Mercedes of the S-class W202

1993-2000 of release

Repair and operation of the car

Mercedes W202
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Lubrication system
- 5. Cooling system
   + 5.2. Cooling liquid
   5.3. Antifreeze for a radiator
   5.4. Temperature regulator of cooling liquid (thermostat)
   5.5. Check of the cooling system
   5.6. Hydraulic coupling of the fan
   5.7. Pump of system of liquid cooling
   5.8. Radiator
   5.9. Fan casing
   5.10. Diagnostics of malfunctions of the cooling system
   5.11. Diagnostics of malfunctions of system of indication of level of liquid
   5.12. Engine overheat
+ 6. Heating, ventilation
+ 7. System of ignition
+ 8. Fuel system
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electrical circuitries

5.5. Check of the cooling system


By means of the standard control device it is possible to check leakage of the cooling system and functioning of the safety valve in a carving cover of the cooling system.

Get the control device on a bulk branch pipe of a compensation tank. The manual pump of the device create excessive pressure about 1,4 bars. If pressure falls, find the untight place from where cooling liquid follows, and eliminate a thinness. If pressure falls without signs of an effluence of cooling liquid or even increases, then it is possible to assume loss of cooling liquid in the engine, for example, because of damage of laying of a head of the block of cylinders or a crack to the case.


The safety valve is installed in a radiator cover. Its task – since a certain excessive pressure to open the cooling system and by that to create running off conditions in a compensation tank of excess amount of cooling liquid.

Screw on the control device (1) a carving cover of a radiator (2). Create excessive pressure. The safety valve has to open with a pressure within 1,3-1,4 bars. Otherwise replace a cover.


1. Extend fingers the vacuum valve so that it opened. Check whether the valve at an otpuskaniye is completely closed. The vacuum valve in a cover opens at 0,1 bars of the lowered pressure.
2. Screw a cover on a radiator. At damage replace a rubber sealing ring.


The system of indication of level of cooling liquid generally consists of the sensor in a compensation tank and a control bulb on the dashboard.

Indication of level of cooling liquid at the working engine warns about too low level of cooling liquid and, thanks to it, about a possible overheat of the engine. As soon as ignition joins, the control bulb shines within 30 seconds. At the working engine this bulb at once dies away.

Level of cooling liquid in a compensation tank is removed by means of a float (551). At the low level of cooling liquid in the sensor the contact (550) becomes isolated and the control bulb lights up. Depending on the mode of the movement a control bulb at first it is short-term, and later constantly flashes. If the control bulb flashes, add cooling liquid.


1. Start the engine and leave it to work in the idling mode.
2. Extend the plug on the sensor of level of cooling liquid.
3. Connect an ohmmeter between both contacts on the sensor. At the level of cooling liquid on the mark "max" the measuring device has to show infinity. At an empty compensation tank resistance has to make about 5 Ohms.
4. Stop the engine.
5. If the sensor as it should be though the control bulb does not shine, check electric lines and a control lamp according to the schematic electrical circuitry.


1. If it is required, merge a little cooling liquid.
2. Raise the screw-driver a safety ring (550a).
3. Extend the sensor from a compensation tank.


1. Insert the new sensor with a new sealing ring (552) so that ledges, various on width, on the sensor were recorded in an opening of a compensation tank.
2. Press a safety ring.
3. Fill in cooling liquid.

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