Here's a general outline. This is NOT a complete, step-by-step guide, and variations may exist depending on your specific Alero's configuration. Consult a repair manual specific to your 1999 Oldsmobile Alero 3.4L for detailed instructions and diagrams. A Haynes or Chilton manual is a good investment for such tasks.
Tools You'll Likely Need:
* Socket wrench set (metric)
* Ratchet and extensions
* Pliers
* Drain pan
* New thermostat (the correct one for your engine - verify the part number!)
* New gasket (often included with the thermostat)
* Antifreeze/coolant
* Funnel
* Jack and jack stands (crucial for safety!)
General Steps (Consult your repair manual for precise details):
1. Cool Down: Let the engine cool completely. This is critical to avoid serious burns.
2. Vehicle Preparation: Jack up the front of the vehicle and securely support it with jack stands. Never work under a car supported only by a jack.
3. Drain Coolant: Locate the radiator drain petcock (usually at the bottom of the radiator) and carefully open it to drain the coolant into your drain pan.
4. Access the Thermostat: This is usually located at the bottom of the engine, near the water pump. You may need to remove some components (e.g., various hoses, possibly parts of the engine shroud) to gain access. This is where a repair manual's diagrams are invaluable.
5. Remove the Thermostat Housing: Carefully remove the bolts securing the thermostat housing. The housing may be somewhat difficult to remove. Take note of how everything is assembled.
6. Remove the Old Thermostat: The thermostat will be inside the housing. Carefully remove it. Inspect the housing and gasket for damage.
7. Install the New Thermostat and Gasket: Install the new gasket (if needed) and the new thermostat into the housing, ensuring it's seated correctly.
8. Reassemble: Carefully reassemble the thermostat housing, ensuring all bolts are tightened to the correct torque specification (check your repair manual).
9. Refill Coolant: Refill the radiator with the correct type and amount of coolant. Consult your owner's manual for the proper coolant type. You might need to add coolant through the overflow tank as well.
10. Bleed the System: After refilling, run the engine for a few minutes to allow the air to purge from the cooling system. This is very important to prevent overheating. Consult your repair manual for the correct bleeding procedure. Check for leaks.
11. Top Off: Once cooled, check the coolant level and add more if necessary.
Important Considerations:
* Repair Manual: A repair manual is crucial. This description is a general overview, and specific procedures may differ.
* Torque Specifications: Tighten all bolts to the correct torque specifications as recommended in your repair manual. Over-tightening can damage components.
* Coolant Type: Use the correct type of coolant specified in your owner's manual. Mixing different types can be detrimental.
* Safety: Always prioritize safety. Work in a well-ventilated area, and never work under a vehicle supported only by a jack.
If you're not comfortable performing this repair yourself, take your car to a qualified mechanic. Improperly installing a thermostat can lead to engine overheating and serious damage.
