Attention! In order to continue the trip, you can also, especially in summer, top up with clean water. In this case, it is necessary to make adjustments to the composition of the radiator coolant as soon as possible.
6-cylinder or 4-cylinder engine with air conditioning: coolant level, cold engine (coolant temperature approx. +20°С) must reach the interface between the black upper part and the transparent lower part of the expansion tank.
4-cylinder engine without air conditioning: coolant level, cold engine (coolant temperature approx. +20°C) should reach the mark in the radiator filler pipe.
Add coolant if the level is too low.
To avoid engine damage, add coolant when the engine is cold.
Attention! Carefully open the locking cap when the engine is hot. There is a risk of scalding! Lay a cloth over the locking cover when opening. If possible, open the locking cap only if the coolant temperature drops below 90°C.
When opening, first lift the locking cap slightly to relieve excess pressure. After that, turn the cover further and remove it.
Carry out a visual inspection if the coolant level drops in a short time.
Checking antifreeze
The following test tool is required: test hydrometer.
The concentration of antifreeze should be checked regularly before the onset of winter to avoid risks, especially if pure water has been added occasionally.
1. Warm up the vehicle until the upper coolant hose leading to the radiator is warm.
2. Carefully open the sealing cap on the expansion tank.
Attention! Do not open the lock cover when the engine is hot.
3. Take the coolant with a measuring hydrometer and read its density on the float.
In our latitudes, engine frost protection must be guaranteed down to -30°C, in very cold climates down to -45°C.
Adding Coolant Concentrate (Mercedes Benz)
Attention! Since some parts of the cooling system are made of aluminium, only a suitable antifreeze/anticorrosion agent approved by Mercedes-Benz should be used for this purpose.
Example: Frost protection measurement for a 4-cylinder engine (without air conditioning) using a hydrometer guarantees this protection down to -20°C. In this case, drain 1.3 liters of coolant from the cooling system and then add 1.3 liters of pure antifreeze concentrate. This ensures that the engine is protected from freezing down to -37°C. If it is necessary to guarantee the protection of the engine against freezing down to -45°C, change 1.7 liters of fluid.
Measured value,°С | ||||
0 | –10 | –20 | –30 | |
Quantitative difference, l | ||||
Gasoline engines | ||||
4-cyl. -37°/ no air conditioning -45° | 4,0 / 4,4 | 2,4 / 2,8 | 1,3 / 1,7 | 0,5 / 0,9 |
4-cyl. -37°/ ac -45° | 4,5 / 5,0 | 2,7 / 3,2 | 1,4 / 1,9 | 0,5 / 1,0 |
6-cyl. -37°/ -45° | 5,0 / 5,5 | 3,0 / 3,5 | 1,6 / 2,1 | 0,6 / 1,1 |
Diesel engines | ||||
2.0L engine -37°/ -45° | 4,0 / 4,4 | 2,4 / 2,8 | 1,3 / 1,7 | 0,5 / 0,9 |
2.0L engine -37°/ -45°with A/C | 4,5 / 5,0 | 2,7 / 3,2 | 1,4 / 1,9 | 0,5 / 1,0 |
2.2 l engine -37°/ -45° | 3,5 / 3,9 | 2,1 / 2,5 | 1,1 / 1,5 | 0,5 / 0,8 |
2.2 l engine -37°/ -45°with air cond. | 3,8 / 4,1 | 2,3 / 2,6 | 1,2 / 1,6 | 0,5 / 0,8 |
2.5 l engine -37°/ -45° | 3,8 / 4,1 | 2,3 / 2,6 | 1,2 / 1,6 | 0,5 / 0,8 |
Attention! The values given in the table are valid for a coolant temperature of approx. +20°C.
Close the cap on the radiator and check the antifreeze protection again after a test drive.
Checking the tightness of the cooling system
By squeezing and bending, check the coolant hoses for porous spots, replace hoses that have become stiff.
The hoses must not be pushed too short on the connecting pipes.
Check tightness of rubber hose clamps, replace clamps if necessary.
Check the seal on the radiator cap or expansion tank for damage.
Attention! A too low coolant level can also be caused by an incorrectly tightened radiator cap (no tightness).
A clear coolant leak and/or presence of oil in the coolant, as well as white clouds of exhaust gases when the engine is hot, indicate a damaged cylinder head gasket.
Attention! Sometimes it is difficult to locate a leak. In this case, we recommend using a pressure test in a workshop (special device required). It is also possible to check the safety valve of the radiator cap.