There are actually two "official" drains - one on the radiator (usually on the pax side, and I think you have to remove the grille to get at it) and a small plug with a 5/16" or 8m/m square drive recess. A key for this plug can be easily made from a 5/16" or an 8m/m hex key and five minutes' work with a grinder.
If you pull the lower hose, you will drain most of the fluid from the radiator (save, I think, the bottom half-inch) and from the bottom of the water pump UP in the engine block. Fully draining the engine block means you'll want to pull the block drain plug - which is, I understand, a huge pain. I haven't done it myself yet, but I've got a spare engine in the garage now, and I've been meaning to pull that plug and see if I can stick some sort of valve in its place (to make things easier for me.)
Distilled water works, but gets a little spendy out here. I have been using "reverse osmosis" filtered water for years with no ill effects - and you may find R/O filtered water to be somewhat cheaper than distilled in quantity (I get it for about thirty cents per gallon in "bulk" - I take in my six-gallon shop bottle and two 2.5-gallon "truck" bottles all at once, and fill them for less than a five-dollar bill. My vehicles get rather more purified water than I do - but I've been drinking tap water all my life, and it hasn't killed me yet. I have had other things do that...)
Considering you won't know how much room you have in the system when you drain it (and I certainly don't keep track!) you may find it easier to mix your coolant in jugs, and then pour it in already mixed. A couple other pointers...
1) If you're going to flush, do that FIRST. Change the hoses/thermostat/whatever after yoiu have flushed, they'll carry crud out with them.
2) If you can find it locally, the use of Redline Water Wetter comes HIGHLY recommended. I won't run without it, and I had consistently good reports from the field before I started using it - in forklifts and generators. That use grew to my own vehicles, and I'm glad I did.
3) Once you start on the cycle, you'll want to change your coolant every two years. If you do a good job with the first flush, subsequent flushes may be easily done with a half-gallon to a gallon of vinegar, and then rinse the system before you drain & fill. Why do you think I want to put a valve in the block drain? Talk about making life easy...
4) If this is your first time flushing this system, or you just don't know how long it's been for this particular vehicle, you'll probably need to do something serious first. In this case, I'll usually use the two-part powder that Prestone makes (if you read the back, it's an acid and a neutraliser.) Follow the instructions EXACTLY, with only one modification - after you flush and neutralise the acid, run an additional "clean water" flush to make sure you get everything out of the system. THEN, drain the water and refill with WW and 50/50. As long as you stick to distilled water or R/O filtered after that, you can get away just fine with a vinegar flush each time after. If you do the "hard flush" with oxalic acid (which is what's in the heavy-duty stuff,) get new hoses and a thermostat while you're getting the flush. Flush, neutralise, rinse, and then change hoses and such - you'll get a lot more crap out of the system that way.
Once I get sorted on how to install an drain valve in the engine, I'll post. Also, if I figure out an easier way to drain the radiator (probably a valve replacement,) I'll post that as well. I'm all for making maintenance as easy as possible - that way, you're more assured of getting it done right...
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