tank to its maximum as the liquid expands when the engine gets hot. However, if you do, expanded coolant may spill out of the tank when you rev your engine as there is no other place for it to go. In this case, when your engine cools down and the coolant contracts, you’ll notice a drop in your coolant level due to spillage.

Coolant Level Drops Without Any Leak

If you’re sure there is no leak in your radiator or anywhere else, but you keep noticing drops in your coolant level (and none of the reasons above applies), your coolant may be escaping as steam. This is usually due to a fractured cylinder head, a blown head gasket or bad cylinder bores. So, check to make sure none of these is the issue.

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