*Tools and Materials Needed:*
- New Thermostat (OEM or high-quality replacement)
- 5/8 inch socket and ratchet
- Flat-head screwdriver
- Pliers
- Gasket scraper or razor blade
- Safety glasses
- Gloves
- Coolant (Mopar OAT coolant or equivalent)
- Funnel
- Rags or towels
- Bucket or pan for draining coolant
Procedure:*
1. Preparations:
- Park your truck on level ground and allow the engine to cool down completely.
- Engage the parking brake and ensure the truck is in the "Park" position if it's an automatic transmission.
2. Locate the Thermostat:
- Open the hood of your truck.
- The thermostat housing is located on the front side of the engine, towards the top. It's usually a round or oval-shaped housing with a single bolt on top.
3. Drain Coolant:
- Place a bucket or pan under the radiator.
- Locate the radiator drain petcock, usually a small valve near the bottom of the radiator.
- Turn the petcock counterclockwise to open it and allow the coolant to drain.
4. Remove the Thermostat Housing:
- Once most of the coolant has drained, use a 5/8 inch socket and ratchet to loosen and remove the single bolt on top of the thermostat housing.
- Be careful as there may still be some coolant in the housing.
- Lift the thermostat housing off carefully to avoid spilling coolant.
5. Remove the Old Thermostat:
- Inside the thermostat housing, you'll see the old thermostat. It's a round, disk-shaped component with a spring-loaded valve.
- Use a flat-head screwdriver or pliers to carefully pry the old thermostat out of its seat.
- Be sure to remove any old gasket material from the mating surfaces.
6. Install the New Thermostat:
- Inspect the new thermostat to ensure it's facing the correct direction. The valve should be facing towards the engine.
- Place the new thermostat into its seat and press it down gently until it's fully seated.
- Make sure the gasket is properly aligned and in place.
7. Reinstall the Thermostat Housing:
- Carefully place the thermostat housing back into position.
- Replace the bolt and tighten it securely using a 5/8 inch socket and ratchet.
8. Refill Coolant:
- Using a funnel, slowly pour the recommended amount of Mopar OAT coolant or an equivalent into the radiator.
- Fill until the coolant level reaches between the "Full" and "Add" marks on the radiator's overflow reservoir.
- Replace the radiator cap securely.
9. Test the System:
- Start the engine and let it run for a few minutes.
- Check for leaks around the thermostat housing and the radiator.
- Turn on the heater to the maximum setting and ensure hot air is coming through the vents.
10. Test Drive and Monitor Temperature:
- Take the truck for a short test drive, preferably on a highway or road where you can maintain a steady speed.
- Keep an eye on the temperature gauge to ensure it stays within the normal operating range.
11. Check Coolant Level:
- After the test drive, let the engine cool down and then check the coolant level again.
- If it's low, add more coolant until it reaches the proper level.
12. Clean Up:
- Clean any spilled coolant using a rag or towel.
- Dispose of the old coolant properly, following local regulations.
By following these steps, you can successfully replace the thermostat in your 1999 Dodge 1500 5.9L. Remember to take safety precautions and follow the instructions carefully. If you're unsure about any steps or encounter difficulties, it's best to seek assistance from a qualified mechanic or consult your vehicle's service manual.
