Safety First!
* Wear safety glasses and gloves: Coolant is corrosive.
* Work in a well-ventilated area: Coolant fumes are toxic.
* Let the engine cool completely: Hot coolant will scald you. Wait several hours after driving.
Tools and Materials:
* New coolant: Use the correct type specified in your owner's manual (usually a 50/50 mix of coolant and distilled water). The proper mix is crucial to prevent corrosion and freezing.
* Drain pan: Large enough to hold several gallons of coolant.
* Wrench(es): You'll need various sizes depending on your specific vehicle. Check your owner's manual for specifics, but expect to need wrenches for the drain plug(s) and possibly for the radiator cap.
* Funnel: To avoid spills when refilling.
* Hose clamps (optional): If you plan on replacing any coolant hoses.
* New radiator cap (recommended): These wear out over time and can cause pressure issues.
* Clean rags or shop towels: For cleaning up spills.
* Flashlight: To help see into tight spaces.
Procedure:
1. Locate Drain Plugs: The Northstar engine typically has a drain plug at the bottom of the radiator and a drain plug on the engine block. Consult your repair manual for the exact locations.
2. Drain the Radiator: Place your drain pan under the radiator drain plug. Carefully open the drain plug and let the coolant drain completely. This can take a while.
3. Drain the Engine Block: Once the radiator is drained, move the drain pan to position it under the engine block drain plug. Open this plug and drain the coolant from the engine block.
4. Remove Radiator Cap (optional but recommended): Once the majority of the coolant has drained, you can carefully remove the radiator cap to allow for complete drainage.
5. Reinstall Drain Plugs: Once drained, carefully replace and tighten both the radiator and engine block drain plugs.
6. Refill the Radiator: Using a funnel, carefully pour the pre-mixed coolant into the radiator until it's nearly full. Don't overfill, leave some room for expansion.
7. Bleed the Air from the System: This is crucial for proper cooling. The Northstar engine is known to trap air. There are a couple of ways to do this:
* Run the Engine: Start the engine and let it idle. Monitor the coolant level in the radiator. Add more coolant as needed, keeping an eye on the overflow tank. Run the engine until the thermostat opens (usually around 195-205°F). This can take a few minutes. Allow it to run for an additional 10-15 minutes to ensure proper circulation. Turn off the engine.
* Pressure Bleed (Preferred): If you have access to a coolant pressure tester, this is the best method to ensure complete air removal. This tool forces coolant throughout the system, eliminating air pockets efficiently.
8. Check Coolant Level and Add More as Needed: Once the engine has cooled, check the coolant level in the overflow tank and add coolant to the "cold" fill line.
9. Check for Leaks: Inspect the drain plugs, hoses, and connections for any leaks.
10. Run the Engine Again and Check for Leaks and Temperature: Run the engine again to ensure the temperature gauge reaches the normal operating range. Check for leaks again, especially after the engine has warmed up and the coolant has circulated.
Important Considerations:
* Repair Manual: A factory service manual or a Chilton/Haynes repair manual specific to your 1997 Cadillac DeVille is highly recommended. These manuals provide detailed diagrams and instructions, which are crucial for working on a car of this complexity.
* Coolant Type: Use the correct type of coolant as specified by Cadillac. Using the wrong coolant can damage the engine.
* Overflow Tank: Watch the overflow tank during the bleeding process. Coolant will likely expand and rise up.
This is a general guide. Always consult your owner's manual and consider seeking professional help if you're uncomfortable performing this task yourself. Incorrectly bleeding the cooling system can lead to overheating and engine damage.
