It is located at the bottom of the radiator .
It's located on the lower driver side very corner of the radiator. It's a plastic nut with a couple tabs sticking out. Use a 19mm deep socket and short extension to unscrew it. The plug will come all the way out with a pull. It has a rubber seal on it so there will be a bit of resistance. Put it back just snug. You don't want to strip it. The rubber seal does the job, so it doesn't have to be real tight.
It is a small rubber plug on the bottom passenger side of radiator, just below the lower hose.
You likely need to replace your radiator cap - the rubber seal in the cap is worn.
my 2001 is at the middle bottom of radiator cover by rubber that are holding by 4 or 5 plastic pins
The rubber plug just covers the weep hole to hide any minor leakage from the water pump seal.The rubber plug just covers the weep hole to hide any minor leakage from the water pump seal.
Failed gasket, seal, hose, freeze plug, radiator.......
Rubber.
Got a leak somewhere alos check that your radiator cap rubber/seal is not worn out, fluids can be lost from their too.
(2003 Frontier) From beneath the truck, pull back the leading edge of the rubber splash guard that is below the radiator (it is held in with push pins and 1 Phillips screw). Once this is pulled back you can see the bottom of the radiator. In the center there is a plastic plug with a Phillips head. This is the drain plug. Unscrew it with a screwdriver and the radiator will start to drain.
Some do, some don't. Some even have a metal gasket. Just depends on the vehicle you are driving.
Most of the time they look like a small rubber o-ring or doughnut.