S-class W202 Mercedes

1993-2000 of release

Repair and car operation

W202 Mercedes
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Greasing system
- 5. Cooling system
   + 5.2. Cooling liquid
   5.3. Antifreeze for a radiator
   5.4. A temperature regulator cooling liquids (thermostat)
   5.5. Check of system of cooling
   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 system of cooling
   5.11. Diagnostics of malfunctions of system of indication of level of liquid
   5.12. Engine overheat
+ 6. Heating, ventilation
+ 7. Ignition system
+ 8. Fuel system
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electroschemes

b47c026d b47c026d

5.5. Check of system of cooling


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

Get the control device on a bulk branch pipe of a compensatory tank. The manual pump of the device create superfluous pressure about 1,4 bar. If pressure falls, find not tight place, cooling liquid from where follows, and eliminate a thinness. If pressure falls without signs of an effluence of cooling liquid or even raises, 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 in the case.


The safety valve is established in a radiator cover. Its task – since a certain superfluous pressure to open system of cooling and by that to create running off conditions in a compensatory tank of superfluous amount of cooling liquid.

Screw on the control device (1) carving cover of a radiator (2). Create superfluous pressure. The safety valve should open at pressure within 1,3–1,4 bar. Otherwise replace a cover.


1. Extend fingers the vacuum valve so that it opened. Check, whether the valve is completely closed at an otpuskaniye. 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 compensatory 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 is shone within 30 seconds. At the working engine this bulb dies away at once.

Level of cooling liquid in a compensatory tank acts in film by means of a float (551). At low level of cooling liquid in the sensor contact (550) becomes isolated and the control bulb lights up. Depending on a movement mode 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 an idling mode.
2. Extend the tip on the sensor of level of cooling liquid.
3. Connect an ohmmeter between both contacts on the sensor. At level of cooling liquid on "max" mark the measuring device should show infinity. At an empty compensatory tank resistance should make about 5 Ohm.
4. Stop the engine.
5. If the sensor as it should be though the control bulb is not shone, check according to the basic electroscheme electric lines and a control lamp.


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


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