92 astro van

At the bottom of the radiator is the drain. It looks like a wing nut. Turn it counter clockwise to loosten and drain. NOTE: Make sure the engine is cold when you do this.

Hi J&N, got that much from the books (GM & Haynes) but no explanation of virtually impossible access. Drain petcock is below the lower radiator hose AND a cooling line (transm). The clearance from the side has but an inch between the radiator sidewall and chassis. From beneath there is no access because of steering linkage, sway bar, and cross beam support frame, and the lower fan shroud.
I determined that from above is best, after removing the cooling overflow tank. A LONG needlenose pliers might reach the petcock valve, so I invented a tool approach: modify an old 3/8 inch socket with a cross cut to fit over the valve; then use a foot long extension on a stubby wratchet wrench; your finger tips on the chassis side locates the socket, and the right hand operates the wrench. Hopefully you are skinny enough with long arms, to access the tool approach. It still is a mess with coolant dripping all over the cross frame and steering linkages.... the valve drain can use a 3/8 in. hose but even that is hard to access from the below front side between chassis and bumper.
Please let me know what you think.