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How to Refill a Northstar Cooling System

by Cassandra Tribe

The Cadillac division of GM made use of the Northstar engine in several of their models. Northstar engines are aluminum, split-case engines designed with a special air-cooling feature. When servicing the vehicle, it is extremely important to understand that the process to refill a Northstar cooling system is different from that on most other vehicles. Due to the uniqueness of the design, coolant supplement pellets must be added during the process. These pellets act as a kind of internal sealant to prevent leakage that can occur from the hot temperature that cab be achieved by the aluminum engine.

Step 1

Make sure that the drain cock on the bottom (driver's side) of the radiator is in the closed position and all hoses are attached.

Step 2

Remove the fill cap from the radiator and insert a funnel in the opening.

Step 3

Fill the radiator halfway with GM Goodwrench DEX-COOL coolant. This is the manufacturer's recommended coolant; while other coolants can be used, they may increase the risk of overheating and damage to the Northstar engine.

Step 4

Drop three pellets of GM coolant supplement (sealant) P/N 3634621 into the radiator. Do not crush the pellets -- they will dissolve on their own and pass through the system.

Step 5

Fill the radiator to the top with GM Goodwrench DEX-COOL coolant. Replace the radiator fill cap.

Step 6

Start the engine and let it warm to operating temperature. Shut the engine off.

Remove the radiator fill cap (the coolant will not be hot enough to be dangerous) and check the fluid level. Add more fluid if necessary, replace the cap and close the engine hood.

Tip

  • Northstar engines are made of aluminum and thus are prone to overheating. Investigate any "check engine" light immediately to avoid damage to the engine.

Warning

  • Any substitution for the supplement must be specifically rated to match the coolant, or it could create significant internal engine damage. It is preferable to use the manufacturer's recommended supplement rather than a different brand.

Items you will need

  • Funnel
  • GM Goodwrench DEX-COOL coolant
  • GM coolant supplement (sealant) P/N 3634621

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