Help for 92 G20 Alternator and coolant drain

[WatsonJX]

I've got to replace the dead alternator...
However I can't reach it because it is hidden beneath
a coolant pipe. I have to drain some coolant and
remove the pipe before I can reach the alternator.

However I have no idea where the drain plug is.
Anybody can give em a hand ? What repair manual
should I have ? I have the service manual but it
doesn't have instruction on how to drain the coolant.

Thanks so much...

Xiong