Where is the coolant block drain plug on 1999 Chevy s10 v6 4.3L?

On a 1999 Chevy S10 4.3L V6, the coolant drain plug is located on the lower passenger side of the engine block. It's usually a small bolt or plug near the bottom of the engine, somewhat towards the front. You'll likely need to get under the truck to access it properly.

Important Note: Because it's not always in the exact same spot across all 4.3L engines, a visual inspection is the best way to be sure. A repair manual specific to your year and model will be invaluable for accurate placement and for other important service steps involved in draining the coolant. A picture search online for "1999 Chevy S10 4.3L engine coolant drain plug" may also help you locate it visually.