Replacing this thermostat requires significant disassembly:
1. Safety First: Disconnect the negative battery terminal before starting any work. Allow the engine to cool completely.
2. Coolant Drain: Drain the engine coolant. Locate the drain plug (usually at the bottom of the radiator) and a suitable container.
3. Access: To access the coolant housing with the thermostat, you'll likely need to remove various components depending on how much access you have. This *could* include:
* Upper radiator hose: Disconnect and remove this hose.
* Air intake components: Parts of the air intake system might need to be removed to get a clear view and access to the coolant housing.
* Other hoses and connections: Depending on the specifics of your car and how much room you have, additional hoses and electrical connections to the coolant housing might need disconnecting and moving.
* Possibly even the intake manifold: In some cases, depending on the exact year and model variations, access might necessitate removing parts of the intake manifold. This is a very involved procedure.
4. Coolant Housing Removal: Once you have sufficient access, remove the coolant housing itself. This usually involves several bolts.
5. Thermostat Replacement: The thermostat is now accessible within the housing. Carefully remove the old thermostat and replace it with a new one, ensuring a proper seal. Consult a repair manual for specific instructions related to the thermostat's orientation and gasket replacement.
6. Reassembly: Reassemble everything in reverse order, ensuring all hoses, connections, and bolts are properly tightened and seated.
7. Refill and Bleed: Refill the cooling system with the correct coolant mixture (check your owner's manual). Bleed the cooling system to remove any trapped air. This is crucial to prevent overheating.
Crucial Considerations:
* Repair Manual: A service manual specific to your 1996 Cadillac DeVille with the Northstar engine is highly recommended. This will provide detailed diagrams, torque specifications, and step-by-step instructions. Haynes and Chilton are common brands.
* Mechanical Aptitude: This is not a beginner-level repair. If you're not comfortable with automotive repair, it's best to take it to a qualified mechanic. Incorrect reassembly can lead to serious engine damage.
* Special Tools: You may need specialized tools, such as sockets, wrenches, and possibly a coolant bleeding tool.
In short, replacing the thermostat on a Northstar engine is significantly more complex than on most engines. Don't attempt it unless you have experience with automotive repair and access to the correct tools and a service manual. The potential cost of damaging the engine far outweighs the cost of professional service.
