The thermostat on a 1999 Nissan Altima is located in the thermostat housing, which is attached to the engine block. It can be found on the front side of the engine, slightly to the right of the center.
Here's a general procedure for replacing the thermostat:
1. Gather Tools and Materials:
- New thermostat (OEM or equivalent)
- Replacement gasket (if needed)
- New coolant/antifreeze
- Socket set
- Flat-head screwdriver
- Pliers
2. Allow the Engine to Cool:
- Before starting, ensure that the engine is completely cool. This is important for safety, particularly if you need to drain coolant from the system.
3. Drain Coolant:
- Locate the drain plug at the bottom of the radiator. Place a suitable drain container underneath and use a flat-head screwdriver to remove the plug.
- Allow the coolant to drain.
4. Access the Thermostat Housing:
- Once most of the coolant has drained, find the thermostat housing. There might be a cover that you need to remove first to access it.
5. Remove the Thermostat Housing:
- There will be bolts or screws holding the thermostat housing in place. Use a socket or screwdriver to remove them.
- Be cautious as there might be some remaining coolant inside.
6. Remove the Old Thermostat:
- Once the housing is off, you'll see the thermostat installed in its place.
- Use pliers or your hands to gently remove it. Be careful not to damage the gasket.
7. Replace the Gasket (if needed):
- If the old gasket appears worn or damaged, replace it with a new one. Ensure that it properly fits and is seated correctly.
8. Install the New Thermostat:
- Take the new thermostat and place it in the thermostat housing. Ensure it's properly oriented and seated.
9. Reattach the Thermostat Housing:
- Reinstall the bolts or screws that secure the thermostat housing. Don't over-tighten them.
10. Refill the Cooling System:
- Check coolant level in reservoir and refill as needed.
- Open the bleeder screw on top of thermostat to purge air from the system, or consult the vehicle service manual to determine if the engine needs burped to properly bleed air from the system.
11. Start the Engine and Check:
- Start the vehicle to let it run for a few minutes. Keep an eye on the temperature gauge to confirm proper functioning.
12. Check for Leaks:
- Periodically inspect the area around the thermostat housing to ensure there is no coolant leakage.
Note: These steps are general and may vary based on the exact model and trim of the vehicle. It's always a good idea to consult your car's service manual for specific instructions. If you're not confident in performing these steps, it's best to seek assistance from a qualified mechanic.
