Coolant Recovery System

The primary purpose of the coolant recovery system is to hold excess coolant when the engine hot and to provide a means for the excess to be returned to the radiator as the system cools. When the coolant temperature decreases, a partial vacuum is formed. This partial vacuum draws coolant back into the system through the vacuum valve until the system is full. If the vacuum valve does not function properly, this can cause coolant hoses to collapse. Typically, the upper radiator hose is the first one to be affected.

There are two different coolant recovery systems: pressurized recovery systems, and non-pressurized recovery systems.

Pressurized recovery systems are referred to as surge tanks and are easily recognized by their pressurized radiator caps. Surge tanks are located at the highest level in the coolant system and will have one hose going from the bottom of the tank and attached to the inlet side of the water pump. Another hose that is smaller in diameter attaches the side of the tank to the highest point of the radiator. This hose is referred to as a bleed hose and it allows coolant to circulate through the surge tank. It lets air rise up to the surge tank cap, where it can be forced from the system if the pressure goes up.

Non-pressurized recovery systems do not have a hose going to the water pump. They only have a bleed hose attached to the highest point of the radiator. They do not have a pressurized cap and you will not find any pressure rating on the cap, but there will be a pressurized cap directly connected to the radiator.

BEFORE REMOVING ANY PRESSURE CAP, WHETHER IT IS LOCATED ON THE RADIATOR OR THE RECOVERY SYSTEM, THE ENGINE MUST BE COOL. REMOVING THE CAP WHEN THE COOLANT IS HOT COULD RESULT IN SERIOUS INJURY AND BURNS.

There will always be a fill line half way up the side of the reservoir tank and it is important that the fluid be filled up to, but not above that line. The air space is required for the excess coolant when the engine is hot and fluid expands. It may be possible to see the fluid level through the tank, but often times it may be difficult to see because the tank may be stained from prolonged coolant exposure. In this case, tapping lightly on the side of the tank with your hand may make it possible for you to distinguish the current level or you may have to just remove the cap and glance inside the tank.

On pressurized recovery systems, when the reservoir tank is properly filled, that indicates that the entire coolant system is also properly filled. On non-pressurized systems, one cannot assume that the recovery system will always draw the proper amount of coolant back into the main coolant system. This makes it necessary to check the radiator directly on non-pressurized systems to ensure the fluid level is actually to the top of the radiator neck.

Refer to the coolant inspection and diagnostic page of our website before attempting any repairs to the coolant recovery system. The following step-by-step instructions will guide you through the removal and installation of both pressurized surge tanks and non-pressurized recovery tanks.