bmw 4 series

BMW Coolant Level Low Warning [How to Fix]

Owning a Bimmer comes with a lot of perks, like sheer driving pleasure, sportiness, and a touch of tech and luxury.

However, over the years, working as a mechanic has taught me that owning a BMW also comes with its share of quirks.

One of these is the coolant level warning light on your Idrive infotainment system.

In this article, I am going to explain what this warning means, the main causes, and how to fix and reset this fault.

Let’s get into it!

What Does Coolant Level Low Warning Mean on a BMW?

Now, in order to understand what this message really means, it’s important to first know what coolant is(not everyone does).

In simple, coolant, also known as Antifreeze, is a liquid that circulates through your engine and acts as a coolant and a lubricant.

The purpose of this fluid is to lower the temperature of both the engine and its parts and prevent corrosion.

Your BMW has a special type of sensor (Coolant Level Sensor), which is meant to measure the amount of coolant in your car.

And when it detects a low level, it will send this warning message to inform you about the situation.

So, in simple terms, the low coolant level warning coming up on your BMW’s Idrive screen simply means the vehicle detected that the coolant level is low and needs to be filled up.

BMW Low Coolant Level Alert Causes

Now that you have a better understanding of what the low coolant level warning message means,

let’s take a look at some of the most common causes that may be responsible for triggering this alert from my experience.

There are three possible reasons for the low coolant level alert on a BMW:

1. Low Coolant Level Due to Normal Usage

Over time, as you drive your BMW, the engine operates at high temperatures,

and the coolant naturally depletes over time as it circulates through the engine to regulate the temperatures

That is why BMW recommends that you check your coolant level every 6 months.

2. There is a Leak in your BMW’s Cooling System

The second cause for this low coolant warning light, especially if the antifreeze runs out faster than normal, is a leak in the cooling system.

There are a lot of places where coolant can leak on a BMW, however, from working on BMWs for a long time, I have found the following are the most common places where you can find a leak:

Cracked Coolant Reservoir:

The plastic coolant reservoir mounted in the engine bay is prone to cracking over time.

Inspect your reservoir carefully for any hairline cracks or thicker fissures. Even small cracks can allow coolant to leak out.

Faulty Pipe Connection under the Intake Manifold:

In many BMWs, especially the 3 series, there is a plastic pipe connection under the intake manifold that connects the rubber water hose to the head.

This plastic pipe is hidden from view but is prone to cracking and failure over time. The result is a major coolant leak that quickly drains the system.

This connection is known to be a common issue and can result in coolant leakage if it fails.

Thermostat Housing Crack:

The thermostat housing is another common leak area you should check on your Beamer.

The thermostat housing is a critical component of your BMW’s cooling system.

It’s where the thermostat resides and helps regulate the system’s coolant flow.

Over many heat cycles, the plastic housing can develop cracks that result in leaks.

Leaky Radiator:

The radiator on your BMW plays a crucial role in keeping your engine from overheating by dissipating the heat from the coolant.

Over time, these components may develop cracks or holes that allow coolant to leak out.

Of course, this list is not exhaustive there are other places where your German machine can leak, like the water pump, radiator hoses, and other coolant pipes.

3. Malfunctioning Coolant Level Sensor

The final common cause of the “engine coolant level too low. Top up the coolant at the earliest opportunity” message is a faulty coolant level sensor.

As I mentioned earlier, the coolant level sensor is responsible for monitoring the amount of liquid in your engine.

This sensor is located under your coolant tank and can fail after some time due to moisture, debris, and heat.

If this sensor fails it will send false readings to your BMW’s ECM, and it will believe that the coolant level is low, even when there is plenty of coolant in the system.

The easiest way to determine if a sensor is malfunctioning is by checking your coolant level. The sensor is likely damaged if the level is between the minimum and maximum, but you still receive a warning.

How to Fix and Reset the Low Coolant Level Alert on a BMW

Now that I have explained the leading causes of this problem let us now look at how you can fix it.

I recommend you do the following steps:

Step 1: Top Up the Coolant

Check the coolant level top off if it is below the minimum mark, and drive a bit. Then switch off the engine, disconnect and reconnect the battery terminal to reset the system.

The “Coolant Level Too Low” warning should disappear. If not, then go to step two.

Step 2: Replace the Coolant Level Sensor

If the coolant level is fine then chances are the sensor is the main culprit of this problem.

I personally recommend changing the whole water bottle since it comes with a new sensor.

This should fix the problem.

Step 3: Pressure Test to Find Leaks

If the above steps do not fix the problem and the antifreeze runs out faster than normal,

then it is possible that there are leaks in your cooling system.

You will need to get a pressure test done to easily spot where the leaks are,

I advise taking your BMW to a qualified independent auto technician like me or simply taking it to the nearest BMW Dealership.

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