16 mm
The 1991 Pontiac Grand Am radiator drain plug can be found on the bottom of the radiator. The radiator drain plug will be in the center of the radiator bottom.
on the radiator
for what motor? a 3.8 L would be 0.060
On the oil pan.
Most vehicles do not.
It is on the bottom of the radiator on the drivers side.
Right under the battery
There is no drain plug assuming it is an automatic transmission it is drained when removing the transmission pan and changing the transmission filter.
Should be at the bottom of the radiator logically...
If it does not have a drain plug, just simply remove the lower radiator hose.
there may not be one if there is it is on the bottom if not you just remove the bottom radiator hose to drain
drivers side bottom of radiator.