How to Flush the Cooling System on a Northstar Engineby Russell Wood
If you don't properly maintain your vehicle's cooling system through yearly flushes, it will develop problems. Without annual flushing, the cooling system starts to corrode internal parts and can cause the head gasket to fail as early as 60,000 miles. The Cadillac Northstar engine is particularly prone to such issues. But preventing them is easy.
Wait for the vehicle to be completely cool before starting the flush. You should be able to place your flat palm onto the radiator cap without getting burned.
Place the bucket underneath the radiator, and open the draincock. It's a small, white knob on the bottom of the radiator, and it will completely drain all coolant in the radiator. Once it's drained, close the draincock.
Open the radiator cap and pour in the radiator flush. Then fill the rest of the radiator with water from a hose, and replace the radiator cap.
Run the engine for 20 minutes with the heater on high and on the hottest setting. It should take about 10 minutes for the car to reach operating temperature, then 10 minutes after that to circulate the flush.
Allow the engine to completely cool, then drain the radiator again in the bucket, using the same procedures.
Fill the radiator with water, close the radiator cap and allow it to run again, following the same procedure as in step 4.
Let the engine cool off, drain the radiator one last time and then fill it up with a 50/50 mixture of coolant and distilled water. Then close the radiator cap all the way.
Run the engine for 20 minutes to allow the coolant to mix with the water properly.