What To Do When Car Ran Out Of Coolant And Won’t Start

Coolant is a liquid that is used to prevent the engine from overheating. It also prevents friction between the moving parts of the engine. But sometimes the car may run out of coolant and not start. 

When the car doesn’t start because of low coolant levels, check the coolant level and add coolant. You may also need to change the coolant if it is too old. Low coolant or no coolant in the system may also have more reasons and fixes. 

So, this article will cover the possible fixes, symptoms, and causes of why a car runs out of coolant. Also discuss how you can solve the issue if your car doesn’t start when the coolant level is low.

car ran out of coolant and won't start

Symptoms Of A Car Running On Low Coolant

The coolant level can be lower for various reasons. But when it is, you may experience several symptoms. However, the following would be the most common symptoms: 

The engine gets overheated

engine gets overheated
engine gets overheated

An overheating engine is the most common symptom of a car running on low coolant. Enough coolant in the reservoir is mandatory to run the cooling system properly. 

If the coolant level is lower than its requirement, the system will fail to control the heat, and the engine will overheat.  

The dashboard warning light is illuminating

warning light is illuminating
the warning light is illuminating

There is a temperature gauge injected inside the engine compartment. It measures the engine’s temperature and sends the reading to the dashboard.  

If the coolant level gets lower, the temperature starts rising. When the temperature reaches an alarming rate, the dashboard light turns on. 

Sweet or burning smell

The coolants used in the cooling system have a sweet smell. So, if the coolant leaks inside the system, it will spread a sweet odor. 

The leaking coolant can also burn due to the extreme heat. So, you can get a burning smell from under the hood or ventilation area. 

Low fuel efficiency

Low fuel efficiency
Low fuel efficiency

As we said before, the cooling system helps the car’s engine work properly. If the coolant is low, the temperature starts rising. 

Thus, if the engine becomes overheated, it will consume more fuel. It is called low fuel efficiency.

The reservoir is overflowing

If the radiator cap is not sealed properly, it can cause the coolant to overflow into the reservoir. Thus, if the coolant reservoir overflows, it will reduce the coolant level in the system.

The engine turns off

If the coolant in the cooling system is too low, the engine can turn off automatically. The engine can also start stalling.

It occurs when the engine is too hot because of a lack of coolant in the radiator. The rising temperature can also completely damage the engine; thus, the car may stop starting. 

Possible Causes Of A Car Running Out Of Coolant

The key reason why a car runs out of coolant is because of leaks in the cooling system. These leaks will result in low coolant in the radiator. The other possible reasons for a car running out of coolant are listed below:

Faulty radiator cap

Radiator caps are often open and closed. If it is not properly sealed or left loose, it can cause the coolant to leak. 

A radiator cap can also be faulty or broken when it gets too old. A broken radiator cap can also cause the car to run out of coolant. 

Radiator leaks

A pinhole leak in the radiator can cause the coolant to leak. It occurs when the radiator is worn out or is not properly set. 

Leaks in the water pump

The water pump is designed to store and secure the coolant. To do so, it uses several gaskets and seals to keep the coolant engaged. 

If these gaskets or seals get loosened, worn out, or cracked, the coolant will leak and lead the car to run out of coolant. 

Hoses leak

A series of hoses circulate the coolant to the engine block. But these hoses and tubes can be corroded over time. Unfortunately, if it occurs, the coolant can leak through these damaged hoses.  

Extreme cold or hot weather

Weather conditions also have a great impact on the radiator fluid. If the weather outside the car is too cold or hot, the density and volume of the coolant can be reduced over time. 

Can Coolant Prevent Your Car From Starting?

Normally coolant doesn’t prevent your car from starting directly. But if you continuously drive without coolant, it can destroy different parts of the car. 

No coolant in the cooling system causes overheating in the engine compartment. It leads the cylinder and pistons to melt and bend together. 

Thus, it seizes the engine, and a seized engine can never be repaired. A car running out of coolant can damage various parts of the drivetrain. When these circumstances happen, the car will face difficulties getting started. 

What To Do When Your Car Won’t Start Because It’s Out Of Coolant?

A car won’t start for a variety of reasons. Here are a few things you can do when your car won’t start because of no coolant:

Minimize the temperature

As the engine can die because of overheating, the first thing to do is reduce the temperature. So, pull over to a safe location and wait for the engine to return to normal operating temperature. To monitor the temperature, check the temperature gauge. 

Add coolant

When your car is out of coolant, you must add more coolant to the system to increase the coolant level. If you don’t have the coolant in your car or are far away from repair shops, you can use fresh drinking water as radiator fluid.  

Restart the car

You can restart the car and take it to a repair shop if the engine becomes cool enough. But if it still refuses to start, the engine or other part of the engine compartment has become damaged and needs to be replaced. 

How Can I Prevent My Car From Running Out Of Coolant In The Future?

Here are the precautions you can follow to prevent the car from having low coolant in the future

  • Monitor the cooling system regularly to find leaks.
  • Check the coolant level and add more coolant if necessary.
  • Change the coolant if it is too old. 
  • Check and replace the radiator cap if it is damaged.
  • Seal the radiator cap properly. 
  • Check the hoses and gaskets to see if they’re loose or need to be replaced. 

frequently asked questions

Now we know what to do when a car is out of coolant. Here is more information to know better about it:

How Often Should I Check And Refill The Coolant In My Car?

You can check the coolant once a month, as the level will remain the same if there are no leaks. But you must check for leaks regularly and change the coolant at least twice a year. 

Is It Okay To Use Water As A Temporary Coolant Solution?

Yes, it is okay to use water as a temporary cooling solution. When it’s an emergency, and you don’t have any antifreeze solution, water can be helpful to protect the engine. 

Can A Car That Has Run Out Of Coolant Experience Engine Overheating?

Yes, a car can experience engine overheating if it has run out of coolant. The coolant allows the engine to function properly and protects it from overheating. If there is no coolant, the engine’s temperature can’t be regulated, and it becomes overheated. 

Is It Safe To Mix Different Types Of Coolant In My Car’s System?

No, mixing different types of coolant in a car’s system is unsafe. In an emergency, you can use water or any other temporary coolant. But you should change it and clean the system before adding the right coolant. 


Now we know why a car experiences low coolant and won’t start when it’s out of coolant. As the possible reason is leaking, always be careful about unexpected leakages in the cooling system and engine compartment.

But unfortunately, if the coolant level becomes low and the engine gets too hot, don’t panic. Shut off the car and let the engine cool down. Then check the coolant level and add the necessary amount of coolant.

However, never drive your car with no or low coolant in the system. As we discussed before, it can lead to the car too expensive damages. 

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