What is a fuel cooler and where is it located?

Fuel coolers cool the temperature of a vehicle’s fuel. They are typically found on diesel trucks, and usually cool the gas traveling in the fuel return lines. As emission laws have changed, automakers have developed new technology to meet its standards. One of these technologies is high pressure fuel injection, which in turn heats up the fuel to be recycled. Hotter fuel can put a strain on plastic fuel tanks, the fuel pump and its circuitry, and the engine’s performance. Hotter fuel also means less density, and less density means less mass to be burned, which can alter the fuel:air ratio and lead to poor combustion.

Fuel coolers help solve this problem. They generally connect to the return fuel lines and a line of its own mix of 50/50 coolant and water. It works in similar fashion to a radiator. A pump will send coolant through the system, which will travel through the fuel cooler alongside the hot fuel, absorbing the heat and thus cooling the fuel. Fuel coolers can also be air-cooled. You can find them in different places, such as in front of the fuel tank or on the return side of the fuel rail.

How do I know my fuel cooler needs to be replaced?

If your fuel cooler is leaking when the vehicle is parked, or if your running temperature is abnormally high, your fuel cooler might need to be replaced. Other symptoms can include rough starting and idling, a dip in RPM, or a loss in performance or horsepower. Abnormally low fuel coolant levels can be another sign.

Can I replace the fuel cooler myself?

Although some fuel coolers are DIY-friendly, we generally recommended leaving it to the professionals. But a typical repair might include depressurizing the fuel system, possibly draining the fuel cooling system, disconnecting the fuel and coolant lines to the cooler, and unbolting the mounting bolts from the cooler. There may be additional steps.