The purpose of the cooling system is to keep the engine running at an optimal temperature to allow the engine to run efficiently.

The Basics

While most people think of the engine cooling system as the green fluid often called engine coolant or antifreeze coolant, the coolant is just a small part of the engine cooling system. The coolant acts as a medium as it passes through the cooling system. It starts in the radiator and is pumped by the water pump through hoses to the engine block and then back to the radiator. It takes the heat from the engine and transfers it to the fins on the radiator allowing the air to cool the fluid and the cooling system itself. The thermostat controls the cooling fan on the radiator determining when it needs to be on or off and also connects to the driver's control panel to indicate the coolant temperature.


The coolant system also has a branch that goes into the passenger cabin called the heating coil. This is where the car’s environmental controls draw heat from. In some cases turning on the heat can help to cool the engine.

Normal Wear

Traditional coolant has a life expectancy of 3 years or 36,000 miles because it is petroleum based and it starts to break down. Around 2005 a new coolant was developed based on a synthetic base to give it an extended life. Now coolant lasts up to 100,000 miles.

What Can Go Wrong

The material in the rubber hoses used in the coolant system can break down and fail without proper maintenance. This is mostly due to the coolant becoming corrosive and eating away at the rubber. Additionally, coolant that is not working as well as it should allows for much higher temperature ranges that cause the rubber to expand and contract more, advancing the breakdown process.
In newer vehicles, in order to reduce weight, a plastic tank is used for the radiator. Extreme temperatures can cause the plastic tank to crack and leak the coolant out of the system.

The water pump requires lubrication to work properly. Older coolant can lack the lubrication needed to keep the water pump working well and this may result in water pump failure.

Care and Maintenance

Most manufacturers highly recommend maintenance on the cooling system within the 60,000 to 70,000 mile window. During this time, the fluid can become corrosive and the lubricants become depleted. The combination can cause the parts of the cooling system to wear over time. On cars older than 2005, most manufacturers recommend maintenance every 36,000 miles to keep the system operating properly.

Proper care and maintenance includes getting the cooling system inspected and serviced every 3 years or 36,000 miles to prevent issues from arising. AAA reports that the number 4 reason for car breakdowns is a failure in a coolant system hose. Inspection and service can illuminate these issues before they cause a breakdown.