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Radium Coolant Expansion Tank

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Product Description

The Radium Coolant Expansion Swirl Tank features three ports that use -6AN to 9/16-18 O-ring adapters (not tapered pipe threads) for a positive seal. The main tank is a 2-piece design constructed of cast aluminum. The two halves (shown below) are welded together along with a CNC billet aluminum cap receiver which mates to any standard 32mm “import” style pressure cap.

Coolant expansion tanks are necessary for proper air bleeding in applications that utilize a low mounted radiator, such as a V-Mount or a Rear-Mount, such as Michael Essa’s championship winning BMW E46 shown below.

The Radium Engineering 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 an old hot rod trick to help aid in deaerating the system.

Included are three -6AN female 90 degree hose ends that screw onto the three -6AN male coolant tank port fittings. They are lightweight black anodized aluminum and are used for push-lok style 3/8” ID hose.

All coolant tanks are pressure tested in house (shown below) and then powder coated texture black and laser etched.


  • Cast Aluminum Coolant Tank
  • Powder Coated Wrinkle Black
  • -6AN O-Ring Adapter Fittings
  • -6AN 90 degree Push-Lok Hose Ends
  • Nickel Plated Sight Tube Fittings
  • Billet Aluminum 32mm Pressure Cap Receiver
  • Billet Aluminum Pressure Bleed 1/4” Nipple

A laser cut black powercoated laser cut mounting bracket is included.

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