How do coolant recovery tanks work

This was good for radiators, and much better for our environment. Different manufacturers called them different things: overflow — to catch the overflow from the radiator; reservoir — to store the captured coolant; or recovery tank — to recover coolant that was expelled when the pressure increased.

The heavy spring on the radiator cap that can be seen is compressed when pressures reach roughly. The process of returning coolant back to the radiator is possible because the combination of the reduced steam pressure allows the atmospheric pressure to push coolant from the tank back into the radiator through the vented radiator cap. This, in turn, adds more coolant to your system and helps to keep the engine a little cooler.

Expelled coolant will enter the tank from the bottom, and when the level rises it will expel through the vent tube. The longest one on the outside is also the longest one on the inside. These tanks can be cylindrical, with both hoses attached at the bottom, like ours, or the factory style will enter at the bottom and the vent will be at the top.

The radiator had a filler neck at the top, usually to one side or the other rather than in the center, fitted with a filler cap. The system was filled -- properly referred to as charging -- through the filler neck after the cap had been removed. Most manufacturers recommended coolant be topped off at approximately 1 inch below the bottom of the filler neck; this allowed for expansion when the coolant was heated by the running engine.

The only way for the engine to vent excess pressure was through the filler cap. Different caps had different pounds-per-square-inch capacities that they could resist; when the limit was exceeded, steam was vented through an overflow vent beneath the cap to protect the engine. When, in the s, environmental awareness began to affect vehicle design and driver attitude, overflow bottles were added to the system to trap vented fluid as it was ejected.

The worst case would be an internal coolant leak caused by a bad had gasket or a cracked cylinder head or engine block. If damaged, the tank must be replaced. Replacement tanks can be purchased at most auto parts stores or car dealers. Also, use the SAME type of coolant that is already in the system, or a "universal" coolant that is fully compatible with the coolant in the system.

Changing the coolant on some late model vehicles can be a challenge because air may become trapped inside the engine, heater or hoses. To vent the trapped air, one or more "air bleed valves" may be located at various points in the cooling system. Opening the valve s when the system is being refilled allows air to escape so coolant can completely fill all the voids.

If the trapped air is not removed, it may block the flow of coolant through the heater core resulting in no heat output from the heater. Trapped air may also cause the engine to overheat when the vehicle is driven.

If there are no air-bleed valves, you may have to temporarily loosen a heater hose to vent air. Another trick is to use a jack to raise the front of the vehicle so the radiator is higher than the heater core. However, most modern cars require liquid cooled systems. A liquid cooled system typically features a radiator, fan, thermostat, water pump, a coolant tank, and a fill point. The type of coolant tank and the fill point location can vary depending on the system. In many modern cars the radiator is mounted lower than the engine.

Since the radiator is lower than the engine a pressure relief and fill point that is higher than the engine is needed. This is accomplished with an expansion tank. When the radiator is high enough to act as a fill point and pressure relief an expansion tank is not necessarily required.

In those applications a recovery style tank may be used instead. Liquid cooled systems are pressurized in order to raise the boiling point of the coolant.