How to check the coolant level in Mercedes Benz?

This blog will answer the following questions: how to check the coolant level in Mercedes Benz? What to do if a check coolant level message appears in the instrument cluster? How to top-up coolant in Mercedes Benz? What are the common problems in the coolant system of Mercedes Benz Cars?

How to check the coolant level in Mercedes Benz?

The coolant level in Mercedes Benz can be checked in the following ways:

• From the instrument cluster
• From the coolant reservoir 

Let’s take a look at the process for both the methods

From the instrument cluster

In Mercedes Benz, the coolant level can be checked from the instrument cluster of the car. Use the multifunction arrow keys on the steering wheel to navigate the service menu in the instrument cluster.

In the service menu, use the down arrows unit to check the coolant level menu is shown. Press the ok button in the middle, the current coolant level will be displayed in the instrument cluster. This is the easiest method to check the coolant level as the driver is away from hot engine parts.

The coolant level can be checked regardless of the operating temperature of the engine. The option to check the coolant level is present in the latest Mercedes Benz models, some of the old models can only display a warning if the coolant level gets too low.

From the coolant reservoir

In order to check the coolant in the coolant system, allow the vehicle to cool down. The operating temperature of the engine must be less than 80 degrees. Slowly unscrew the coolant reservoir cap and check the level of the coolant in the reservoir.

The level of the coolant must be above the ‘T’ mark in the reservoir, all the white plastic areas inside the coolant reservoir must be under the coolant level. Mercedes Benz cars have two coolant reservoirs, the second one is small but the coolant level is checked in the same way.

It is important to park the vehicle on a level surface to get the accurate level of the coolant in the reservoir. When the engine is cold, the level can be up to the T marker bar but if the engine is warm coolant level can be 1.5 cm over the marker.

The engine compartment can be very hot and there is a danger of getting burns when checking the coolant level directly in the reservoir. You can also check the coolant level from the side of the reservoir without opening it. The coolant reservoir must be half filled with blue or red coolant.

What to do if a check coolant level message appears in the instrument cluster?

If a check coolant level message appears in the instrument cluster then perform the following steps.

• Check the coolant temperature gauge in the instrument cluster, if the temperature is too high then turn off the vehicle as soon as possible.
• Allow the vehicle to cool down and open the engine hood.
• Unscrew the coolant reservoir cap slowly and check the coolant level in the reservoir.
• If the coolant level is below the T mark then top up the coolant till the level is up to the T mark.
• Properly screw the cap back on and check if the message is still displayed in the instrument cluster.

If there is no message then it is safe to operate the vehicle but if the message appears again then consult the nearest Mercedes Benz workshop. Additional checks may be required to identify the cause of the coolant leak.

The coolant system is leak tight and the level does not go down unless there is a leak in the system. So if the message is occurring a few days after topping up the coolant, it must be checked by a technician.

How to top-up coolant in Mercedes Benz?

The procedure to top-up coolant in Mercedes Benz is given below:

• Check the color of the coolant, if the color is blue it must be topped up by the same color coolant. It is not recommended to mix blue and red color coolant in the vehicle.
• The coolant concentration in the system is maintained at 50 percent distilled water and 50 percent antifreeze. However, if the vehicle is operated in a hot country then it is possible to keep 90 percent distilled water and only 10 percent antifreeze.
• Once the mixture of coolant and antifreeze is ready, simply unscrew the cap and pour the coolant into the reservoir.
• Start the engine and allow it idle for a few minutes, this ensures there is no air trapped in the coolant system.
• Turn off the engine and check the coolant level again, if it is below the T mark then add more coolant to the reservoir.

What are the common problems in the coolant system in Mercedes Benz cars?

The common problems in the coolant system in Mercedes Benz cars are explained below:

External Leak in the coolant system

If the age and the mileage of the vehicle are high, leaks in the coolant systems are very common. The coolant system uses many hoses to cool down the turbochargers and intercoolers. These hoses get brittle due to the high temperature of the coolant. 

Similarly, the main components of the coolant system like a radiator, thermostat, and water pump can also leak coolant and cause the engine to overheat.

Internal leak in the coolant system

An internal leak from the cylinder head gasket is not common in Mercedes Benz but there are heat exchangers like engine oil cooler or transmission oil cooler. These coolers can leak internally and the oil from the engine can enter the coolant system.

The contaminated coolant cannot cool down the engine and can even damage the coolant level sensor in the reservoir. Similarly, the latest Mercedes Benz engines also use liquid-cooled intercoolers, coolant can leak internally and enter the intake manifold of the engine.

Faulty level sensor

The coolant reservoir has an inbuilt coolant level sensor, the level sensor does not have a float and a potentiometer like the fuel level sensor. It uses two probes in the coolant and when the level goes below the probes, a warning message is displayed in the instrument cluster.

A short or open circuit in the electrical lines of the coolant level sensor can also cause the warning message to appear as the front SAM control unit cannot measure the coolant level in the reservoir.

Conclusion

This blog explained the procedure to check the coolant level in the Mercedes Benz and explained the common fault that can occur in the coolant system. Keeping the correct coolant level and concentration is very important as overheating can lead to expensive repairs.