I miss the old days of installing the T and using a hose to flush the system. But if you live in an urban, tree hugging part of the country like I do, those days are gone. And I guess it is only right. Dirty coolant running down the drive, into the storm drain, ends up in the streams, rivers, and in my area, the Puget Sound.
I used a big plastic tub and drained the radiator. then I dump that into a 5 gallon bucket and haul it to a collection site. You will only get about 1.5 gallons out that way. the system holds just under 4 gallons. The more hoses you want to disconnect, the more you will get out. Some people even remove freeze plugs, but no way I am going down that road, lol
I then put in some Prestone flush, and filled with distilled water. Leave the cap off, and run the engine, or drive it. It will burp after the thermostat opens, and you will need to add more water. I then drove the car for a few days. Drained again, then refilled with distilled water, and drove it a day.
The next drain should be pretty clean, mine wasn't, and I ended up draining and refilling many, many times. lol
After the final drain, you need to get about 2 gallons of pure antifreeze in to get to a 50/50 mix. Just draining the radiator will not give you that much room. I also removed the lower radiator hose, but that did not drain enough on mine. I got about 1 and 2/3 gallons in. I am ok with that, because of our mild climate here, it is not too hot or cold.
It you want to use the T, don't cut your heater hose. Get a 2 foot piece of 3/8 inch hose. Remove on of the heater hoses at the firewall. Plug the T into that hose, put the 2 foot piece on the other side of the T and connect that spare hose to the firewall heater core connection. Then follow the instructions they give you.
Hope that helps
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