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
   Check of a compression in engine cylinders
   Check of the engine by means of the vacuum gage
   Belt of the streaming drive of auxiliary units
   + 6-cylinder petrol engines (M104.944 and M104.990/994)
   + 8-cylinder petrol engines (M119.970/981 and M119.971/981)
   + 12-cylinder petrol engines (M120.980/982)
   + 6-cylinder diesel engines (OM603.971)
   + 6-cylinder diesel engines (OM606.961)
+ Cooling systems, heating
+ Power supply system and release
+ Engine electric equipment
+ Gear shifting box
+ Automatic transmission
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment






Check of the engine by means of the vacuum gage

Basic provisions and fluctuations of an arrow of the vacuum gage at diagnostics of malfunctions of the engine

Using the vacuum gage, it is possible to obtain information on a condition of the engine and to define that laying of a head of the block of cylinders is punched, the power supply system is damaged, rings are damaged, the power supply system is incorrectly adjusted, valves, etc. are damaged. Unfortunately, indications of the vacuum gage can be interpreted incorrectly therefore these measurements need to be used in combination with other methods of check of the engine. Both absolute value of indications of the vacuum gage, and speed of their change are important for the correct definition.

 PERFORMANCE ORDER

1. Connect the vacuum gage to the inlet pipeline. Start and warm up the engine up to the normal working temperature.
2. Consider indications of the vacuum gage. If the engine is in the normal state, indications of the vacuum gage have to be 430-560 mm Hg, and the arrow of the vacuum gage has to stand still.


Low constant indications of the vacuum gage demonstrate that laying between the inlet pipeline and the case of a throttle is damaged, the vacuum hose is damaged, the moment of ignition or the wrong installation of phases of gas distribution is incorrectly determined.

If indications of the vacuum gage are lower than norm on 80 - 200 mm Hg and fluctuate, then, perhaps, laying of the inlet pipeline near an entrance opening is damaged or the injector is faulty.

If indications constantly fall on 50 - 100 mm of mercury. rather stable value, perhaps, valves are damaged. In this case it is necessary to measure a compression in engine cylinders.

If indications fall, but is not regular, then, perhaps, gets jammed the valve or there is a failure in ignition.

If indications quickly fluctuate with an amplitude about 100 mm Hg, at constant turns of idling, and from an exhaust pipe there is a smoke, perhaps, the directing plugs of valves are damaged.

If indications quickly fluctuate at increase in turns of idling, then, perhaps, laying of the inlet pipeline or laying of a head of the block of cylinders is damaged, springs of valves are weakened, burned valves or there is a failure in ignition.

Small fluctuations about 25 mm of mercury. are usually connected with failures in system of ignition.

If indications strongly fluctuate, then, perhaps, laying of a head of the block of cylinders or the cylinder is damaged.

If the arrow slowly moves over a wide range of values, then, perhaps, the system of the operated ventilation of a case is littered, laying of the inlet pipeline or laying between the case of a butterfly valve and the pipeline is damaged.

Check, indications of the vacuum gage after sharp and full opening of a butterfly valve and its return to a starting position are how fast restored. If the engine is in the normal state, indications reduce almost to zero, then norms increase about 130 mm Hg above and again decrease to former values at constant turns of idling. If indications are restored slowly and pass through a maximum after closing of a butterfly valve, then, perhaps, piston rings are damaged. If there is a long delay, then, perhaps, the exhaust system is littered.