How to Change Coolant in Your Car

Changing Coolant in Older Vehicles

Draining and filling the engine coolant is fairly straightforward for most vehicles produced before 2000.

Inspect the coolant

• Start by checking the condition of your coolant when the engine is cool.
• Remove the radiator or coolant reservoir cap and examine the coolant color. If it looks rusty (don’t confuse orange coolant with rust), has crud or oil floating on the top, or looks like chocolate milk, call it quits and take it to a pro. You have problems that this procedure won’t solve.

canvcanv

Prepare to change your coolant

• Raise and safely support the front end of your car on jack stands.
• Place a large drain pan under the radiator and remove the radiator cap. If your radiator doesn’t have a cap, remove the pressure cap from the coolant tank.

Drain the radiator

• Open the drain petcock on the bottom of your radiator.
• Not all petcocks open the same way. Open yours by either unscrewing, twisting a quarter turn, or twisting and pulling.
• Various styles of petcocks are shown in the photo at the end of this article.

TMB Studio

Remove the lower coolant hose

• Loosen the lower radiator hose clamp with pliers (spring-type clamp) or screwdriver (worm-drive clamp) and remove the hose.
• Pull the hose free and drain the remaining coolant. If the hose doesn’t budge, use a hose removal tool to break it loose.
• Reconnect and clamp the radiator hose and reinstall the drain petcock after draining.

TMB Studio

Drain the engine block

• Locate and remove the block drain plugs (they’re in a different spot on every engine, so refer to a repair manual for the location of yours.
• Once the block has drained of coolant, reinstall the block drain plugs and move on to the refilling step.

Add coolant

• Determine the capacity of your vehicle’s engine before adding the mix to the radiator, and always follow the coolant manufacturer’s directions when diluting concentrated coolant.
• Stir the full-strength (not premixed) coolant and distilled water together in a clean bucket. Using distilled water prevents mineral deposits on internal engine and radiator surfaces—never use tap water. Pro Tip: Leave the car raised while you refill the radiator to allow air pockets to escape from the engine.
• Slowly fill the radiator or coolant tank with fresh coolant until the coolant is 1 in. below the neck of the radiator or a few inches below the full mark on the coolant tank. Start the engine and let it run.
• After the engine warms, you’ll see the coolant level quickly drop in the radiator/coolant tank. That means the thermostat has opened, and it’s time to add more coolant to bring the level to the top of the radiator, or to the “HOT” mark on the coolant tank. Check your owner’s manual or service manual to see if your car requires a special air bleeding procedure.
• Check for leaks, shut off the engine, install the radiator cap, lower the car, and go for a spin.

TMB Studio

Changing Coolant on Newer Vehicles

Start by buying the type of coolant listed in your owner’s manual. If your manual calls for an “extended life” coolant unavailable at the auto parts store, buy it from the dealer. Don’t buy a “universal” coolant. Using the wrong coolant can cause premature component failure and void your warranty.

The AirLift II Economy Cooling System Refiller was used for this procedure.

Remove the lower hose

• Slip the pointed end of the removal tool all the way into the end of the hose and pull it around the radiator neck to break the hose loose.
• Pull it off quickly and immediately direct the coolant into the drain pan.

Pull a vacuum on the system

• Insert the air tool into the radiator neck or overflow bottle.
• Connect the exhaust hose and compressed air line. Route the open end of the tool’s exhaust hose into an empty gallon jug or pail.
• Open the valve and let the vacuum rise until the needle reaches the edge of the red zone on the gauge.

Refilling car with fresh coolant:

• Insert the fill tube into the coolant bottle and open the valve to let the vacuum suck fresh coolant into the system.
• Repeat the procedure until the system is full.
• Reinstall the radiator or overflow tank caps, remove the jack stands, lower the vehicle back down and go for a spin.

TMB Studio

When to do a complete flush

If you’re way past due for a coolant change and your cooling system is corroded, you should take your car in for a professional flush. The same is true if you’ve mixed different types of coolant in your radiator. But if you’re on schedule for a coolant change and your coolant is free of brown, gunky corrosion (extract a little coolant with a baster to examine it), you can skip the flush procedure and perform a simple drain and refill operation yourself and save money.

Drain petcocks

Drain petcocks come in several different styles—screw threads, quarter-turn twist, and quarter-turn and pull. Plastic drain petcocks become brittle with age and can break easily, especially if you try to unscrew a quarter-turn twist style. As a precaution, buy a replacement drain petcock at the auto parts store before you begin the job. They only cost a few dollars; return it if you don’t need it.

TMB Studio

Buying the right coolant

Most DIYers buy coolant at the auto parts store because the label says it’s “universal,” meaning it works in all cars. The carmakers disagree. Over the past several years, they’ve issued service bulletins warning that “universal” coolants are often incompatible with the newer metal alloys, gaskets and seals used in their vehicles. The carmakers aren’t saying that just to increase sales of their proprietary coolants. They’re seeing real (and expensive) damage caused by these coolants.

If you use the wrong coolant, you won’t see the damage for a few years. But when you do, it’ll cost you a bundle. So heed the manufacturer’s warnings and buy coolant right from the dealer. It’ll cost about $6 more per gallon (most vehicles only need 2 gallons), but the peace of mind is worth it.

Replace the thermostat and radiator cap

The thermostat is the single most important component in your vehicle’s cooling system because it regulates engine temperature. A failed thermostat is the second most common cause of engine overheating and engine failure (a failed radiator fan is No. 1). Despite this, most owners often never replace it. Changing a thermostat yourself takes less than an hour (unless it’s buried). To find out how to replace yours, learn how to replace a thermostat. But if yours is inaccessible, pay a shop to replace it.

And a worn radiator cap (sometimes it’s on the overflow tank) can also contribute to engine overheating. The good news is it’s a snap to change. It’s just a matter of unscrewing it and replacing it with a new one.

Both parts are inexpensive (about $12 each at any auto parts store) and are cheap insurance against overheating. They don’t need to be replaced every time you change your coolant, but if they’re old, give yourself some piece of mind and replace them with new parts.

TMB Studio

FAQs

Will a car run better after a coolant flush?

Yes. A coolant flush removes poor-performing coolant in addition to any sludge or buildup contributing to an under-performing cooling system and keeps your engine running in its optimal operating temperature window.

Does coolant affect AC in a car?

Not in the summer, but in the winter, absolutely! The coolant system is completely separate from the air cooling system in the engine bay, but it is directly related to the cabin heater. If you don’t have good heat in the winter, your coolant system may need a proper flush, including a heater core flush.

Is antifreeze the same as coolant?

These terms are often used interchangeably, which is fine for modern cars, but they don’t exactly mean the same thing.

If you fill your car’s radiator with straight water, that would be considered “coolant.” Water is very good at removing heat; however, to keep it from freezing, an “antifreeze” is added in the form of propylene glycol or ethylene glycol. This lowers the freezing temperature of water and, as a bonus, increases the boiling point. This mixture can be referred to as coolant or antifreeze, but it’s actually a blend of both.