Coolant Overflow Tanks

The engine cooling system is very complex and includes several subsystems. One of them is the coolant recovery system, which ensures that there is no air in the system, and prevents coolant from spilling onto the ground. Since air causes cooling system components to rust and corrode, its presence in the system can lead to leaks of the antifreeze, which contains ethylene glycol that is harmful to the environment. As coolant circulates through the cooling system, it picks up metal particles, which also contributes to its classification as hazardous material.

In the coolant recovery system, coolant is added to a separate plastic tank that is connected to the radiator. There are usually graduations molded into the reservoir indicating the proper coolant level, which is customarily checked when the engine is cold. However, not all systems are the same. There are overflow tank systems and expansion tank systems. In an overflow system, the pressure cap is located on the radiator and the overflow tank has a simple plastic cap. When pressure in the radiator exceeds the cap’s pressure rating, coolant is allowed to flow from the radiator to the recovery tank. When the temperature of the coolant drops, a vacuum is created in the system, opening a vacuum valve in the pressure cap which allows coolant to be drawn back into the radiator.

The pressure cap is located on the tank in the expansion tank system. Because the tank is part of the pressurized cooling system, it is made of heavier reinforced plastic. In this system the expansion tank is the highest point in the cooling system, and room is built into the tank to allow for the coolant to expand and contract according to temperature. The pressure cap functions the same as in the overflow system, but instead of coolant, air is released when pressure exceeds the cap’s pressure rating, and atmospheric pressure forces air back in when the coolant temperature drops and there is a vacuum in the system. Air does not present a problem for the system here because the tank is above the radiator and in this position will not aerate the coolant.

We recommend you to inspect the coolant recovery tank for cracks and any signs of leakage on a regular basis. Although, the components are generally reliable but they can deteriorate from age and repeated heat cycling. They can also become discolored from contaminated coolant, making it hard to judge the coolant level accurately. If you need a quality replacement, you are in the right place. We also offer lots of performance units. By itself, one of our performance coolant tanks will be a practical and stylish addition to your cooling system, but it’s also the perfect complement to a performance radiator, cooling fan and other cooling system and underhood modifications. We offer both universal and direct fit coolant tanks, manufactured from strong and durable aluminum or stainless steel. And while most have an attractive bright natural finish, some are available polished, chrome plated, or in anodized or powder coated colors.

We offer performance coolant tanks for both expansion tank and overflow tank applications, and some can be used for either system type. Many of our expansion tanks have greater capacity, so you can increase the overall coolant capacity of your system. Our universal tanks come in a wide range of shapes and sizes, so you can get the tank that’s the right fit for your vehicle, and most come with universal mounting brackets and hardware to facilitate installation. We have direct fit tanks for most popular vehicle applications. These tanks are designed to bolt on in the same location as the original plastic tank, and some feature an external sight gauge to allow a quick check of coolant level.