The engine drain plug on a 22RE it just below the exhaust manifold towards the back of the engine under cylinder 3 or 4, it is just a bolt. There are 2 hoses that go from the engine to the firewall, those are the heater hoses.
How thoughtful of you to take the time and post these pics. As many of you know, the pics/diagrams/explanations in the aftermarket manuals (Haynes et al) are often pretty lame at best.Hey well no one ever really answered this guy. I recently bought a 1992 pickup with a 22re and had the very same question - I searched and searched and it took me quite awhile to find a definite answer, but I figured it out. So I though I would be nice and help out the next person with this question.
Here are some pictures. The part labeled "3" is the heater valve - it links to the hot/cold lever inside the cab and controls how much hot water flows through the heater core. Therefore, this hose - "2" ( blue line) is the "heater core inlet hose". The hose numbered "1" (red line) is the outlet hose. Connecting a flush kit to this line would not flush the system properly, it would be forcing water from your hose in the wrong direction to the heater core.
The two hoses were zip tied together, and it was better to remove the zip tie to do this. In the second picture, you can see that I zip tied the outlet hose temporarily away from the area to avoid damaging it. You can see where I placed the "T". The third picture just shows the complete job - after I zip tied the hoses back together. Don't forget to open the heater core valve (by turning the heater to the highest setting), before flushing. This is critical. Also remove the radiator cap, and open the radiator drain valve. Turn the hose on and let the engine run until the water runs clear.
Hope this has helped someone else.
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