Changing coolant is a task you can do yourself with basic tools and about an hour of time
Coolant keeps your engine from overheating and from freezing in cold weather. Over time, coolant breaks down and loses its ability to protect your engine, which is why manufacturers recommend changing it every 30,000 to 100,000 miles depending on the type and your vehicle. The process involves draining the old coolant, flushing the system, and refilling it with fresh coolant mixed with distilled water.
You do not need special training or expensive equipment. A socket wrench set, a drain pan, a funnel, and the correct coolant for your vehicle are the main things you'll need. The hardest part is usually finding the drain plug and letting the system cool down enough to work safely — coolant stays hot long after the engine shuts off.
Key Takeaways
- Let your engine cool for at least an hour after running before you open the cooling system, because hot coolant can cause serious burns.
- Check your owner's manual or a parts store to find out which coolant type your vehicle needs, because mixing types can damage your engine.
- The drain plug is usually on the bottom or side of the radiator, and you'll need a drain pan underneath to catch the old coolant.
- After draining, flush the system with distilled water until the water runs clear, then refill with the correct coolant-to-water ratio for your climate.
- Bleed air from the system by running the engine with the radiator cap off until the coolant level stops dropping, then top it off and replace the cap.
Gather the right coolant type before you start
Different vehicles use different coolant types, and mixing them can cause corrosion inside your engine. The most common types are green (traditional), orange (extended-life), pink (Dex-Cool), and blue, but your vehicle may use something else. Check your owner's manual in the maintenance section, or call your car's dealership parts department with your vehicle identification number (VIN) and ask what coolant to buy.
You will also need distilled water to mix with the coolant. Most coolants come as a concentrate that you dilute 50/50 with distilled water, though some come pre-mixed. Read the label on the bottle to see which you have. If you live somewhere very cold, you may need a higher concentration of coolant to lower the freezing point; if you live somewhere very hot, you may need less. Your owner's manual will specify the ratio for your climate.
Buy enough coolant to fill your entire system. Most vehicles hold between one and two gallons, but check your manual to be sure. It is better to have extra than to run short halfway through and have to stop.
Let the engine cool completely before opening the system
This step is the most important for your safety. Coolant circulates through the engine under pressure and stays extremely hot even after the engine shuts off. Opening the radiator cap or drain plug on a hot system can cause the coolant to spray out and burn your skin and eyes. Wait at least one hour after the engine has been running, or longer if you drove hard or in hot weather.
A safe test is to touch the radiator hose with the back of your hand. If you can hold it there comfortably for several seconds, the system is cool enough to work on. If it is too hot to touch, wait longer.
Drain the old coolant from the radiator and engine block
Place your drain pan under the radiator. The drain plug is usually a bolt or valve on the bottom or lower side of the radiator. Loosen it with your socket wrench by turning counterclockwise. Once it is loose enough, you can usually unscrew it by hand. Let the old coolant drain completely into the pan — this can take several minutes.
Some vehicles also have a drain plug on the engine block itself, usually on the side facing the radiator. Check your owner's manual to see if yours does. If it does, drain that as well into the same pan. Once both are empty, reinstall the drain plugs and tighten them snugly, but do not over-tighten or you may strip the threads.
Dispose of the old coolant properly. Most auto parts stores and service stations will take it for free, and many municipalities have hazardous waste collection days. Never pour coolant down the drain or into the ground — it is toxic to animals and the environment.
Flush the system with distilled water
Flushing removes rust, sediment, and old coolant residue that can clog your new coolant and reduce its effectiveness. Remove the radiator cap and pour distilled water into the radiator opening until it is full. Replace the cap, start the engine, and let it run for about five minutes with the heater on high. This circulates the water through the entire system.
Turn off the engine, let it cool for 15 minutes, then drain the water the same way you drained the old coolant. Repeat this process two or three times until the water coming out is clear instead of brown or rusty-looking. This usually takes three flushes, but heavily contaminated systems may need more.
Refill with new coolant at the correct ratio
Mix your coolant and distilled water according to the instructions on the bottle and your owner's manual. The standard ratio is 50/50, but check both sources to be sure. Pour the mixture into the radiator opening using a funnel until the radiator is full, then replace the cap.
If your vehicle has a separate coolant overflow tank (a translucent plastic container near the radiator), fill that to the "cold" line marked on the side. Do not fill it to the "hot" line yet — that level is for when the engine is running and the coolant has expanded.
Bleed air from the cooling system
Air pockets in the cooling system can prevent coolant from circulating properly and cause overheating. To remove them, start the engine with the radiator cap off and let it run until the engine reaches normal operating temperature. You will see the coolant level drop as air bubbles escape and the coolant expands. Once the level stops dropping and you see coolant flowing in the radiator, turn off the engine.
Let the engine cool for 15 minutes, then top off the radiator with more coolant mixture until it is full. Replace the radiator cap. Check the overflow tank and top it off to the "cold" line if needed. Start the engine again and let it run for a few minutes to make sure the temperature gauge stays in the normal range and the heater blows hot air.
Check your work and monitor for leaks
After you finish, inspect the radiator drain plug and any engine block drain plugs to make sure they are tight and not leaking. Look underneath the vehicle after it has been parked for a few hours to see if any coolant has dripped. A small amount of seepage is normal, but a steady drip means a plug needs to be tightened or replaced.
Drive the vehicle for a short distance and then check the coolant level again after it cools. It should not have dropped noticeably. If it has, you may have an air pocket that needs more bleeding, or there may be a leak you did not see. Run through the bleeding process again if the level dropped significantly.
Frequently Asked Questions
Can I mix different coolant colors?
No. Different colors usually indicate different chemical formulas, and mixing them can cause corrosion and sludge inside your engine. Stick to the type your owner's manual specifies. If you are unsure what is currently in your system, drain it completely and start fresh rather than guessing.
What if coolant leaks out while I am draining?
This is normal — some will splash or drip as you remove the drain plug. That is why you use a drain pan. If you spill some on the ground, clean it up with paper towels and dispose of them with the old coolant. Wipe the area with water if you have it available, because coolant is slippery and toxic.
How do I know if I have the right coolant-to-water ratio?
The bottle label will tell you the ratio, and your owner's manual will confirm it. Most are 50/50, but some extended-life coolants are different. If you are mixing concentrate, use a measuring cup to get it right. Pre-mixed coolant does not need dilution — use it straight from the bottle.
Why is my heater blowing cold air after I change the coolant?
This usually means there is an air pocket in the heater core. Run through the bleeding process again, making sure the engine reaches full operating temperature with the radiator cap off. The air should escape as the coolant circulates and expands.
How often do I need to change coolant?
Most manufacturers recommend every 30,000 to 100,000 miles depending on the coolant type and your vehicle. Check your owner's manual for the specific interval. Some newer vehicles use extended-life coolant that lasts longer, while older vehicles may need more frequent changes.