Flush Engine Coolant 2006 Suburban

the drain plug should be on the inner side of the radiator close to one of the sides. they are often hard to find at first you may need to look from up top or below depends on your lighting.

Thanks for the reply! I will look again with better lighting. Will post a picture when I find this thing. Definately not as obvious as all other vehicles I had in the past.

Here's what I do; take off the air intake hose, remove the lower radiator hose at the thermostat, and the two heater hoses (a mess will ensue), then take a garden hose and put it in the lower radiator hose and backflush the radiator, next, turn both heaters on and use the garden hose to flush both directions on the heaters until the discharge is clear. put it all back together and put enough UNDILUTED dex cool in to make a 50/50 mix (look in the manual for capacities). reason being, the cooling system is now full of clean water. test the antifreeze strength after a day or so.