How Much Coolant Should Be In The Overflow Tank?

As a car owner, it is essential you know the works of the coolant in your car. Coolants are the toxic liquid that goes into your car’s reservoir to keep the engine running at an optimal temperature without blowing up your head gasket. However, overfilling this liquid has its adversaries.

Are you trying to know how much coolant should be in the overflow tank, or you’re asking should there be coolant in the overflow tank at all? In this article, we’ll discuss at length and even show you the amount of coolant loss that will significantly affect your engine’s performance.

How a coolant reservoir works

Many car owners have a general knowledge of how a car works. But do they also know how a coolant reservoir works? A coolant reservoir plays a major role in ensuring your car runs smoothly. A problem with this component (like no coolant in the radiator) can cause severe damage to your engine system. Therefore, it is recommended that you know the work of a coolant reservoir tank and how to figure out issues with your reservoir tank.

should there be coolant in the overflow tank

As your engine burns fuel to power your car, it generates a tremendous amount of heat. If this heat gets to a certain level, it causes severe damage, like cracked cylinder walls and blown head gasket to your engine. This can cause your car to stop at any time. Although these damages can be repairable, it causes you to pay for hours of labor.

Your car’s cooling system’s sole aim is to extract heat, keep your engine at an average temperature, and prevent these types of damages. The cooling system circulates coolant to your engine through a water hose and pipes surrounding your engine. Thus, the extracted heat from your engine converts it into gas and sends it back to your radiator – converting it back to a liquid form. During this process, the radiator sends the extracted heat outside your car.

As your car’s temperature rises to a certain degree to release pressure, the spring in your radiator cap expands, which in turn, allows your coolant to escape straight to the reservoir tank. This coolant stays in the reservoir until your engine cools down and requires more coolant from the reservoir tank to continue the circulation. So, you might ask, how much coolant does my car need when empty? Your coolant reservoir tank should be at least 30% full. Most reservoir tank has a minimum and max mark drawn on the side of the container.

The most common cause of a coolant leak is a bad radiator cap,  bad radiator fans, and loose radiator hose clamps. So, is it normal for the coolant level to drop? Yes, due to the degree of a running engine temperature, a small amount of coolant tends to drop through vapor. A leak means that the stored coolant is dripping out, which will eventually cause a low coolant level. To prevent engine overheating, ensure you check your radiator and coolant level regularly. If you notice your temperature gauge is going high while driving, you have to pull over and turn off your car. And allow your engine temperature to cool down. Check your coolant and inspect if there are any leaks.

How much coolant should be in the overflow tank?

A coolant reservoir, also known as an overflow tank, is a container that stores overflowing or excess coolant. It is usually a transparent plastic container close to your radiator. The overflow itself is where the coolant is poured directly and not into the radiator, as most people think.

how much coolant should i put in my car

As I have outlined, engine coolant removes excess heat from the inside of your engine. Coolant is a mixture of water and antifreeze. If the coolant level becomes too low, it produces excess heat, which could cause damage to your engine. You might ask how much coolant I should put in my car. Read on. I’ll explain this in simple terms. Checking your coolant level is very simple.

Once your bonnet is open, you need to locate your coolant overflow tank. A water hose is connected to your radiator close to the radiator cap that connects to the overflow tank. It is relatively easy to find. The coolant inside can be green, yellow, pink, orange, red, or gold color. Do not take a wiper reservoir for the coolant reservoir. On the body of the overflow tank, you will find two marks, Full and Low. These lines tell whether the coolant is low or high. If the coolant is below the low mark, you have to add more coolant to the reservoir.

Before you add extra coolant to the overflow tank, it is imperative to make sure the engine isn’t hot. If the engine is hot, there could be pressure in the reservoir, and if you try to open it, it can split out and cause you severe injury. Make sure there isn’t any pressure trapped in it.

To open your reservoir or radiator, place a rag on the cap while opening it to ensure water doesn’t split on you. The coolant amount that should be in the overflow tank has to be on the full level – this connotes the coolant is at maximum level. If you’re asking, how much coolant should be in my radiator? Unlike the overflow tank with a full and low level indicating when the coolant is low or overfilled, the radiator does not have minimum and maximum levels. You just have to fill your radiator to the brim.

Read Also: Best Antifreeze Tester Reviews

Frequently Asked Questions (FAQs)

When Should I add coolant to my overflow tank?

If you notice the coolant level is low when cold, you have to too up the coolant. Or notice the car running hot; you have to turn off your engine. Allow it to cool down. It will take your engine one to two hours to cool down. Once your engine is cool, open your radiator and overflow tank, and top your overflow tank till it gets to the full level. And top your radiator till it gets to the brim.

Should my coolant overflow be empty?

No, if you notice that there is no coolant in the overflow tank, you don’t have to refill it. You have to inspect for coolant leaks with your underhood work light. Also, inspect the level of coolant in your radiator. Always ensure your radiator is filled to the brim. It is advisable to check your radiator every morning before starting your car.

Can I drive with an empty reservoir tank?

It is not advisable to drive with an empty reservoir tank. If your reservoir tank is empty, your radiator might be low as well since it sends and draws coolant from the reservoir. Ensure you inspect your water hose, radiator cap, and the radiator itself immediately if you notice an empty reservoir tank.

Final words

The level of coolant to pour into the reservoir tank is just as important as the color and type of coolant you intend to pour into the system. Always ensure you pour the right amount of coolant into your reservoir tank. I believe by now. You should be able to answer questions like how much coolant should be in the overflow tank and how the engine works.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

3 thoughts on “How Much Coolant Should Be In The Overflow Tank?

  1. What’s wrong when my overflow tank is over-filled but the radiator itself is low (exposed metal tubes) on a cold engine?

  2. Hello Rosalie,

    A coolant reservoir acts as a regulating component to the excess coolant that’s produced from the heat in your engine. As the warmth rises, coolant expands and overflows into the coolant reservoir and is then sucked back into the radiator as your car cools down after shut-off.

    If there’s no coolant in the reservoir, the excess coolant that enters the reservoir when warmth rises will remain there even when you shut off the engine. This will cause low coolant level.

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