Coolant Reservoir Full But Radiator Empty: Why And What To Do?

The cooling engine of every vehicle has a vital part in the regular and efficient operation of the engine in all automobiles. A lot of people ask why their coolant reservoir is full, but their radiator is empty. So this article will focus on the reasons, signs, and solutions if your coolant reservoir is full, but your radiator is empty. 

So why is your coolant reservoir full but your radiator is empty and what can you do about it? If your coolant reservoir is full but your radiator is empty, there might be something wrong with one or more in the components of your engine cooling system. There are a lot of possible things that you can do, you just have to know the reason for it. 

Many car drivers have been complaining and asking why their radiator is empty but they have a full coolant reservoir. Some car drivers already know the answer and they also already know the reasons for it. 

However, there are some car drivers who are still unaware about it and they do not know what to do about it. We will talk more about how to fix this issue and what causes it. 

With this article, car drivers will be informed about this issue. Let us get started. 

Coolant Reservoir Full But Radiator Empty

Why Is My Radiator Empty When The Coolant Reservoir Is Full?

The function of the liquid cooling system is to transport the coolant through a passage in the engine blocks and the heads. The coolant will then pick up the heat while it passes into the engine. If the coolant is heated, it will then flow into the radiator through a rubber hose. 

The heated coolant will then move through a thin tube in the radiator. It will cool down by the airflow coming to the engine compartment of the vehicle’s grill. With that, the liquid will then cool down. 

It will then flow back into the engine so that the temperature will be reduced. If your radiator is empty but your coolant reservoir is full, it can mean that there is one or more than one problem with the components of your engine cooling system. This will mean that there is a possible fault in the radiator or your radiator hose. 

You might also have a damaged gasket, a damaged radio cap, or some damage to other components. If you have this problem, you have to tighten the hose clamp. Next, fill up the radiator with a coolant because it will be pretty standard for the coolant level of the radiator to decrease over time. 

If you have done this, you will notice a significant decrease in the level of your coolant. With that, it makes you sure that you have a damaged component. You will also have to bring your vehicle to a mechanic.

Does Coolant Flow From Reservoir To Radiator?

Yes, the coolant does flow from ther reservoir and into the radiator. But suppose the overflowing coolant reservoir will not return to the radiator. In that case, it might mean a leakage or a clog in the radiator hose that gives access and passage to the flow of fluid to the radiator from the coolant reservoir. 

This can also be a result of a damaged radiator cap. So if you have a damaged radiator cap, this will allow an escape of the coolant into the radiator. As a result, the coolant will not return to the reservoir. 

Does The Radiator Need To Be Full?

The radiator reservoir is also another essential component of the engine cooling system. The radiator reservoir is a vital component, and it must reach a top line because it is where the new and fresh coolant will be poured into the cooling system. The radiator reservoir is the one that will store the excess coolant until the temperature of the engine reduces it. 

If you have a low radiator reservoir, it will make your engine overheat. This means that you have to check the level of your coolant regularly. 

Is It A Problem When The Radiator Is Empty?

Yes, it can be. If your coolant reservoir tank is damaged or you might have a leak due to overheating, it can cause the coolant to drip from the coolant reservoir and empty the radiator. If you have a damaged reservoir tank, it will cause evaporation of the coolant, and it might also cause the coolant reservoir to fill up. 

The drop rate in the level of the coolant will also depend on the extent of the damage. The level of the coolant will then decrease over time.

empty car radiator

Signs Of Coolant Reservoir Full But Radiator Empty

So if your coolant reservoir is full, but your radiator is empty, these are the common signs you will experience. 

1. Your Engine Will Start To Overheat

This is a prevalent sign, reflecting that there is something wrong with your cooling system. This can be because of a damaged or faulty radiator, or you might be having a bad thermostat. There might also be some other related issues. 

If you have this problem, it can significantly reduce the operation of your vehicle because of the poor performance of your engine. The engine will overheat, and it will start to produce smoke. Soon, you will have a vehicle breakdown. 

2. Your Heater Will Start To Malfunction

If your heater is not functioning, this can be a sign that you do not have enough coolant in your radiator. This is because the heater will depend on the hot fluid, and it will flow through the core. If the hot fluid flows, it will then release hot air and blow into the vehicle. 

3. Your Coolant Will Start To Leak

This is another sign that you have no coolant in your radiator. You will start to notice that your coolant is leaking from under your vehicle. It can drop from the hoses or the radiator.

 The coolant level of the radiator will become low if it has not been punctured or completely damaged. This can cause the engine to overheat.

4. There Will Be A Discoloration In Your Coolant

If you have no coolant in your radiator, it can cause the coolant to change in color. The coolant of the vehicles is primarily yellow, pink, or green. 

This can become a thick brow if there is contamination. This will obstruct the flow, and it will clog the radiator. 

5. Your Engine Check Light Will Be Illuminated

If your radiator has no coolant, there is a high increase in the engine’s temperature, which will make the engine check light on. The driver will know that there is an issue. It should be fixed so that you can prevent further damage to your vehicle. 

6. There Might Also Be A Persistent Odor

You will have a sweet smell around your vehicle or inside your vehicle. The smell of the coolant is sweet. If you smell something like that, there might be a leak in your coolant. 

7. You Will Have Smoke In Your Engine.

If there will be a release of white smoke from your car’s exhaust, it means that the coolant level of your radiator will be shallow, and you must refill it. 

How Do You Fix This Issue?

If your radiator cap is damaged, then you will need to replace the damaged radiator cap. If you can do it yourself, you can perform this task. Just ensure that your engine has cooled down and you have bought the right and suitable radiator cap for your vehicle. 

You can consult a mechanic if you do not know how to do this. And if you have worn-out or torn radiator hoses, you have to park your vehicle on dry ground and then let your engine cool down. Allow your vehicle to rest for a couple of hours.

And then, you can investigate if there is any leakage of coolant under your vehicle. Check if there is liquid dripping down. You can tighten the hose clamp if there is any leakage, and you might need to replace the entire radiator hoses. 

If your radiator or water pump is not suitable for your vehicle, you must bring your vehicle to a mechanic shop. You need the help of an expert. If there’s a blown head gasket, you need to decide if your head cylinder is worth fixing because this can be very expensive. 

Fixing this issue includes costly components. If your manifold gasket is faulty, then the mechanic will change the component, and it can already be resolved. If there’s no coolant in your radiator, you will need to refill the radiator with a coolant. 

The level of the coolant of the radiator will decrease over time. You need to monitor this. If there is a single drop of coolant level of the radiator, have your vehicle checked.


In summary, the cooling reservoir and the radiator is an essential component of a vehicle. A lot of car drivers have been experiencing a full coolant reservoir, but their radiator is empty. 

With that, many car drivers have been asking about the causes and the solution. There are solutions to every cause above. Read the article as your reference.

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Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more