How Does a Radiator Coolant Overflow Tank Works?


Certain car components work by themselves while others coordinate with others to work smoothly. The radiator coolant is one of them that works in unison with other components to operate in a hassle-free manner. Let’s understand how the radiator coolant overflow tank works and common issues that might occur as it starts overflowing:

How Does a Radiator Coolant Overflow Tank Works?

The radiator coolant overflow tank working is not at all complicated and follows the proper process. The radiator coolant overflow is filled with coolant as the pressure becomes high and is eradicated when it gets low. Depending on the pressure, the coolant is added or taken out from the system. A cooling system works properly only when it has been sealed tightly. Thus, these leaks keep the coolant safe from dirt and debris along leaks. The design runs most of the time smoothly, but the real issue occurs when the system becomes hot. There are hardly any chances of expansion within the sealed system while boiling occurs as the system becomes over pressurized and dissipates from the weaker regions present in the system. This is when the overflow in the tank takes place. It is impossible for the coolant to stay within the system and start overflowing. As the coolant starts cooling, contraction occurs, and extra space is formed inside the cooling system. Coolant contraction leads to negative pressure, and extra coolant present in the coolant tank starts moving towards the main cooling system.


Coolant is a composition of water along with an anti-freeze mixture. Water is an excellent element added to the coolant and can be used in case of an emergency. The water qualities can be enhanced using an anti-freeze. The main goal of the coolant is to prevent water from freezing and surges its boiling temperature by several degrees. The car coolant consists of a rust protection formula generally applied to the internals that undergoes rusting due to water.

Water Pump

The system receives heat from the engine that needs to be taken out; then, the coolant movement from one section to another takes place with the help of a water pump. These water pumps generally function using an auxiliary driving belt or cambelt. The pulley comes with a propeller on the back and helps the coolant move around the engine and radiator pipes. The coolant system is completely sealed, so the water pump doesn’t have to make much effort while circulating the coolant.

Basically, your water pump is the primary component that abstains the coolant from overheating. The hot air received from the engine is sent to the radiator present at the engine’s front, and the fans or incoming air tries to cool it down. The cool liquid is re-circulated around the engine, and the process continues as long as the engine movement occurs.

If the water pump stops working for any reason, it leads to coolant overheating and starts pressurizing and boiling. This is a situation of coolant overheating, and the hot coolant is eliminated, leaving the system with less coolant.

Radiator Cap

The radiator cap is also one of the essential components of the cooling system. This works in amalgamation with the radiator overflow tank. It is a regular cap on the lid to most people, but in reality, it does more than that. The radiator valve comes with a spring-loaded valve as the temperature within the coolant surges, the pressure within leads to coolant expansion and excess coolant moving towards the overflow tank. This valve helps the system stay pressurized and prevents it from rising or dropping beyond a certain level.

What to Do When the Radiator Coolant Overflow Tank Leaks?

What to Do When the Radiator Coolant Overflow Tank Leaks?

In case there is a leakage in the coolant overflow tank, consulting a qualified mechanic would be the best course of action. However, if you possess sound technical knowledge, you can fix the leak via coolant overflow tank replacement and help the vehicle stay cool.

Where to Obtain Coolant Overflow Tank at Affordable Price?

You can get a coolant overflow tank from a car parts and accessories store onlineThe Auto Parts Shop’ that brings premium quality and genuine coolant from the store at reasonable rates. Watch the DIY videos so that the coolant installation is carried out in the right way.

The Bottom Line

This is how the overflow tank functions in alliance with other components. The coolant overflow system is an excellent piece and is designed in such a way that it works efficiently and effectively.

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