The coolant level warning light is on. What's wrong?

What Factors Might Cause the Coolant Light to Come on?

You might be surprised to learn that a “low coolant” light doesn’t necessarily mean that coolant is low; but there could be other issues, including failing parts leading to coolant becoming low over time. Since most modern vehicles, including most BMWs, utilize coolant that’s developed to last a significant amount of time, the low coolant light is concerning.

Low Coolant

Of course, it is highly possible that the illuminated light is indeed correct and that your coolant level is not where it should be. Low coolant is a problem for your car’s cooling system, especially in a performance vehicle like a BMW that requires higher quality conditions to run optimally.

Faulty Sensors

BMWs are basically a complex network of communicating technology. The car’s warning system runs off of a series of sensors for various parts and functions of your vehicle. There are sensors that are specifically purposed to determine the coolant level and the functioning of the cooling system. These sensors can also fail on their own, communicating to the driver that there’s a problem when indeed there isn’t.

Failing Radiator Seal

The radiator circulates the coolant. In order to do this, it must contain the coolant but it also must contain the pressure in the system. It does so by way of airtight seals, which can become damaged or corroded. When the cooling system reaches a low pressure, the car might perceive this as low coolant. In this case, the sensor will likely need to be replaced.

Coolant Leak

Coolant leaks can occur due to a number of reasons, including a broken radiator seal or a compromised radiator. It’s important to have your coolant levels inspected and keep an eye out for leaks beneath your car or throughout your engine to detect leaks in a timely manner—otherwise you might wind up on the side of the road with an overheated engine.


Low Coolant Symptoms

Low coolant symptoms can vary depending on how low your vehicle is on antifreeze. Typically, low coolant will trigger your antifreeze light. Some vehicles might display a "Check Coolant" message on the dashboard. If your coolant light is on, you may notice some of these oddities.

The high-temperature gauge is near or in the red

One tell-tale sign of low coolant is the high-temperature gauge on the dashboard. This gauge is designed to tell you when the engine is getting too hot. Most often, the gauge should stay near the center of the H and C symbols. If the gauge is reading close to the H, shut your engine down and have it towed to a Firestone Complete Auto Care near you for repairs.

The A/C system is malfunctioning

When you use your vehicle’s heat, the coolant helps regulate the flow of hot air into the cabin. If the coolant is low and your air conditioning is running, you may notice hot air coming from your car A/C vents. (Psst! In winter, try these tips to stay warm when your heat isn’t working!)

There’s a sweet-smelling odor

When there’s a coolant leak in your vehicle, you may notice a sweet smell in your air conditioning or under the hood. This is because antifreeze contains glycol, a sweet, viscous liquid used to help regulate the freezing and boiling point of water. While strange odors may be a sign of car issues, they are not always a clear indicator. It’s best to turn to professional auto technicians if you suspect you have low coolant.

Your Coolant Level Sensor is faulty

Sometimes, an illuminated coolant light may be due to a faulty coolant level sensor. If this sensor malfunctions, it could be causing the coolant light to turn on even if you don’t have low antifreeze levels.

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.

Coolant Light Comes on When Car Starts

If the coolant light comes on when you start the car and goes out when you start driving, it usually means that the coolant level is a little low. When the engine coolant is cold, the coolant level sensor triggers the warning light. As the coolant heats up with the engine, it expands raising the level. Check coolant levels when the engine is completely cold and top up if necessary. This is not applicable if the coolant warning light is blue.

How Much Does it Cost to Fix the Coolant Levels Warning Light?

How much it will cost to fix the coolant warning light will depend on the problem. In some cases, a coolant change might be all that you need to fix the problem. However, if you have been driving with the coolant light on, you may have engine damage which can be expensive to repair. Other issues like damage to the sensor, coolant leaks, and damage to the coolant pump will vary in price depending on the exact issue. The best thing to do is book a diagnostics test for your car so that you can find out what has gone wrong and how much you can expect to pay to have it repaired.

How Long can I Drive with Low Coolant?

Whether or not it’s safe to drive with low coolant depends on the circumstances. It would be advisable to pull off the road, switch off the engine and check to see if there’s any coolant remaining in the expansion tank. If there’s coolant in the tank, it’s at or just under the minimum mark and there’s no signs of a leak, you should be good to carry on as normal. Ensure you top up with coolant before your next journey.

If there’s no remaining coolant in the expansion tank, then it’s difficult to assess how much remains in the system and the chances are, with that much loss of coolant, there could be a leak. Under these circumstances, it would not be advisable to continue your journey unless you can top it up.

How can we help?

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