How to Flush the Cooling System on a Northstar Engine

by Russell WoodUpdated July 06, 2023

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.

Things You'll Need:

  • Bucket
  • Radiator flush
  • Coolant
  • Distilled water
  • Hose and water source

1. Wait for the vehicle to be completely cool

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.

2. Place the bucket underneath the radiator

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.

3. Open the radiator cap and pour in the radiator flush

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.

4. Run the engine for 20 minutes with the heater on high

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.

5. Allow the engine to completely cool

Allow the engine to completely cool, then drain the radiator again in the bucket, using the same procedures.

6. Fill the radiator with water

Fill the radiator with water, close the radiator cap and allow it to run again, following the same procedure as in step 4.

7. Let the engine cool off

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.

8. Run the engine for 20 minutes

Run the engine for 20 minutes to allow the coolant to mix with the water properly.

Video showing a radiator replacement for a Northstar:

Comments on this video:

  • What a refreshing auto repair video! I'm dad raised 5 kids as a mechanic...first...I salute and join you in your "appreciation " of auto engineers"... I've made a point of owning pickups no newer than 1985...confident I could fix anything that went wrong. I started having kids who, as they "grew up" wanted cars that held current staus with their friends. I warned them if they bought vehicles that, when the hood was raised, looked like a drunk plumber built it I would be unavailable for repairs. Of course my first 4 kids are girls/women so I tried to keep up as much as possible but as my colorful language grew in creativity and volume I realized why my mom tried to keep us kids away from the shop area when my dad was working on a friend's vehicle on his weekends away from his job in a shop.for whatever brainfart reason I recently acquired a 98 de Ville... your video on the cooling system kept me from parking my "caddy" in the deepest canyon of "hell" . And your "calm " ironic personality kept my cooling system from driving me over "the edge ", whatever that I'm having a shot or two of Hornitos and diving in more relaxed and accepting of just another job. I'm subscribing and recommending your videos.. and there will be a 98 de Ville for sale soon.
  • I am no mechanic, but having this ride is turning me into a pro. thanks for the vid. Lifesaver.

More Articles

article divider