Cooling System

7 Symptoms Of A Failing Cooling System

Daniel McDonald
Daniel McDonald7 min read
7 Symptoms Of A Failing Cooling System

A vehicle’s cooling system plays a big part in the engine’s proper functioning. It helps engines maintain the optimal temperature and prevents overheating. Thus, the cooling system must be working correctly 100% of the time.

There are a few basic signs that indicate a failing cooling system. Keep reading to find out the seven symptoms of a failing cooling system!

High-Temperature Reading

If you notice that your temperature gauge is rising and entering the red zone, the coolant system is failing, and you need to stop the car. If you do not pull over, you risk the engine overheating, damaging your vehicle.

Once you notice this temperature spike and the temperature gauge going into the red zone, call your mechanic and ask for advice. He will know exactly what you should do and whether or not you should drive your car or tow it.

Low Coolant Levels

The coolant is the most crucial part of the cooling system. It is what cools down the engine and prevents overheating. So, having the exact right amount of coolant in your car radiator is essential. We advise you to check the coolant level every time you enter your vehicle.

This way, you will constantly have control and won’t risk causing damage to the engine. If the coolant levels are low, it can mean two things. Either you need to fill the radiator tank with more coolant or look for a leak.

If you regularly check the coolant levels, you can quickly know the difference and determine whether you need to add more fluid or take the car to the mechanic.

If the coolant level is constantly low, or it goes down extremely quickly, there is a high chance that somewhere in the system, there is a leak.

Constant low coolant levels are a bad sign, so if you notice this, do not hesitate to contact your mechanic.  

Weird Coolant Color

Just keeping an eye on the coolant, you can easily find out if there is anything funny going on in the cooling system.

Look at the coolant color; a regular, healthy coolant has light green or yellow coloring. In some cases, the coolant can even be translucent.

Your cooling system fails if the coolant is darker or filled with dust particles. When you notice the discoloration in the coolant, you should change and flush it thoroughly; or, in some cases, switch some components of your cooling system.

Coolant Leaks

As we mentioned, the coolant is an excellent indicator of the state of the whole cooling system.

By checking the coolant, you can see if something is wrong with the system. Pay attention to any fluid leaks when your car is not moving.

Inspect the driveway and look for a bright or green liquid underneath your car. If you find a leak, call your mechanic, and ask for advice.

In some cases, the leakage can be yellow or pinkish; anyhow, if there are coolant leaks, your cooling system is not working correctly.  

Smoke From The Hood

Pretty obvious, right? Smoke from the hood is never a good thing. This is a widespread symptom of a failing cooling system. If you notice smoke coming out, there is a chance that the vehicle is overheating.

This is a sign that you need to stop the vehicle immediately. If you continue driving while smoke comes out of the hood, you risk cracking the engine block or having a blown head gasket.

Hence, to avoid damage to the engine block, the pressure cap, or the cylinder head, you should take precautionary measures to keep the engine away from excessive heat.    

Exhaust Smoke Is White

The coolant burns inside the combustion chambers if the exhaust smoke looks like a white and puffy cloud. If this happens, you may have a broken cylinder head and an internal leak.

The white exhaust smoke is a severe symptom of a malfunctioning cooling system, and it may even mean that the engine needs to be rebuilt.

Warning Lights And Decreased Gas Mileage

A warning sign is the most obvious indicator of something wrong with the vehicle. The engine cooling system works if you notice a warning light on your car dashboard and the temperature gauge shows very high readings.

When the gauge enters the red zone, it triggers a warning light to show you that something is incorrect and the engine is at risk of overheating. If you notice any warning lights on your dashboard, call a mechanic and ask him for help.

Another severe symptom of a failing cooling system is decreased gas mileage. Every car has its optimal engine temperature in which it reaches maximum efficiency.

However, the gas mileage will start reducing if that engine temperature exceeds the optimal level.

A decreased gas mileage indicates that the cooling system is failing. Take your car to a mechanic before you cause engine overheating.  

Problems That Cause Cooling Systems To Fail

Many different things can cause the failure of cooling systems. Let’s examine them one by one!

Leaks In The Radiator Hoses  

The engine in your vehicle is connected to the radiator and the water pump via rubber hoses. These rubber hoses are called radiator hoses and help the coolant flow from the water pump to the engine and from the internal combustion engine to the radiator. They work as a heat ex changer and allow coolant expansion.  

If a radiator hose leaks, the coolant will not flow throughout these three elements as it should. When the coolant circulation is improper, the vehicle will not cool down and absorb its extra engine heat. Hence, the radiator cap can fail to cause the engine to overheat.

If you know which radiator hose is at fault, you can buy a new one and replace it. It would help if you observed the radiator hoses once in a while to protect the cooling system from fluid leaks.  

Water Pump Collapse

The water pump is essential in the coolant flow process. It is driven by the engine power and helps the coolant reach the engine to prevent overheating. As we mentioned, the water pump is one of the three main elements circulating the coolant throughout the engine vents.

When the water pump is damaged or faulty, it cannot enable good coolant flow, and the engine will quickly overheat. To prevent this, you should promptly examine the water pump once in a while. If you notice cracks or faulty parts, you should replace them with a new pump.

Of course, if all this sounds overwhelming, you should take your vehicle to a car service.  

Read our ultimate guide to water pump replacement.

Frozen Coolant

Since water freezes below 0 °C, it can create a huge problem inside the cooling system. Every time the weather outside is cold, you risk the coolant freezing and causing the failure of the coolant system.

So, keep this in mind if you park your car in a cold place. The coolant is mixed with water, and water can quickly freeze. If the coolant is frozen, it will fail the entire cooling system, and your engine components can get damaged once you start the car.

Check the coolant before driving the vehicle if you live in a place where the temperature drops below 0 °C. If you see that the fluid is frozen, start the engine and wait a couple of minutes for the coolant to turn liquid. After that, you can safely drive the vehicle.


Malfunctioning Thermostat

Another problem that occurs within the cooling system is a broken thermostat. A working thermostat regulates the temperature inside the engine and holds the coolant that flows throughout. It is a mechanical component that acts like a valve; it opens and closes, allowing the coolant to pass.

After the engine is warm, the thermostat will fully open to allow cooling. If the engine is cold, the thermostat remains closed, which helps the engine to reach the optimal temperature.

Thus, a fully functioning thermostat is essential! A properly working thermostat enables the coolant to flow and keeps the engine from reaching a boiling point. If the thermostat is damaged, it can cause severe damage.

If you notice that the thermostat is malfunctioning, you should replace it.

Malfunctioning Temperature Gauge

The temperature gauge shows the engine’s temperature on your car’s dashboard. If you cannot see the temperature, it will be difficult to notice if there is any damage in the system.

An accurate temperature reading is essential. Therefore, if you see that the gauge is malfunctioning, you should repair or replace it. There is a simple method to check if the temperature gauge is faulty.

Use a thermometer to measure the temperature inside the water tank and then see the readings in the temperature gauge. The temperature gauge is broken or failing if the numbers are pretty different.


The cooling system is a vital part of one vehicle; it keeps the engine from reaching the boiling point. So, the cooling system must constantly be working correctly.

To ensure that, you can schedule regular mechanic visits and take your car to get services at least once a year. In the meantime, you should do check-ups to ensure everything is working correctly.

Suppose you notice any smoke coming from the hood, high-temperature readings on the temperature gauge, white exhaust smoke, weird coolant color/coolant leaks, or warning lights. In that case, you have a failing cooling system and need to contact a mechanic immediately.


What Is The Main Cause Of Cooling System Failure?

If the cooling system fails, the engine will overheat. While many factors can cause a coolant system failure, a coolant leak is the main and most common one.

How To Know When The Thermostat Is Failing?

If the thermostat in your car is failing, you will get high-temperature readings or sudden temperature changes. Also, you may notice some coolant leakage, strange noises, or increased fuel consumption.  

How To Check If The Coolant Is Circulating Properly?

To check if the coolant is circulating as it should, you should start the engine and let it idle. Then look at the radiator filler neck and see if the coolant circulates.

Since your car has not yet reached the optimal temperature, the thermostat should be closed, and the coolant should not flow throughout the engine.

If you notice that the coolant is circulating, there is a problem with the thermostat since the valve is wide open for the coolant to circulate.