The coolant or chemical solution that absorbs heat from the engine of your Volvo is a compound mixture that expands after being heated. Normally, that reaction would also make the chemical to expand. If there's no port where the overflowing coolant would go, the tendency is for the expanded coolant to just be spilled, the Volvo engine would then need constant refill in order to keep the temperature in the desired level. How is it then being kept? A Volvo coolant tank is the solution. The moment it is heated, the overflow tube which is connected to the bottom of the coolant tank would direct the overflow to the container.
The importance of the Volvo tank is relies on the value of the coolant to the system, which ultimately is to prevent overheating. This is the device in a Volvo liquid cooling system that houses the coolant after it's been heated, right before it's directed to the radiator. With its capacity to hold an amount of coolant helps regulate the temperature in the engine system. And to ensure that there's enough or extra space for the expanded coolant, Volvos can be retrofitted with Volvo coolant expansion or fill tanks.
In earlier vehicle eras, air cooled systems are the ones being used. Unlike liquid cooling systems of today which make use of coolants, this type doesn't need coolant tanks. An air cooled system is simply being driven by a powerful fan that blows cold air over a heat conductor or aluminum fins that cover the engine block, which then absorb the heat from the cylinders. Basically, the cold air blown over the heat absorber transfers the heat to the atmosphere. On the other hand, liquid cooling systems use a liquid component which we call coolant to absorb heat produced in the engine operation. This liquid component is a mixture of water and anti-freeze usually of ethylene glycol and anti-corrosion chemicals. Significantly, the latter type of cooling system works more efficiently than the other.
As for Volvo that's known for producing heavy duty trucks and reliable cars, only high quality coolant tanks should be used so to complement the quality of engineering and sophistication. Superior quality aftermarket Volvo coolant tanks and coolant expansion tanks are available in the market, in case your original tank or expansion tank has gone out of good condition.