Your coolant is getting some age on it. The heater is not as warm as it used to be. You have noticed a slight nudge upward on the car’s temperature gauge. These may be signs that it is time to give your cooling system a good flushing. As a mechanic for 5 years, I had many opportunities to flush cooling systems.
What happens when the cooling system is flushed?
Essentially, flushing the cooling system removes most of the old coolant and replaces it with fresh coolant. At the same time, it can help the heater core and radiator shed some of the plaque that may have built up over time. You can purchase flush kits, but these are not usually any more beneficial that the method described here.
Locate drain valve on bottom of radiator.
The first step in the flushing process is to remove a large portion of the old coolant. The easiest way to accomplish this is to drain it from the system. On the bottom of your radiator will be a drain valve. It will be either to the far left or far right side of the lower part of the radiator. Some in the front, and some are in the back. It will look like a small simple faucet. Most of the time you can turn the valve by hand to release the coolant. Make sure the engine is cool enough to keep you from getting scalded by hot liquid.
Use a pan or bucket to catch fluid drained from cooling system.
Antifreeze is lethal to all animals and people. Catch the antifreeze so that it is not contaminating nature. It tastes sweet. Resist the temptation to lick off of your fingers. It really can make you go blind.
Dispose of old coolant if you do not plan to reuse it.
Try to have a disposal plan in place for the old coolant before you begin the flush process. If you are unable to determine the best way to get rid of it, secure some containers that can be marked and sealed until you can dispose of the fluid safely. Use this same process during any subsequent flushing steps since some antifreeze will in the water drained from the engine after the flush.
Refill system with water and add a container radiator flush if desired.
If you are using a product to assist with your system flush, follow the instructions on the container regarding when and how much to add. Pour or run water into the radiator to refill the system with fluid. Leave the radiator cap off and start the car. Continue to add water until the radiator remains full with the liquid circulating in the system.
Make sure radiator cap is secure and turn the heater on high.
Let the car run for about 15 minutes after it is warmed up. Turn the car off and let the engine cool for about 30 minutes. Once the engine has cooled enough to reduce the chance of burns when you work on it. Go on to the next step.
Drain water and coolant from radiator.
Use the same process as you did to start the cooling system flush to remove the liquid from the radiator and lower portion of the engine. Follow the same safety precautions for dealing with fluid that you drain.
Repeat the process if you believe the system needs additional cleaning.
Unless you believe that more is always better, one good flushing should be enough. If your coolant is very old (10 years since a flush), you might choose to give the system a second round of flushing.
After completing the flush, refill the system with the coolant and water mix recommended by the manufacturer.
Make sure that you get the system completely filled. Most cars use a 50/50 mixture of antifreeze to water. If you buy the premixed coolant, this ratio should already be set for you to just pour it straight from the jug into your system.