Coolant Reservoir Empty

Coolant Reservoir Empty – Why Is This Happening?

So, have you popped open your hood and noticed how the coolant reservoir is empty? Well, don’t panic just yet, because there’s a logical explanation for this seemingly odd coolant reservoir empty problem.

The engine coolant is an essential fluid that keeps your engine in tip-top shape. Without coolant, there will be a ton of overheating issues, especially if you’re running water in your cooling system. Coolant does a much better job than water in cooling down your engine when the temperatures start climbing. As such, experiencing a coolant reservoir empty issue will likely cause the car to overheat. So, the best thing to do is to always check your fluid levels.

Another purpose of the coolant is that during winter, it prevents engine damage from freezing cold temperatures. The coolant is designed not to freeze at extremely low temperatures. This will help to take care of your engine, and will prevent the block from cracking. A cracked block will mean that the engine is now nothing more than scrap metal. So, never forget to flush your old coolant before the winter arrives.

In this article, we’re going to cover a lot when it comes to the coolant reservoir empty problem. We’ll cover all the reasons why this is happening to you. Also, we’re going to take a look at how you can fix this issue for good. So, without further ado, let’s get started.

What Do You Need To Know About Coolant?

Engine coolant or ‘antifreeze’ as it’s called by the general public is a fluid that’s used for cooling internal combustion engines. This liquid has good thermal characteristics, and can successfully transfer heat from the engine block into the radiator. By doing so, this is keeping the engine nice and cool. This is essential for the longevity of the engine.


Without proper coolant, the engine will constantly overheat. This is especially so if you’re running water in your cooling system instead. Water does not have as good of heat transfer properties as coolant, and it could result in the engine overheating more easily. The most notable reason for scrapping engines before the invention of the antifreeze was engine cracking.

Engine blocks can crack from too much heat or too much cold. When there’s too much heat, the water evaporates and creates a lot of pressure inside of the block. This causes cracks to appear, and they can lead to engine failure.

Also, in the winter there could be ice formations at below-freezing temperatures. This frosty weather will make the water inside of the engine freeze up and expand. Once again, this can result in cracks appearing in the block.

Coolant, on the other hand, has better thermal characteristics and could withstand temperatures anywhere from -34 F all the way up to +265 F. This makes the coolant an essential component of every engine.

Most of the modern coolant solutions are made out of Ethylene glycol. The coolant comes in three different colors, and each car has a different mixture of coolant. There are red, blue, green, and purple ones. When getting a new coolant for your car, it’s always a good idea to get the same color and make sure that the coolant is made for your specific make and model.

What’s The Proper Coolant Mixture?

For you to get the perfect thermal characteristics for your coolant, you need to know how to dissolve it properly. Usually, coolant comes in a concentration of 100% coolant. If you insert a 100% coolant concentrate into your cooling system, you’ll probably cause some damage to your cooling components.

The piping will start to corrode, and your cooling system will develop some issues. So, don’t do that! What you need to do is to dissolve your coolant into a 50/50 mixture. This means 50% water, and 50% coolant.

A mixture like this will make sure that the coolant inside of your engine is the right amount, balanced out with water. This 50/50 mixture won’t corrode your coolant piping and will deliver the best performance.

But you should take note that some coolant solutions on store shelves today are already bottled up in a 50/50 mixture. If you try to reduce the coolant ratio even further by adding more water, you’re going to lose some of its cooling capability. This means that the coolant will start to freeze up before it hits -37 F. Or, it could possibly cause your car to overheat.

So, always inspect the label and the directions that come with the packaging. You don’t want to make a mistake and mess up the mixture. Also, don’t forget that the color should be the same as the existing coolant in your car.

Before we dive deeper and see why the coolant reservoir empty problem appears. Let’s first learn more about what a coolant reservoir is.

What Is A Coolant Reservoir?

A coolant reservoir is a device that’s installed inside your engine bay. It’s usually located in the front and on the left-hand side, next to the radiator. Although in some cases, it can be found on the right-hand side.

The coolant reservoir is usually a white plastic reservoir. In most cars, you can see the coolant level from the outside. That said, the plastic from which these coolant reservoirs are made can oxidate over time. This can cause the orange tinge to develop on the inside, and it makes the level of coolant hard to see. However, you can always open up the cap and observe the level from the coolant reservoir cap hole.

The reservoir tank has a special purpose, and this is to make sure it relieves the pressure that’s built up inside of your cooling system. Usually, this pressure is around 15 psi. But when it goes higher, the coolant reservoir has a special hole or valve that relieves the pressure when the coolant is overexpanding.

This pressure relief system is preventing your coolant piping from exploding and thus causing a coolant mess inside of your engine bay. Also, it helps with the overall safety and robustness of your engine. Imagine if your coolant pipe explodes on the road. In this case, your engine will overheat and blow up!

As we said, in this reservoir, you can also pour the new coolant in if the amount is getting low. But what should you do when the coolant reservoir empty problem appears? Well, that situation is a bit scary. But you shouldn’t fret, because in the next chapters we’re going to explain how you can solve this issue.

How Does The Cooling System Work?

Coolant Reservoir Empty

The cooling system is very simple, as it’s basically circulating the coolant in and out of the engine. When you start your car in the morning, the coolant will be cold. It doesn’t start to circulate all at once.

The coolant will only start to circulate once the vehicle reaches its working temperature. When the vehicle reaches this right temperature, the thermostat opens and allows the coolant to flow in and out of the engine.

When the hot coolant is flowing out of the engine, it’s traveling inside the radiator that’s located in front of the vehicle. The radiator is usually located behind the front grille and is made out of many small channels that allow the coolant to pass through. As the air flows through the car from the front to back, it cools the coolant down.

Now, this cooled coolant will go through the piping, and once again ends up inside of the engine before the now-toasty hot coolant goes back into the radiator. All of this is done by the water pump which is circulating the coolant.

Next to the radiator, there is that coolant reservoir. This coolant reservoir has the min and max levels as we said, and these indicate the amount of coolant inside of the system. We use this reservoir to observe the coolant levels, and thus add new coolant if needed.

On the radiator, there are also one or two electric fans that start spinning when the atmosphere rushing through isn’t strong enough. Plus, the radiator needs some extra cooling to keep the engine temperature in check. As we mentioned earlier, the cooling system is pretty straightforward. This system consists of coolant hoses, a radiator, some fans, a thermostat, and a water pump.

Reasons Why Coolant Reservoir Empty Problem Appears

If you have a coolant reservoir empty problem, then you most likely have an issue with your cooling system and are going to need to check these components that we mentioned before. These parts are the thermostat, hoses, radiator, cooling fans, and water pump. In this chapter, we’re taking a look at all of these units, as well as the possible reasons why they can cause this coolant reservoir empty problem to appear in the first place.

1. Broken Radiator Cap

One of the simplest reasons why this fault can appear is a broken radiator cap. This cap is more complicated than you might think. It keeps your cooling system pressurized at 15 psi. If it goes higher than this pressure, a small vent on the cap opens up and relieves the pressure. This is where the problems lie.

This cap knows when there’s a malfunction, and can learn to stay open. This causes the coolant to evaporate into the atmosphere. Nevertheless, the more your coolant evaporates, the less coolant you’ll have in your cooling system.

So, when you’re having an issue with loss of coolant, it can potentially result in your engine overheating, as well as causing some damage to the engine. Fortunately, these radiator caps are pretty cheap, and you can get one for a few dollars from your local parts store. If the problem persists, then it’s time to take a look at some of the other components inside the cooling system.

2. Coolant Hose Leak

car oil leak

Coolant hoses tend to leak, especially if there’s a lot of pressure due to overheating. This overheating can increase the pressure and make your hoses bloated. Moreover, the pressure can cause the clamps that are holding the hose in place to expand and possibly snap.

If a clamp snaps or stretches, then the coolant will slowly start to evaporate and disappear. This problem is fairly simple to diagnose and repair. All you need is to just get under the car, and see where the leak is coming from.

A leaky hose can be tightened with a new clamp. These clamps come cheap and don’t cost more than a few dollars. But if your cooling hose is bad, then you’ll have to replace the entire hose. Hoses can be costly, and you can find them selling for around $50 or more, depending on the make and model of your vehicle.

Also, it’s a good idea to check the head gasket. Usually, these head gaskets, when they leak, tend to also damage the hoses.

3. Hole In The Radiator

A hole in the radiator is also a probability, especially if it’s an old radiator or a radiator that’s been damaged in an accident. Old radiators tend to leak more often because of the amount of corrosion built up inside of them. This causes the coolant to seep through holes and escape.

How you can spot a leaky radiator is fairly simple. You need to get under the car and see from where the coolant is leaking. If nothing appears, then the hole is small, and it’s like that the coolant has evaporated. This will require the removal of the radiator, and conducting a smoke test.

If there is smoke flowing out of the radiator, then you know that you’re dealing with a hole. Therefore, this hole needs to be patched up. Patching it is fairly cheap and easy. There are plenty of shops that repair these radiators for relatively little cost.

But the best fix is to replace the radiator with a new one. A new radiator will make sure that you don’t have any more leaks, and that your system will cool much better than it used to. This will make your car more drivable and could save you a lot of money in the long run. Also, radiators aren’t that expensive, and you can snatch one for around $150.

4. Bad Water Pump Seal

A bad water pump seal may also cause you to lose coolant. This seal is responsible for keeping your water pump in place. The seal is usually made out of rubber, and over time, it can harden and crack. This causes coolant to start leaking from it.

If you are having a coolant reservoir empty issue, it’s a good idea to inspect the water pump for any possible leaks. If there are any, then it’s best to replace the seal. Since you’re replacing the seal, it’s also a good idea to replace the water pump altogether.

In the long run, it’s going to be cheaper for you because a water pump service is recommended after 60,000 miles. So, if you’re near that mileage, then grab a new water pump to replace the old one. A new seal won’t cost you a lot.

Although, the labor costs will be high as it requires the removal of many components plus the water pump. That’s why doing the water pump service while you’re replacing the seal makes a lot of sense.

5. Blown Head Gasket

A blown head gasket is probably one of the issues that you don’t want to have on your car. Head gaskets can be a pain, to be honest. So, it’s best to stay away from engines that are prone to head gasket failure.

A blown head gasket causes the coolant to escape and enter into the combustion chamber or the oiling system. If the coolant gets into the combustion chamber, then you’re going to have some white smoke coming out from the exhaust system.

This white smoke is caused by the evaporation of the coolant. If the coolant gets into the oil, you’re going to have some sludge into your oil. This sludge will turn your oil thick, and thus it can’t lube the engine components properly.

In both cases, you’ll have a coolant reservoir empty problem. This reservoir will start to drain once there are some holes in the gasket, and the car starts losing coolant. If the car keeps losing coolant and you don’t fill up the coolant reservoir, the car will tend to overheat.

These overheating issues will damage your engine. The most notable outcome from running your car with a blown head gasket is a bent engine head. The engine head will start to warp from all of the heat. If a head warps too much, then it’s probably trashed.

The best thing you can do will be to get a replacement head. If it’s not bent too much, then a simple resurfacing of the head will do the trick. A blown head gasket repair can be expensive. This could easily set you back $1000 if your engine head needs too much machining work.

What To Do When You Are Having Coolant Reservoir Empty Problem?

If you’re facing this issue, it’s a good idea to monitor the coolant level and fill it up whenever needed. If you lose a little coolant, then you won’t have to worry too much. In this case, try replacing the coolant tank cap. Coolant tank caps are pretty cheap and you can easily find a replacement.

If this doesn’t help, then the best thing for it is to look for leaks. Make sure that you inspect all the clamps that are holding the hoses. If a clamp is leaking, then replace it with a new one. A new clamp will only cost you just a few dollars.

Also worth checking out is the water pump and radiator. Make sure that no coolant escapes from the water pump. It needs to seal properly. If the water pump is leaking, then the best thing to do is to replace the water pump and thermostat altogether.

Should a leak be coming from the radiator, then inspect the radiator and patch up the hole. If the radiator is too old, then you should have it replaced. Also, check to make sure that coolant doesn’t just come from anywhere else.

If you have dirty oil mixed in with coolant, or your car produces white smoke, then for sure, it’s the head gasket that causing this issue. In this case, you’ll need a new head gasket and a head resurfacing. A good resurface will make sure that your engine head is brought back to life and is going to seal properly. This is also an expensive repair but it is what it is.

Is It Safe To Keep Driving With A Coolant Reservoir Empty Problem?

Driving like this can be safe for a little while until you figure out what are the next steps in your repair process. But be wary to never let the coolant reservoir empty issue appear in the first place. If you leave it completely empty then your car will be left without enough coolant, and this will cause your engine to overheat.

So, be sure to monitor the coolant level. If your car is losing too much coolant too quickly, then park up the car and don’t drive it. This will make sure that your problem does not get any more serious than it really is.

Book an appointment with your local mechanic and do a thorough inspection of your vehicle. With a good mechanic and a detailed inspection done, you’ll be more informed about what the real culprit is, and how to handle this issue properly.

Coolant Reservoir Empty – Conclusion

In this article, we’ve covered a lot when it comes to the coolant reservoir empty problem. We learned about the basics… What is coolant, what is a coolant reservoir tank, and where is it located? These are things that you have to know in order to learn more about what you need to troubleshoot.

Then, we have explained how the cooling system works, and what are the main components of this system. These were, as we detailed, the thermostat, water pump, hoses, radiator, radiator fans.

And lastly, we’ve covered all the reasons why your coolant reservoir empty appears and these were: bad coolant reservoir cap, loose clamps, bad radiator, and broken head gasket.

We’ve now learned everything that you need to know when you’re dealing with this coolant reservoir empty issue, and what your next steps will be.

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