1) With the engine cold, remove the radiator cap and open the radiator drain plug and drain the radiator until it is dry then close the radiator drain plug.

2) Fill the radiator with distilled water. Put the radiator cap back on.

3) With the automobile parked, run the engine with the heater on high at the hottest setting until normal operating temperature is achieved for 10-15 minutes.

4) Repeat Steps #1, #2, and #3 at least three more times until the distilled water in Step #1 drains clear.

5) Drain, fill, and rinse out the coolant overflow tank 3 times with distilled water. I recommend removing the overflow tank while doing this but this is optional.

6) Pour in a bottle of either Zerex Radiator Super Cleaner or Prestone Super Radiator Cleaner into the radiator.

7) Pour in distilled water until the radiator is full then put the radiator cap back on. Fill the overflow tank with distilled water to the "full" or "cold" mark.

8) Drive the automobile for 4-6 hours (can be on and off over a few days). Be sure to constantly check the level of distilled water in both the radiator and overflow tank. Be sure to run the heater on high at the hottest setting all the time if you can stand it. If not, run the heater on high at the hottest setting at least 3 times for 10-15 minutes during the 4-6 hour period.

9) Repeat Steps #1, #2, and #3 at least three more times until the distilled water in Step #1 drains clear.

10) Repeat Step #9 one more time just to be sure the distilled water drains clear.

11) This would be a great time to install a new thermostat and gasket if you know how to do this. Some vehicles do not have a thermostat gasket. If yours has a thermostat gasket, be sure to have a small tube of black gasket sealant. Be sure to correctly apply it to both sides of the thermostat gasket.

12) This would also be a great time to replace that old radiator cap with a new one.

13) With the engine cold, remove the radiator cap and open the radiator drain plug and drain the radiator until it is dry then close the radiator drain plug.

14) Pour in straight coolant sticking with whatever your manufacturer recommends NEVER SUBSTITUTE TO SAVE MONEY! Use enough to achieve no less than a 50/50 mixture of coolant and distilled water but no more than 70/30. Refer to your vehicle's owner's manual for the correct capacity of your cooling system. If you have a 12 quart cooling system, you will need 6 quarts of coolant (1.5 gallons) to achieve a 50/50 mixture of coolant and distilled water. If you want a 70/30 mixture of coolant and distilled water, you will need to pour in about 8 1/2 quarts of coolant (2.125 gallons).

15) With a half full jug of distilled water, fill it up with straight coolant to have a 50/50 diluted mix for top off. Be sure to shake it for about 3-5 seconds so it mixes.

16) Top off both the radiator and overflow tank as needed. Put the radiator cap back on.

17) Keep a watch for any coolant leaks. Repair any coolant leaks immediately.

18) Repeat all of the above steps every 2 years.

I think using a garden hose and a back-flushing tee is a bad idea since city water has additives and chemicals in it such as chlorine, fluoride (except for Indiana), etc. Well water is even worse.

You can get a jug of "Sam's Choice Distilled Water" at Wal-Mart for $.59. It is a good idea to buy a baker's dozen so you have enough. A few more jugs won't hurt anything either especially if you have a large capacity cooling system.

Buy many gallons of distilled water.
Buy two little jugs of Prestone Super Radiator Cleaner (NOT THE FLUSH!).

Basically, drain all the coolant from the radiator (using the tap on the bottom of the radiator) and fill it back up with distilled water. Run the engine until you fill the upper hose turn hot, and then drain the radiator again, and again fill up with distilled water. Continue to do this until the liquid flowing out of the radiator drain is clear.

BTW, make sure when your doing the routine that you have your heater on so you get the stuff out of the heater core as well.

Anyways, once the system is full of clean, distilled water, add the jugs of the cleaner and drive it around for several days (Instructions are on the cleaner bottle).

After the period of time, do the same routine again. Drain radiator and fill with clean, distilled water. Do this until the drain runs clear.

After this, fill radiator with new antifreeze/coolant (pre-mixed stuff is easier to use)...cycle system again, and keep filling and draining until you've put in enough antifreeze to equal the capacity of the system (whatever your manual says).

*This might sound complicated (or confusing), but it's very simple, and will leave you with a spotless coolant system.