Mercedes S-Class W-140

1991-1999 of release

Repair and operation of the car



Mercedes S-Class
+ Mercedes-Benz cars of the class S (W-140)
+ Operation manual
+ Routine maintenance
+ Engine
- Cooling systems, heating
   Specifications
   + Engine cooling system
   + Systems of ventilation, heating and air conditioning
+ Power supply system and release
+ Engine electric equipment
+ Gear shifting box
+ Automatic transmission
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment






Cooling systems, heating

General information

Engine cooling system

All models of the cars considered in the present manual are equipped with the engine cooling system working with an excessive pressure with thermostatic management of circulation of working liquid. The water pump is fixed on the block of the engine and provides pumping of cooling liquid through a cooling path of the last. The stream of liquid washes regions of an arrangement of each of cylinders in the block then goes to a back part of the engine. The cooling channels laid in casting of the block and a head of cylinders provide intensive cooling of inlet and final ports, areas of installation of spark plugs and the directing plugs of final valves.

General scheme of functioning of the cooling system


1 — the Broad tank
2 — the Cover
3 — the Built-in silikogelevy tank
4 — the Intaking branch pipe
5 — the Radiator
6 — the Thermostat
7 — the Ventilating tube
8 — the Stream from the engine to a radiator
9 — the Stream from a radiator to the engine
10 — the cooling system Pump

11 — the Oil heater
12 — the Block of cylinders
13 — the Head of the block of cylinders
14 — the Forcing heater pipeline
15 — the Heater of windscreen washers
16 — a heater Radiator
17 — the Valve of a double pulsation
18 — the Circulation pulser
19 — the Returnable tube of a heater


Since engine launch the cooling system passes through three modes of functioning: at the first stage until temperature of cooling liquid rose above a certain value, it circulates on a small circle from a working contour of which the radiator is excluded. In process of further warming up of liquid the dish-shaped valve of the voskozapolnenny thermostat entering the highway of system opens and the radiator is connected to a contour of circulation. Further, on reaching temperature of cooling liquid of the next control value, the thermosensitive sensor switch providing activation of the fan of the cooling system, forced which the additional air stream considerably increases efficiency of functioning of the heat exchanger of a radiator works.

The cooling system has a tight design and is densely closed by the cover of a radiator capable to maintain a certain excessive pressure that provides increase in a boiling point of cooling liquid and, respectively, efficiency of the heat sink through a radiator. At excess by internal pressure in system of some certain value, there is an overflowing of excess of cooling liquid on a connecting (overflow) tube in a broad tank. In process of cooling of system liquid automatically comes back from a tank to a radiator.

Dolivaniye of cooling liquid in system is made through a mouth of a broad tank (see the Head Routine maintenance) which at the same time acts also as the receiver accumulating in itself the excess of liquid which is forced out from a radiator.

In view of the listed features of a design, such cooling system received the name closed as in it any functional losses of a working body are excluded.

System of heating and ventilation

The system of heating consists of the fans and heat exchangers located in blocks of forward and back parts of salon. Hot cooling liquid passes through heat exchangers. When moving the handle of management of the modes of a heater located on the control panel (for more details see Comfort of the Head the Operation manual) valves open and hot air begins to come to interior of the car. If to turn on the heater fan, air will move in salon forcibly.

External air before getting to salon, passes through the filter (address the Head Routine maintenance). The main share of particles of dust will settle in the filter. It is necessary to observe frequency of replacement of the filter. The filter blocked by dust will limit air supply in salon that will lead to an air stagnation in salon.

Distribution of streams of air of system of ventilation is carried out by means of gates. The air circulation mode is provided. Gates are operated with the help of servo-drivers.

Independent heater

The independent heater providing a possibility of autonomous warming up of the engine and interior of the car on a signal of the timer or from the DU panel can be included in the regular package of separate models. The principle of functioning of an independent heater is considered in the Section the Independent heater of the Head the Operation manual.