usually there is no sound that indicates your coolant needs changing. that type of sound could be from air in your coolant system though, if that's the case it needs to be burped. as for burping the system thats a real pain in the @ss. its not like a normal system were you just put coolant in while the car's running. there should actually be a sticker on the underside of your hood with directions for changing coolant.
I don't about you guys, but underneath my hood, there is a sticker there with illustration on how to replace the coolant.
(*Make sure you are parked on a flat, level ground*)
Simplest way taught to me by my local mechanic shop:
To replace coolant, jack up the car, put on jackstands, take off the radiator cap, locate the coolant drain bolt on the lower part of the radiator, untighten the coolant drain bolt but don't loosen it, lower the car, now remove the plug and let the coolant drain out. (*make sure you something to catch the old coolant*)
-This next step is OPTIONAL, use a waterhose, run the water, place the hose the radiator cap opening, have a friend turn on the engine, and let it flush until you see the coolant existing the drain plug hole turns into water. This step is optional but it helps take out all the old coolant and any dirt or crap in there.
*Almost all mechanic shops do not do this step because if would be time consuming and a mess in the shop, they just drain the coolant and refill it*
-Once it's clear, put back the drain plug, and tighten it. Then refill with 50/50 mix coolant/water. Best is to buy the Toyota coolant if you can, it's premix 50/50 or the aftermarket brand like Prestone.
One more thing I forget to mention for you newbies but it is really common sense.
Make sure you have the water house running at ALL TIMES. Turn off the engine before you turn of the water hose. Turning off the water hose and and letting the engine run can lead to....... :ugh: *You get the point*.
Draining as you describe will only drain the fluid out of the radiator. There still is a good amount of fluid in all the hoses, the water pump..... So if you then add 50% water and 50% coolant, you'll probably end up with 75% water in your system. I've been told it's not worth it to flush with water, just drain as much as you can and refill.
I have always done it the way mickey513 described, but I always use straight coolant after flusing it with the water. Not the 50/50 mixture coolant because they are only good for the drain and refill-method. Does are only good if you do just the drain and refill method.