Expansion Tank vs Overflow Tank

There are two types of coolant tanks in an engine compartment. One is Expansion tank & Another is Overflow Tank. Here, We have discussed the difference between them.

Expansion Tank –

Expansion Tank is generally mounted in front of the engine and connected to the radiator. When engine gets too hot, then coolant expands according to its nature and got pressurised. This pressurised coolant is stored in expansion tank.

Radiator cap is designed in such a way that it gets opened only by pressurised fluid. So when engine becomes hot & coolant gets pressurised then Cap becomes just an open gateway for coolant passing into expansion tank.

We can see a coolant level from Expansion tank. It has a translucent plastic material. Expansion tank’s hose is connected to radiator pressure cap. Never try to open this cap when engine is too hot. Always see coolant by opening this cap if you want but Be sure about engine’s temperature is cold.

So Expansion Tank is a reservoir for radiator’s pressurised coolant & It is helpful in terms of pressurised coolant’s storage. It avoids the danger of spreading out the coolant anywhere & damaging the system components internally & externally.

Overflow Tank –

Overflow tank is generally mounted at the backside of the engine or in front of the left side of the engine. It is also connected to the radiator by hose. It is an an unpressurized storage reservoir for engine coolant.

The main difference is pressure. There is no pressurised coolant’s flow into the overflow tank. Overflow tank has markings of hot & cold levels. You should have the basic knowledge about filling up a new coolant upto those markings.

We can see coolant’s level from overflow tank. It is also made up of translucent plastic material. Also we can determine / check the quality of coolant over the period of time by opening a cap.

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