Mercedes Benz Check Coolant Level Warning Meaning & Common Causes

Mercedes-Benz vehicles may display check coolant level warnings on the dashboard, which means the engine coolant level is low. Ignoring this warning can lead to engine overheating, failure, and expensive repairs. 

Is your Mercedes-Benz showing a Check Coolant Level warning message on the central display?

Engine coolant, also called antifreeze, is important for engine operation, as a lack of it may result in overheating. 

In this article, we will explain what this warning means and what may cause it. In addition, we will go through what drivers should do when checking coolant level warning comes up. 

What does the Check Coolant Level message mean?

Mercedes engine coolant level low

Check Coolant Level message means that the coolant in the radiator or coolant tank has dropped below the minimum level. This means that the engine may overheat if you continue to drive. 

The water pump pushes the coolant inside the engine, taking away the heat generated by combustion. When the engine coolant level is low, the water pump may not circulate coolant and cool down the engine. 

Coolant goes through several hoses towards the radiator, where it cools down and heads back to the engine to repeat the cooling process. There is also a thermostat, which controls coolant flow to ensure optimum engine running temperatures.

Most systems also have a coolant bottle (overflow reservoir), which acts as a buffer that allows the coolant to expand.

Mercedes-Benz cars have a sensor that monitors the coolant level inside this bottle. If this level drops below a certain level, the car will warn the driver immediately.

How to check the coolant level on a Mercedes Benz?

check Mercedes engine cooling level

Checking the coolant level is quite similar on most Mercedes Benz vehicles, although some differences may be possible. Here is a step-by-step procedure:

  1. Allow the engine to cool down. 
  2. Pull the hood release under the dashboard, driver's side. 
  3. Lift the hood and locate the coolant bottle within the engine bay. This will be a plastic tank with a cap on top of it.
  4. Next, remove the cap from the bottle filler neck by unscrewing it counter-clockwise. Ideally, this should be done only when the engine is cold, ensuring an accurate reading. 
  5. Once the cap is removed, it is possible to see the coolant inside the bottle and check its level. With a cold engine, it should be just at the top of a marker bar inside the filler neck. 
  6. If the engine coolant level is low, add the recommended Mercedes-Benz engine coolant directly to this coolant tank. 

Is it safe to drive a Mercedes-Benz with a coolant level warning on?

can you drive mercedes with coolant level warning on

No. 

When there is not enough coolant inside the cooling system, the coolant (if any) will lose its ability to cool the engine. When an extensive amount of coolant is missing, the engine will overheat within a few minutes.

However, a driver can't know the actual level from the message displayed on the cluster. The only way to determine this is by visually checking the level inside the coolant reservoir.

Check the engine coolant level and add coolant if necessary. If the warning comes up again and the engine starts to overheat, your vehicle may need to be towed to a mechanic. Do not drive the vehicle if it starts to overheat.

Mercedes tow vehicle

If the engine temperature rises when driving, or there is steam coming from under the hood, you must stop immediately, turn off the engine and let the engine cool down.

You may be able to drive as long as the engine doesn't overheat. Monitor the temperature gauge carefully. 

Where did the missing coolant go? 

Mercedes engine coolant level missing

The cooling system is a closed-loop, from which nothing gets out under normal running circumstances.

Possible reasons for the lack of coolant fall into two major categories: external leaks or blown head gasket. This can be anything from cracked hoses or leaking radiators to broken coolant bottles or worn water pumps.

Most of these will cause puddles of liquid under the car unless the leak is minor.

Another possibility is an internal leak such as a blown head gasket, where the coolant gets into those engine components it should not go in. The most common failure that causes this is a broken head gasket, allowing coolant to enter the combustion chamber.

Symptoms that would reveal this condition include white smoke coming from the exhaust and rock-hard coolant hoses.

On newer Mercedes-Benz cars, coolant may also disappear because of cracked oil coolers and EGR coolers on vehicles with diesel engines.

What is the correct engine coolant for Mercedes-Benz

Before filling up, it is important to find out what type of coolant should be used. This is straightforward when buying at the Mercedes dealership, as sales agents know the correct coolant. When this becomes a challenge is when you try to buy a Mercedes-Benz engine coolant from an auto parts store. 

what engine coolant to use on Mercedes benz

Here, drivers may choose between several brands, with most of them being available in several colors. If you are buying coolant from a part store, ask the sales representative to look up the correct coolant for your Mercedes-Benz. 

Mercedes Benz owners should ensure they have a coolant that meets manufacturers' specifications. In most cases, the Mercedes-Benz engine coolant will need to meet MB 625.5 specifications. See the owner's manual. 

In the case of a pre-mixed coolant, filling up comes down to pouring it into the coolant bottle. 

Concentrated coolant (antifreeze) must be mixed with distilled water before usage, usually in a 50/50 ratio.

Why does a Mercedes-Benz lose engine coolant? 

Mercedes looses engine coolant

The most common reasons why a Mercedes-Benz loses engine coolant are: 

  • Coolant reservoir cap not holding pressure
  • Cracked coolant reservoir
  • Cracked, broken, or disconnected coolant hoses
  • Damaged or cracked radiator leaking coolant
  • Blown head gasket

Many Mercedes Benz owners are getting the Check Coolant Level message, although the coolant is correct. Among potential causes for such behavior, a faulty level sensor within the coolant bottle is the most likely one.

Cooling systems’ harsh environment may damage sensitive electronic circuitry inside this sensor, making its readings incorrect. The easiest way of solving the issue is by replacing the sensor, as it is easy to replace and inexpensive.

In addition, damaged wiring and loose or broken connectors are something owners should not rule out.

Conclusion

As we explained, the Check Coolant Level message will warn the driver that the engine is starting to lose coolant and the engine may overheat. 

This doesn’t mean the engine will overheat immediately, although drivers should check the actual coolant level as soon as possible. While filling up with an appropriate coolant can be a solution, owners should track down the cause of the problem.

In most cases, this will be a leak within the cooling system or an engine-related issue in a worse scenario.