1995 GMC Sonoma Owner's Manual - Page 201

1 5. Put the cap back on the coolant recovery tank, but leave the radiator pressure cap off. 6. Start the engine and let it run until you can feelthe upper radiator hose getting hot. Watch out forthe engine fan. 7. By this time the coolant level inside the radiator filler neck may be lower. If the level is lower, add more of the proper mix through the filler neck until the level reaches the base of the filler neck. 8. Then replace the pressure cap. At any time during this procedure if coolant begins to flow out of the filler neck, reinstall the pressure cap. Be sure the arrows on the pressure cap lineup like this.