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6.3.6. Cooling liquid

Cooling liquid consists of mix of antifreeze and water with addition of additives of corrosion protection. Mercedes fills in a concentrate which chemical composition is developed especially for engines of the company in the cooling system of the engines. Proportions of water and antifreeze depend on total of cooling liquid of the cooling system of each type of the engine. The share of antifreeze has to make 50% – it protects liquid from freezing at a temperature of -37 °C. At the content of antifreeze more than 50% worsen a heat transfer of cooling liquid. If the share of antifreeze is less than 40%, its action, first of all anticorrosive protection worsens, and at a negative temperature cooling liquid begins to get denser. Important: if it is required from cooling liquid, you should not add only the distilled water, also antifreeze and a security measure from corrosion are necessary.
   Sensor of level of cooling liquid
The sensor of level of cooling liquid for petrol engines has the same device, as well as the sensor for diesel engines. All practical advice, works on check of the sensor and its operation are similar described for diesel engines in the section 4 "Diesel Engines".
   Replacement of cooling liquid

"To 120 000 km there are each 4 years"
4-cylinder engine
1. Carefully turn off a cover of a broad tank, lower excessive pressure from the cooling system.

Be careful, at the hot engine it is possible to get burns.

2. Install the heater regulator on dashboards in the provision of the maximum heating.
3. Remove protection of a case from below.

Fig. 5.26. Drain stopper of a radiator: 1 – stopper

4. Substitute reception capacity under a radiator and the engine, on the lower part of a radiator turn off a drain stopper of 1 (fig. 5.26) and merge cooling liquid. Sideways it is possible to put on a short hose (internal diameter of 12 mm) the union to direct liquid to capacity.

Fig. 5.27. Putting on of a hose on the union of the block of cylinders: 1 – hose

5. Put on a hose of 1 (fig. 5.27) with an internal diameter of 14 mm the drain union on the right on the block of the engine and open it.
6. That cooling liquid merged better, uncover a broad tank. Merge cooling liquid and cover reception capacity.
7. After full discharge of cooling liquid wash out a radiator clear water.
8. For the gulf of cooling liquid wrap a cap on the block of cylinders of the engine and a drain stopper of a radiator.
9. Establish protection of a case.

Fig. 5.28. Jellied mouth of a radiator

10. Slowly fill in cooling liquid through a jellied mouth (fig. 5.28), at the same time the level of liquid has to reach a ledge at the bottom of a broad tank (it is visible at an open cover) that corresponds to distance of 5,5 cm to the top edge of a jellied branch pipe.
11. Launch the engine and let's it work on the raised turns about 2 min. Establish a heater on the maximum heating. At the same time constantly add cooling liquid in a broad tank.
12. Wrap a cover of a broad tank.
13. Let's work to the engine before turning on of the fan then stop the engine.
14. Check the level of cooling liquid, if necessary add.
15. Warm up the engine. At the same time air will quit the cooling system through a cover of a broad tank. Double-check the level of cooling liquid. If necessary add a little water.
Features of replacement of cooling liquid of the 6-cylinder engine
1. Turn a two-level cover of a broad tank on 1/2 turns and take off pressure in system. Turn a cover and remove it.

At the 6-cylinder engine the cover has two steps of pressure. As a result after an engine stop pressure in system can grow to 2 bars, and liquid will not follow.

2. Before filling of system turn out temperature sensor on the thermostat case.
3. Fill the cooling system until liquid begins to follow from a thermostat opening.
4. Wrap the sensor of temperature and add liquid to norm.
5. Wrap a cover so that the ledge on a broad tank was recorded.
Features of replacement of cooling liquid of the 8-cylinder engine
6. The engine has a two-level cover of a broad tank.
7. On the block of cylinders of the engine there are two drain valves.

   Check of cooling liquid
Regularly before the onset of cold weather check concentration of antifreeze in cooling liquid, especially if during operation you added water to system.
For check it will be required денсиметр — the device for measurement of density. You can transfer the received value of density to value of temperature of freezing of cooling liquid.

1. Launch the engine and warm up it until the top branch pipe of a supply of cooling liquid to a radiator becomes warm.
2. Carefully open a cover of a broad tank.

There is a danger to get burn.

Fig. 5.29. Check of cooling liquid by means of a densimetr

3. Absorb densimetry cooling liquid and determine density (fig. 5.29) by the provision of a float.

Concentration of antifreeze for our latitudes has to prevent freezing of cooling liquid up to the temperature of -37 °C, for areas with a frigid climate — to –45 °C.

Daimler-Benz allows to use antifreezes only of own production. At the malfunctions which arose because of use of antifreeze of other producers, the guarantee loses force.

4. Add antifreeze to the cooling system in the volume specified in tab. 5.5 to provide necessary value of temperature of freezing at operation of the car in this region.

Table 5.5. Antifreeze concentrate volume for obtaining the required value of temperature of freezing of cooling liquid

Example of use of the table. If antifreeze density on the engine with a working volume of 2,0 l corresponds to temperature of freezing of -10 °C, then to receive temperature of freezing of -37 °C, it is necessary to merge 3,1 l of cooling liquid and to fill in the same quantity of a concentrate of antifreeze in system. For obtaining temperature of freezing of -45 °C it is necessary to replace 3,7 l.
5. Close a cover of a broad tank, make a trial trip, again check concentration of antifreeze.