If there is any light you should be attentive of it is the low coolant light for sure. When the light comes on there may be no immediate danger that would require you to abandon your vehicle, but stopping your car is heavily recommended. Continually driving with a low coolant light on could cause severe damage to the internals of the engine.

What Is the Importance of the Engine Coolant?

Before addressing the reasons for your low coolant light to illuminate, it is important to understand exactly what engine coolant is and the importance of keeping it filled in your vehicle.

What is Engine Coolant / What is Radiator Coolant

Engine Coolant is a fluid that absorbs the heat within the engine and then travels to the radiator to cool. The coolant is a mixture of anti-freeze and water.

When vehicles are actively operating, they tend to create a large amount of energy by burning up the gas in the fuel tank. This energy is divided between allowing the vehicle to accelerate forward and the remainder of the energy is converted to heat. This heat is either expelled through the exhaust while some remains inside the engine block.

Since so much heat is dispersed when operating car engines, they require a way of cooling down, or else the internal engines will melt from the inside out. This is where the engine coolant, a water-based solution, comes in handy to absorb the heat from the engine.  Since the engine coolant becomes hot, it is transferred to a radiator located at the front of the vehicle. This transfer will allow the coolant to sit stationary inside of the radiator in front of the outward facing vents to be cooled by the air as you drive your vehicle.

Because the composition of engine coolant is comprised of water and antifreeze you will notice its bright colors. Manufacturers purposely make the coolant vibrant colors so there is no confusing a leak, as coolant is an important component to maintain a healthy engine.

What Causes Low Coolant Light to Come On?

There could be a plethora of reasons as to why your low coolant light comes on, as the system in which it runs is exceptionally complex. The safest way to ensure you find the solution the first time is to bring your vehicle to a mechanic. Though, it’s worth it to troubleshoot your own vehicle before bringing it into a repair shop to see if you can resolve the issue yourself.

Your Coolant Level Is Low: How to Check Coolant Level

If you notice your coolant level low but no leak there is a chance you have ran through your remaining coolant. The easiest way how to fix low coolant is to begin filling your coolant back to acceptable levels and allow the coolant to soak back into the system.  Upon opening your radiator cap, you will see indicators such as “max” and “min” which indicates the level of the coolant mixture currently in your tank. Simply filling your vehicle’s tank to an acceptable level (underneath the “max” line) should solve the low coolant issue; though constant monitoring for the week after filling it is recommended to ensure there is no coolant leaking.

Checking Coolant Health/Quality

If your car is past due for a coolant change, or if your low coolant light comes on, there is a good chance that your cooling system has corroded. If this is the case you should take your car for a professional coolant flush, especially if you’ve mixed different types of radiator coolant.

Usually you check if your coolant is bad before even bringing it in for a flush by extracting some of the existing coolant with a baster and examining it. If there is evidence of corrosion or gunk build up, you are in need of a full-service flushing. When performing routine maintenance on your vehicle, we always suggest to check coolant level. In doing so, you can essentially save yourself money by negating the need for a full-service flush. The following is a guide of best practices to ensure you’ll never be spending unnecessary money due to neglect of your vehicle’s systems.

Buying the Right Coolant for your Vehicle

The first steps for dealing with your vehicle’s coolant is simply to buy the type of coolant listed in your owner’s manual. As obvious and redundant as this sounds, many individuals purchase the incorrect type of coolant and are forced to pay for a full-service flush.

When you are at the local parts shop to purchase the correct coolant, you will also need to purchase a drain cock. The drain cock is a part used to extract liquid from the lowest part of the tank, as any remaining coolant left behind will have a chance to corrupt the new coolant poured into the tank. If your manual calls for an “extended life” coolant that isn’t available at the auto parts, you can always buy it direct from the dealer.

Regardless of where you purchase the coolant from don’t ever purchase a “Universal” coolant fluid. Using the wrong coolant can cause premature /component failure and void your warranty. The proper car care will always make the differences.

How to Change Coolant Yourself: How to do a Coolant Flush

The next step in the process will most certainly become the part where most will disassociate themselves from the repair, but for those inclined enough to proceed you will need to go underneath the car. In perpetration to drain the car you will need to rise, and safely support, the front end of your vehicle with a car jack, and then prop your vehicle on jack stands to ensure stability.

How to Drain Engine Coolant / How to Drain Radiator

At this point you will place a large drain pan (a large bowl will work in place of a drain pan) under the radiator cap. Some radiators may not have a cap, in this case you would just find and remove the pressure cap typically located next to the coolant tank. Then proceed to open the draincock and drain the radiator.

Once all the fluid is drained from the coolant tank and the draincock is out, loosen the lower radiator hose clamp and disconnect the hose from the engine to drain the rest of the coolant. You may need to remove clamps during the process, in this case slip-joint pliers are the best tool to remove clamps, especially spring-loaded clamps. This will then empty out the rest of the coolant and provide you the ability to add new coolant. Lastly, reconnect and clamp the radiator hose and reinstall/replace the draincock after draining.

Now we are onto filling the coolant tank. When performing this procedure leave the car raised while you refill the radiator to reduce the possibility of air pockets forming in the engine. Now that your coolant is drained, make sure to follow the coolant manufacturer’s directions for diluting concentrated coolant.

How to mix Anti-Freeze Coolant with Water

Mix the anti-freeze coolant and water thoroughly in a clean bucket in order to prevent mineral deposits on internal engine and radiator surfaces. When mixing the coolant with water always use distilled water—never tap water, as it may cause mineralization to the coolant. Slowly fill the radiator or coolant tank with fresh coolant until the coolant is one-inch below the neck of the radiator, or a few inches below the full mark on the coolant tank.

Filling up Engine Coolant / Finishing Coolant Flush

Start the engine and let it run in idle, 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. The last steps of this process are to check for any leaks, shut off the engine, install the cap, lower the car, and go for a drive.

Do I Have a Coolant Leak?: Car Leaking Coolant

If you notice your low coolant light on after starting up your vehicle for the first time you may have a coolant leak. One of the easiest ways to confirm this is by placing your vehicle in neutral and pushing it back to look underneath the area where the car is parked.  It’s important that you push the car rather than drive it, as if your car is low on coolant the engine block could potentially crack, costing you thousands.

Since coolant is manufactured as a vibrant color you will be able to see it immediately. Though, if the leak isn’t as severe you may find slow leaking or dribbling out of the sides of the coolant reservoir. This can be met with one of two options, you could simply bring your vehicle to a mechanic to have the coolant reservoir leak fixed through a tank replacement or purchase a coolant leak sealer that when mixed with the active coolant inside of your tank and will begin an internal bonding process to fill in any cracks or gaps.

Consult with a mechanic before inserting any coolant sealer into your revisor to mitigate any accidents or damage.

You Have a Bad Radiator Cap: Radiator Cap Leaking

This solution may be the easiest of the list, but it is also the least likely to resolve your issue. When you have a bad radiator cap you will notice a lack of suction and leaking emitting from the cap itself. If this is how your vehicle’s radiator cap looks then spending the $6 to replace it is a must. Despite that it may not fix the issue, it will make troubleshooting much easier.

Warning: NEVER open the radiator cap directly after turning the car off, as the pressure of the outside air combining with the heat of the coolant may cause it to splash and cause third-degree burns. Wait a couple of hours after parking your vehicle to remove the radiator cap.

Your Radiator Hoses are Loose, Cracked, or Worn out

Unfortunately, the hoses routing from the engine to the radiator can become loose or become brittle over the years. One thing you can try is to park your vehicle overnight over a tarp and see if there are any leaks, then in the morning go underneath the vehicle and feel the hose and the radiator hose clamps around it. If you can tighten the clamps you may be able to stop the leaking, but sometimes tightening the clamps will change nothing. If this is the case the best solution is to bring your vehicle to the mechanic, as replacing the routed wires is not a simple task by any means and takes knowledge and time to replace. If you notice a radiator hose leak you may still be able to drive your car to the mechanic before reaching the dangerously low levels of coolant in the vehicle.

Your Coolant Temperature Sensor Has Gone Bad: Coolant Sensor Replacement

One of the last remaining things you can check is the coolant temp sensor and if it has gone bad. When the low coolant sensor goes bad you could have a perfectly operable tank and no leaks, just a bad sensor or light that will illuminate due to a bad reading. This may seem like a DIY job, but it is actually a very complex repair to tackle. We recommend allowing your mechanic to replace the sensor as it could require removing the coolant tank.

Talk to the Mechanic

If you have gone through all the other steps to checking how to get low coolant light off or after attempting a fix your low coolant light comes on and off intermittently, it may be time to take your vehicle to a mechanic. The last thing you want to happen is the check engine light low coolant temperature light to double up on your dashboard before having it fixed. Our Ultimate® Savers Club may be your answer to an unexpected repair bill.