Radium Engineering Coolant Expansion Tank – Universal




Instructions & Videos

Coolant expansion tanks are necessary for proper air bleeding in applications that utilize a low mounted radiator (such as a V-Mount) or rear-mounted radiator. However, expansion tanks are also valuable if integrated into a common radiator setup. To allow heat expansion, traditional coolant systems require air to be present in the top portion of the radiator during low temperatures. A coolant expansion tank permits the radiator to be 100% filled with coolant in all conditions.

The Radium Coolant Expansion Tank holds 750mL. It is a 2-piece design constructed of CNC billet 6061 aluminum. The two halves (shown below) are bolted together along with a CNC billet aluminum radiator neck which accepts a standard 32mm “Mini” style pressure cap. The radiator cap must have a Type-A seal as shown HERE.

2x Bottom ports: -10AN ORB
1x Front port: -6AN ORB

The coolant expansion tank features two internal chambers. These chambers are NOT isolated from each other. There are cross-over passages at the top and bottom. This product is not a coolant overflow tank. Instead, it is designed to part of the pressurized coolant system.

The Radium Engineering coolant header tank also has an internal swirl feature, as shown below. Hot pressurized coolant from the cylinder head is sent into the vortex chamber’s inlet tangentially and accelerated to a high rate of rotation. This is to help aid in deaerating the system.

The tank features three O-ring boss ports for a positive seal. Included are -6AN male adapter fittings (not tapered pipe threads). The lower ports are machined with 10AN ORB threads. For a list of other 10AN ORB and 6AN ORB adapter fittings that can be used, please check our website. The side port is machined with 6AN ORB threads. Included are three -6AN female 90-degree hose ends that screw onto the three -6AN male port fittings. They are lightweight black anodized aluminum and are used for push-lok style 3/8″ ID hose.


-Billet Aluminum Coolant Tank
-Anodized Aluminum Mounting Bracket
-6AN Male Adapter Fittings (x3)
-6AN 90 degree Push-Lok Hose Ends (x3)
-Nickel-Plated Fittings and Sight Tube
-Billet Aluminum 32mm Pressure Cap Receiver
-Aluminum Pressure Bleed 1/4″ Barb
-Stainless Steel Hardware


A black powder-coated laser-cut mounting bracket is included.

See the dimension drawing below.

Pressure Caps

The optional Radium Engineering pressure caps (sold separately) allow the user to select a range of pressure. The purpose of a high-pressure cap is to increase the boiling point in the cooling system providing improved cooling efficiency. Each cap is manufactured from stainless steel with a race-proven high-pressure valve. This is something to consider when tracking the vehicle in extreme conditions. For more information and to purchase, go HERE.

Radium Pressure Cap – 1.1 Bar (110 kPA, 15.6 psi)
Radium Pressure Cap – 1.3 Bar (130 kPA, 18.9 psi)
Radium Pressure Cap – 1.5 Bar (150 kPA, 21.8 psi)

Additional information

Weight2 kg
Dimensions30 × 20 × 20 cm


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