Tools You'll Need:
* New Thermostat: Make sure you get the correct thermostat for your 350 engine. The temperature rating (usually 195°F) should be the same as the old one unless you have a specific reason to change it.
* New Thermostat Gasket: Essential to prevent leaks.
* Socket Set: Various sizes, likely including a 10mm, 13mm, and possibly others.
* Wrench Set: Similar to the socket set, you may need a few different sizes.
* Pliers: Needle-nose pliers can be helpful.
* Drain Pan: To catch coolant.
* Funnel: For refilling the coolant.
* Gloves: To protect your hands from coolant.
* Shop Rags or Paper Towels: For cleanup.
* Coolant: The correct type for your vehicle (check your owner's manual).
Procedure:
1. Safety First: Let the engine cool completely before starting this process. Coolant is hot and can cause serious burns.
2. Drain the Coolant: Locate the drain petcock at the bottom of the radiator. Place your drain pan underneath and carefully open the petcock to drain the coolant.
3. Locate the Thermostat Housing: The thermostat housing is usually located on the engine block, near the top of the engine, where the upper radiator hose connects. This area can be tight to access. Your repair manual will show you the exact location.
4. Disconnect the Upper Radiator Hose: Carefully disconnect the upper radiator hose from the thermostat housing. Have a rag handy to catch any remaining coolant.
5. Remove the Thermostat Housing: This often involves removing several bolts (usually 2-3) securing the housing to the engine block. Carefully remove the bolts and set them aside in a safe place. The housing may be somewhat stiff, so gently work it loose.
6. Remove the Old Thermostat: Once the housing is off, you'll see the old thermostat and gasket. Carefully remove the old thermostat. Inspect the gasket for damage; it should be replaced regardless.
7. Install the New Thermostat and Gasket: Install the new gasket into the thermostat housing, ensuring it's seated correctly. Then, carefully install the new thermostat. Make sure the thermostat is oriented correctly (usually there's a small notch or marking to indicate proper placement).
8. Reassemble the Thermostat Housing: Carefully reinstall the thermostat housing, making sure the gasket is properly seated and all bolts are tightened evenly.
9. Reconnect the Upper Radiator Hose: Reconnect the upper radiator hose to the thermostat housing.
10. Refill the Cooling System: Use a funnel to carefully add the correct type and amount of coolant to the radiator. Consult your owner's manual for the proper coolant type and capacity. You may need to add coolant to the overflow reservoir as well.
11. Bleed the Air from the System: Start the engine and let it run until it reaches operating temperature. Check for leaks around the thermostat housing. Monitor the coolant level in the radiator and overflow reservoir and add coolant as needed. You may need to open the radiator cap carefully (wait until the engine is cool) to release trapped air bubbles. Some vehicles have bleeder valves to help with this process.
12. Check for Leaks: After the engine has cooled down, carefully inspect the thermostat housing and surrounding areas for any coolant leaks.
Important Notes:
* Repair Manual: This is crucial! A repair manual specific to your 1990 G20 van with a 350 engine will provide detailed diagrams and instructions. This guide is only a general overview.
* Coolant Type: Use the correct type of coolant specified in your owner's manual. Mixing different types of coolant can be detrimental to your engine.
* Safety: Always prioritize safety. Work in a well-ventilated area and wear appropriate safety gear.
If you're not comfortable performing this repair yourself, it's best to take your van to a qualified mechanic. Improperly replacing the thermostat can lead to engine overheating and damage.
