The Purpose of Radiator Overflow Tank in Your Car

Last Updated on June 24, 2019 by themechanic

The internal combustion engine gets hot very easily. When it is running, there are several moving components in the engine which cause friction and generate heat. To keep the engine working normally, coolant must run through its components to absorb the heat they generate.

Basic Function and Working Principle

The coolant carries this heat into the radiator, causing it to expand. This means the coolant pressure increases in the radiator. If the pressure gets to be more than the pressure cap setting and seal can handle, then the coolant ends up in the radiator overflow tank.

So basically, the purpose of the radiator overflow tank is to prevent the coolant fluid from leaking out when the pressure increases in the radiator. There is something called an overflow tube which carries the flow of excess coolant into the radiator overflow tank. When you eventually park the car and turn it off, the temperature settles down and the coolant cools down. This means the coolant will contract more because it is under less pressure. As a result, there is a decrease in the volume of the existing coolant that is in the radiator. Once there is less volume, the excess coolant which sits in the overflow tank can now come back out and flow to the radiator.

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Prevent Rust

Aside from preventing a coolant leak, a radiator overflow tank allows coolant to enter the radiator instead of air. If you don’t have a radiator overflow tank in your car or if your tank has become faulty, then it can cause rust to form inside your radiator. This happens whenever air enters the radiator, so you don’t want this to occur.

Rust formation inside your radiator can cause it to malfunction. Without a functional radiator, cool coolant won’t circulate back to your engine to cool it off again. Then you’ll need to spend money on repairs or possibly even a replacement of the entire radiator if the condition has gotten bad enough. And if the engine overheats too much, you may have to spend even more money repairing or replacing that as well.

Be Aware of a Bad Overflow Tank

Most modern vehicles have a radiator coolant overflow tank. However, there is still a chance of them getting cracked or damaged. Anytime you are aware of coolant fluid leaking from your cooling system, you should inspect the overflow tank for signs of damage or wear. The leakage will be easily noticeable because you’ll see puddles or possibly even streams of the fluid on the ground. In addition, there may be a distinct coolant smell inside the cabin which comes from your vehicle’s cooling system. At this point, you should get your overflow tank replaced immediately. It is not healthy to keep smelling these fumes.

Since the engine is affected by a bad radiator coolant overflow tank, you should notice the Check Engine warning light illuminate on your dashboard whenever there is a problem with the tank. The needle of the tachometer will also show it toward the red zone, which means your engine is overheating. Therefore, you’ll have plenty of warnings and symptoms present themselves whenever it’s time to replace your overflow tank. Listen to these warning signs and take action right away.

Replacement Cost

A radiator coolant overflow tank does not cost that much money to replace. The total cost is likely going to be between $90 and $260. The cost of the parts will be around $50 to $150, while the cost of the labor will be between $40 and $110. But if you don’t do anything and let your radiator and engine become affected, you could be looking at thousands of dollars in repairs. So, it is a very cheap investment to replace your overflow tank.

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