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How to Change Coolant


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An Engine Coolant Change Is a Beginner Level Repair for Most DIYers. Here’s Everything You Need to Know to Drain and Fill or Flush Your Engine Coolant In Less Than An Hour.

  • DIY Difficulty Level: Beginner
  • Time Required: less than 1 hour
  • Tools & Materials

  • Drain pan
  • Pliers
  • Funnel  

What Is An Engine Coolant Change?

front view of engineChanging your coolant helps keep your engine cool.

Engine’s run at extremely high temperatures, and coolant is used to keep these temperatures at specific levels for optimal engine performance and prevent overheating. In its simplest explanation, the coolant system consists of the radiator and water pump, which takes hot coolant from the engine, cools it down and then returns it to the engine. There are other components such as the thermostat and heater core, as well. 

Over time, the engine coolant breaks down, which not only affects the ability to keep the engine in the proper temperature range, but it also can cause corrosion or excessive wear on the rest of the system including the hose. An engine coolant change replaces the old coolant with new coolant to keep your engine running at the proper temperature.

Engine Coolant Drain and Fill Versus Coolant Flush?  

Changing the engine coolant can be done in two different ways: a simple drain and fill and a more in-depth coolant flush. As its name suggests, a coolant drain and fill consists of just draining as much fluid from the system as possible and then filling it up with new fluid. 

A coolant flush is another version of an engine coolant change, but instead of relying on gravity to drain the coolant, you pump water through the entire system flushing out the engine block, heater core, and hoses. 

Is It Safe to Drive with Old Engine Coolant?  

Unless your cooling system is in bad shape, chances are it won’t affect the safety of your vehicle. In worst-case scenarios, failing to change engine coolant can result in added repair costs down the road and, in extreme cases, being left stranded with a broken-down vehicle.

What happens if You Don’t Change Your Engine Coolant?

If you don’t change the engine coolant every 30,000, it’s probably not going to be the end of the world. That being said, failing to properly service the coolant system can result in overheating, which could lead to severe engine damage such as a blown head gasket.

The engine coolant is what prevents your engine from overheating, so you definitely don’t want to forget about this service. The average cost to change engine coolant at the shop is estimated to be between $98-$123. However, this is an easy job for beginner DIYers, and those willing to undertake this service should expect the job to take less than an hour to complete. Plus, doing this yourself could save upwards of $100 in labor costs!

When to Change Engine Coolant?

How often should you replace your engine coolant? 

Coolant service recommendations vary by automaker as well as vehicle type and severity of duty, but generally speaking, most vehicles should have the coolant changed every 30,000 miles or so. 

If you don’t know when the last time the coolant was changed, a quick visual inspection will help. With the engine cold, remove the radiator cap and look at the fluid, but keep in mind that not all coolant is green. If the coolant level is low, you can just top it off, but if the coolant looks dirty, dark or rusty, then you should perform a coolant service as soon as possible. 

How do you know when it’s time to have this done or do it yourself?

Changing engine coolant is a very easy job, but sometimes it’s hard to access the drain valve or get it open. Since most valves are plastic, don’t be too aggressive when it comes to turning the drain valve as that could result in a broken valve. 

What Are Common Symptoms Indicating You Change Engine Coolant?

  • Mileage determined by manufacturer’s preventative maintenance schedule
  • Visual inspection shows discolored engine coolant

How To Change Engine Coolant  

Step 1: Drain Coolant 

radiator cap offBefore changing your coolant, make sure the engine is cold and take off the radiator cap.

Before attempting to change your engine coolant, make sure the engine is cold and remove the radiator cap. 

In order to drain the coolant, you must be able to access the bottom of the radiator. This means that on some vehicles that sit closer to the ground, it may require the use of a jack to fit under the car to do so. Once you’ve accessed the bottom side of the radiator, locate the petcock valve. 

Position a drain pan under the valve and then open the valve; sometimes you might need a pair of pliers for added grip to turn the valve.

Step 2 (optional): Flush engine coolant system

engine coolant draining on carEngine coolant draining from vehicle

Simply draining and refilling the engine’s coolant is good enough in most situations, but if you want to do a coolant system flush, then this extra step is easy. You should flush the system if the old coolant was in bad shape or if there was any debris in the coolant. To flush the system, keep the radiator valve open and the drain pan in place, and then run water through the radiator. You can either do this with a garden hose or by pouring containers full of water. Do this until clean water comes out of the drain, and then let as much of the water drain out as possible.

Step 3: Close radiator drain valve 

radiator drain valve on carEngine coolant will drain from the radiator drain valve. When finished, make sure this valve is closed.

Once all the fluid has been drained from the radiator, close the drain valve.

Step 4: Top off coolant and overflow reservoir

use a funnel to fill radiator with new engine coolantTop off coolant using a funnel to fill the radiator.

With the valve closed, now it’s time to add new engine coolant. Using an adapter like the one pictured here is helpful in preventing air bubbles in the system, but it isn’t required. Once the radiator seems full, start the engine and let it run until it gets up to temperature. Usually, the coolant level will drop once the thermostat opens, and then you can top off the radiator.

At this point, fill the coolant overflow reservoir to the proper level. Keep in mind that some coolant modern vehicles combine the overflow and fill area, so this last step isn’t always required.

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Jeffrey N. Ross

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.

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About the Author

Jeffrey N. Ross

Jeffrey N. Ross

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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