2007 Toyota sienna 3.5 litrs engine radiator flushing

To drain the coolant using the radiator's petcock you generally get less than half the coolant in the system (about 40-45%). Most shops use a machine to flush a cooling system so they know they can replace it all with new coolant in one step. To do the same at home requires draining and replacing coolant with distilled water in several passes before you can safely assume all coolant has been flushed. Here are steps for at-home coolant flush: 1) Drain radiator via petcock. 2) Fill radiator with deionized or distilled water. 3) Run engine up to temperature until thermostat opens (with heater on). 4) Let engine cool a few minutes, then carefully open radiator cap. 5) Drain radiator again. Flushed coolant should be diluted due to the added water in step 2. Tighten petcock. 6) Allow engine to cool and go back to step 2. 7) Repeat steps 2 thru 6 three or four cycles. The drained coolant should be nearly all water by this point. 8) When satisfied (or just tired of repeating the procedure), add between 3 and 4 quarts of CONCENTRATED coolant (not the pre-mix stuff) to the radiator. There will still be 3 qts or so of almost pure distilled water in there from the above steps. 9) Don't forget to drain and replenish the coolant reservoir as well. Just be sure to use distilled or deionized water and not tap water, and to BURP or bleed air from the system when all is said and done.