refill cooling system, use the little brass bleeder screw on top of the motor to bleed out the air until a steady stream of coolant is coming out after the engine is warmed up. place gasket over the thermostat (you can put a thin bead of RTV sealant on both sides of the gasket if you wish, some people think it's overkill, but i hate doing things twice) 7. place new t-stat on engine side opening 6. scrape any gasket material off mating surface on engine side, being even more careful not to gouge the metal here 5. pull thermostat out of engine block (it's easy to see w/ the water neck off) 4. unbolt and remove the water neck from the engine block (it's attached to the upper radiator hose) and scrape any leftover gasket material off of the mating surface w/ a razor or gasket scraper, being careful not to actually gouge the metal 3. 2000 chev has a low coolant light on inside the dash and the. It has advanced synthetic technology that resists chemical breakdown for maximum wear protection for your vehicle which is well beyond the traditional 3,000-mile oil change interval. The second tank that is smaller (called the 'low read more. AMSOIL OE Synthetic Motor Oil is specially made for the extended oil change intervals recommended for your 1999 Chevrolet Lumina 3.1L. SOURCE: replacing thermostat on 3100 sfi v6ġ. The low coolant light came on on my 2020 Duramax L5P but when I checked the level, it was actually above the fill mark on the main coolant surge tank.