Coolant Reservoir Empty But Not Overheating (3 Reasons)

You’ve installed a coolant reservoir on the engine of your car. Because it keeps your engine cool. But you suddenly notice that the coolant reservoir is empty without being overheated. 

But why is the coolant reservoir empty but not overheating?

Well, there are 3 main reasons behind this issue. Firstly, a hole in the radiator could be the problem for this issue. Not only that but a bad radiator cap can also cause this problem. Finally, a faulty water pump can also be a culprit for this issue. 

You need some time to get the entire part. So, spare some time and read along!

3 Reasons for Your Coolant Reservoir Being Empty

We’ve already got the gist of the reasons for this issue. So, the reasons are given below in detail along with the solutions:

Reason 1: Hole in the Radiator

Your car’s radiator is obviously critical to the cooling system. It’s also under a great deal of strain almost all of the time. As a result of this, it may experience normal wear and tear. Corrosion can also build up inside the radiator.

This could eventually result in it developing a hole. For this reason, your car’s coolant will most likely flow out when this happens. Thus, the coolant becomes empty without being overheated. 


Now, you might consider having a look at your automobile to find out the problem. But eventually, you’d need a mechanic to look after it. 

There are numerous hoses that run into and out of your radiator. But it only takes one faulty connection to cause a coolant leak. So, a professional will be able to refill your coolant reservoir by repairing your radiator.

Now, you might not be sure which hose to use for this:

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Reason 2: Bad Radiator Cap

In the big scheme of things, your car’s radiator cap is involved. In comparison to many other parts in autos, this is a little important. However, if your coolant reservoir is empty, it could be the cause. Because it performs a crucial function. 

As a result, the radiator in your car will be compressed. This indicates that the seal is created by your radiator cap. 

But this task was to be done by the coolant reservoir. It may also cause coolant to leak out of your vehicle if it becomes malfunctioning. As a result, your coolant reservoir will be empty.


Well, there’s some good news. That is, replacing the radiator cap on a car is a fairly simple job. It won’t cost you much either. But don’t forget to take help from the experts for this.

But there’s also bad news. That is, not everyone realizes they are holding a bad radiator cap. Therefore, check if the radiator cap is faulty if you notice your coolant reservoir is empty.

There are few symptoms of a faulty radiator that are enough to assure you about the issue.

Moreover, you can also consider checking the coolant reservoir. Not sure which radiator cap is the best to use? 

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Reason 3: Faulty Water Pump

The majority of people are aware that their car has a water pump. However, they frequently have no idea what it’s for. There is anything a water pump is in charge of. That is, maintaining the coolant in an automobile circulating. 

So, your water pump typically sits someplace close to the lowest of your engine. It has a hose that connects to your radiator. It guarantees your coolant is capable of passing through your cooling system. So, eventually, your coolant reservoir goes empty.


The hose is utilized by the water pump to ship coolant to the radiator. But this may get corroded or preserve different varieties of damage. While that happens, the coolant reservoir begins to drain out pretty soon. 

Thus, you need to change your water pump. As a result, it would forestall coolant from leaking from your car.

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Frequently Asked Questions

Why is the coolant reservoir empty even though the radiator is full?

The overflowing coolant reservoir occasionally does not return to the radiator. This indicates that the radiator hoses may be leaking or clogged. Fluid may flow from the coolant reservoir to the radiator as a result. A malfunctioning radiator cap could possibly be the cause.

Does the car overheat if the coolant reservoir becomes empty?

Without coolant, there would be a lot of overheating issues. Mainly, you experience this if you run water through your cooling system. Coolant works much better than water to cool your engine. Therefore, an empty coolant reservoir can cause the vehicle to overheat.

What if I overfill the coolant reservoir?

Coolant expands as it heats up and contracts as it cools. Thus, the extra space prevents damage to your engine and pipes. Overfilling the antifreeze tank can cause electrical damage if the situation escalates. But it will happen if the spilled water comes in contact with the motor wiring.

Is it okay to add coolant to the reservoir if the engine is hot?

When the engine is heated, you can’t add coolant to the reservoir. There are cases when the engine overheats, causing problems. Therefore, it may be necessary to add new cooling antifreeze to the cooling system. However, you must not add coolant if the engine is hot. Instead, you need to wait so that it cools down.

Final Words

Now, you know why is your coolant reservoir empty but not overheating! We tried our best to explain the reasons simply. 

Don’t forget to reach out to us for any queries regarding automotive!

We wish you all the best in your automotive!

Rob Dahm

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