Flushing the Radiator - in progress
 

this is what I did

1. drain the radiator
2. let the hose water run for a while
3a. plug back up the bottom and pour the prestone
3b. added water to the rim
4. full blasted my heater and idled for about 10 min.
5. drained the rad, again and let the water run through
6. plugged it up and poured my 2nd bottle of prestone (not the flush, but the
rad cleaning solution). Added water to the rim
7. It says to drive around for 3~6 hours
8a. I'll be draining it again
8b. let the water run
8c. plug it, fill it with water and let it idle for 10 min with heater on full blast
9. fill up with 50/50 coolant

question: how big is our rad? solution said to use 2 bottle, if more than 4 quarts..
I'm doing this 2x, since I have high mileage and it hasn't been done since 90k.

Cooling system capacity in my 2001 4Runner with the 3.4 is 9 litres, I would think a 1999 would be similar.

And be careful with only water and rad cleaner in there, you don't want it to freeze.

i'm doing this process right now too...because it's sooo hard to get to the drain plugs near the engine mount...how do i be sure that i'm getting the water out?

i'm moving to montana this month (october) right in the cold part and don't want stuff to freeze in there. any advice on how to ensure I flush all the water out please...

nevermind...found some good posts here.