Radiator Coolant Overflow Tank: Functions, Bad symptoms and Replacement Cost

The purpose of the radiator coolant overflow tank is to prevent your vehicle’s cooling system from forming rust. As you may know, an engine that is working very hard will heat up very quickly. The oil alone is not enough to keep the components of the engine cooled off. The engine relies on coolant to ensure that it does not overheat during these high performing situations. While this heat is being generated, the coolant liquid will absorb it all so that the engine stays cool.

Basic Functions

Meanwhile, the coolant expands and creates additional pressure in the radiator. As the pressure causes the coolant to get higher than the pressure cap, the excess coolant needs to be captured somewhere in order to prevent leakage. So, the radiator coolant overflow tank functions to serve this exact purpose. The excess fluid flows into the overflow tube and goes into the overflow tank. Once the driver parks the vehicle and turns off the engine, the heat dissipates which causes the coolant to not be as hot anymore. The coolant will then contract instead of expand; resulting in the volume of the coolant decreasing. This is kind of like a vacuum effect where the pressure decrease allows the excess coolant in the overflow tank to flow back out of it, so it can return to the radiator.

The Top 5 Symptoms

Below are the top 5 symptoms of a bad radiator coolant overflow tank.

1) Rust Formation – Since the whole purpose of the radiator coolant overflow tank is to prevent rust from forming in the radiator, a faulty radiator coolant overflow tank will mean that rust will form in the radiator. If you see rust in the radiator, then you should immediately assume the overflow tank is having problems. You will need to have the tank replaced in this situation.

2) Coolant Leak – If the radiator coolant overflow tank is damaged or cracked, then you can expect coolant fluid to leak out of it. Sometimes cracks will form on the overflow tank if it is too old and worn out. You should notice puddles of coolant or streams of coolant because of these leaks.

3) Coolant Odor – In addition to the coolant leak, there will be an apparent coolant smell coming from the cooling system. If it gets bad enough then it may even circulate throughout the cabin of your vehicle. This is not a smell that you will want to get used to. Do something about the radiator coolant overflow tank right away.

4) Overheated Engine – Since the coolant’s job is to cool the engine when it is overworked, a leak will mean that your engine is not being cooled properly. As a result, you can expect the temperature of your engine to rise and become overheated. This will be indicated on the engine temperature gauge located on the dashboard.

5) Low Level of Coolant – If you check your coolant levels in the radiator coolant overflow tank and they are low, then you either have slowly evaporating or leaking coolant. Usually, people who don’t realize they have a leak may discover that it is a small leak which is barely noticeable on the outside. So, they need to check the coolant level for themselves to discover the leak is occurring.

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Replacement Cost

The cost to replace a radiator coolant overflow tank is anywhere from $90 to $260. The parts cost will be between $50 and $150 while the labor costs will be anywhere from $40 to $110. There will also be additional fees and taxes added to this as well.

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