Your cooling system should be flushed every other year. No, I'm not crazy, but with all the new chemicals they use today, it will literally eat up the rubber hoses and deteriorate the heater core, and the radiator core.
Have a drain pan under the drain plug, or the lower radiator hose, to catch the old fluid. EPA
doesn't want you to let it run out onto the ground — it will contaminate Earth!
If you want, and it's much faster, you can remove the lower radiator hose from the radiator. Use caution, though, you don't want to break the neck on the radiator — that's a no-no. It is better to have the drain plug opened, though, when you start to flush. A word of caution!
Antifreeze/summer coolant is very toxic. Don't get it on the body paint, or on your skin. Wash it off with water! Another thing, it will kill your pets if they drink it, so keep them, and children, away from it, remember, I warned you! Some vehicles have a vent plug. It's located near the thermostat housing (where the upper radiator hose is connected to). Open this to vent: the fluid will empty out better.
Now will be a good time to inspect the hoses. Look at the heater hoses: are they swelled near the clamps? Do they feel hard, or real soft? If so, replace them. The same with the upper and lower radiator hoses.
If your vehicle has a by-pass hose (from the water pump to the thermostat housing) check it also. Don't be skimpy here, a little for a hose now will save a lot later. Replace the hose clamps, too, if they need replacing. I hate those "clip" types, and they are usually in need of replacing.
You can get a "flush kit" at most auto parts stores. Read the instruction as to how to install it. Most of the time you can cut the heater hose going to the waterpump and install it there. They are designed to be a permanent fixture: you can leave it hooked up.
After you have installed the flush kit you need to hook up the garden hose to the fitting. It might be best for you to remove the thermostat, as cool water will close it and restrict flow.
Turn the water faucet on, not too much, and leave the radiator cap off and the drain open. If water spews from the vent plug opening, put it back in.
Crank the engine and let it idle. Watch the fluid coming from the 3/8 tubing. When the fluid is clear as water, ha,
you can turn the faucet off and then turn the ignition switch off.
You may need two drain pans to catch all the fluid, plus, you will need to find a place in your city to dispose the fluid: a repair shop, or disposal plant. Do not pour it out on the ground
Let the vehicle cool down. After the engine is cold you can turn the water faucet on again and reflush. There is no need to restart the engine, just let the water run through the block, heater core, and radiator. Let this go for about two or three minutes, then you can turn the water off and remove the garden hose. Put the cap that came with the kit over the spout after you remove the garden hose ... you won't have to remove the flush kit, just leave it there for the next time.
They make chemicals to flush systems that have a lot of rust and deposits in them, but this procedure will work in most cases.
Be sure you have the lower radiator hose clamp tight (if you removed it), and have the drain plug tight (remove the hose if you put one on).
Now you can add your antifreeze/summer coolant. Depending on where you live, most vehicle manufacturers recommend a 50/50 solution. Look in your owner's manual and see what they recommend. If your vehicle holds two gallons of coolant, then you want to put in one gallon of coolant and one gallon of water.
If your vehicle doesn't have a vent plug, you can fill the radiator to the top, then crank the engine. Note:
If you removed the thermostat, be sure to reinstall it; I'd recommend installing a new one.
After you crank the engine, let it idle. Watch the radiator filler spout, water may overflow. If it does, put the cap back on. Feel of the upper radiator hose. When it gets warm to hot, then the thermostat has opened and you can remove the radiator cap slowly. If no water tries to escape, then you can remove it and add water.
Most vehicles of late have a plastic reservoir. After you have the radiator full you can fill the reservoir to the line on the side of the container, "full cold", with water.
Now, start the engine again and let it idle. Look for leaks (repair them if you have any) and watch the temperture guage. If you have a light you will have to feel of the upper radiator hose to tell when the engine is at operating temperture: the hose will be very hot.
Most vehicles run a 190° thermostat, so you won't be able to hold the hose very long. No leaks?
Fluid level full?