You only drained the radiator, the rest of the coolant was in the engine. This is the method that I recommend, it has worked great for me and many others:
For normal system maintanence:
Buy the following:
2 gallons of distilled water $1
2 gallons of Dexcool* $20
Prestone Flush 'N Fill kit $3
Prestone Radiator "Flush" $3
Turn your heater on and leave it on for the entire process
Drain the anitfreeze from the system.
Install the "T" from the Flush 'N Fill kit and follow the directions that came with it.
Disconnect the water hose, close all the drains, add the Prestone Flush, fill with water, get engine up to operating temperature and run for 20 minutes, allow to cool then, drain the system.
Connect your water hose to the Flush 'N Fill "T" and flush one more time. Drain.
Fill the system with a 50/50 mix** of DexCool and distilled water. Continue to fill the system over the next few days as the air is worked out of the system.
For clogged, neglicted, or extremely dirty systems:
Buy the following:
2 gallons of distilled water $1
2 gallons of Dexcool* $20
Prestone Flush 'N Fill kit $3
Prestone Radiator "cleaner" not "flush" $4
Turn your heater on and leave it on for the entire process
Drain the anitfreeze from the system.
Install the "T" from the Flush 'N Fill kit and follow the directions that came with it.
Disconnect the water hose, close all the drains, add the Prestone Cleaner, fill with water, run the engine 3-6 hours (you can leave it in for a few days if neccessary), drain the system.
Connect your water hose to the Flush 'N Fill "T" and flush one more time. Drain.
Fill the system with a 50/50 mix** of DexCool and distilled water. Continue to fill the system over the next few days as the air is worked out of the system.
* If your vehicle was made prior to Memorial Day 1995 or if you don't want to deal with the problems associated with Dexcool, get the standard green antifreeze.
**When you do your final drain and fill....not all the water will come out so to get the proper 50/50 mix you should add the right amount of straight Dexcool then top off with the distilled water.