BMW 7_aya the E38 series from 1994 to 2002
1. Introduction
2. Governing bodies and methods of operation
3. Settings and routine maintenance of the car
4. Engine
4.1. General information and preparatory operations
4.2. Check of compression pressure
4.3. Check of the engine by means of the vacuum gage
4.4. Petrol M60/1 and M60/2 engines
4.5. M62 engine
4.6. Diesel M57 engine
4.7. Diesel M67 engine
5. Cooling systems of the engine, heating, ventilation and air conditioning
6. A power supply system and production of the fulfilled gases
7. Systems of electric equipment of the engine
8. Manual box of gear shifting and coupling
9. Automatic transmission
10. Cardan and power shafts, reducer, differential and stupichny assemblies
11. Brake system
12. Suspension bracket and steering
13. Body
14. Onboard electric equipment
15. Schemes of electric equipment

Четыре значение числа


4.2. Check of compression pressure

Check of compression pressure will require the help of the assistant.


  1. The measurement of compression pressure allows to make general idea about current state of such internal components of the engine as laying of a head of cylinders, elements of the valvate mechanism, pistons and piston rings. The analysis of results of check allows to define whether the engine needs capital recovery repairs, or it is enough to replace only sealing laying of a head of cylinders. Measurement is performed by means of a kompressometr.
  2. Warm up the engine up to the normal working temperature (about the 80th hail.) also muffle it.
  3. Make sure of completeness of a charge of the rechargeable battery.
  4. On petrol models separate sockets of an electrical wiring of coils of ignition.
  5. On the M52 engine remove the ECM relay; on other petrol engines remove the relay or a safety lock of the fuel pump, let's the engine work to full expenditure of the fuel which remained in lines then turn out candles.
  6. On petrol engines turn out spark plugs, and on diesel – glow plugs.
  7. On diesel models depending on type of the engine perform the following operations:
    • M51: Remove the main ECM relay.
    • M57: Separate sockets of an electrical wiring of nozzles and open all soaking-up channels for what remove the available covers, laying, etc.
    • M67: Separate the socket of an electrical wiring of the sensor of position of the camshaft (CMP).
  8. Screw an adapter nozzle of a kompressometr in an opening of a spark plug or a glow plug.

For measurement of a compression of diesel engines it is necessary to make sure that компрессометр has the sufficient range of measurements.

  1. Completely squeeze out the accelerator pedal and, turning the engine a starter, consider and write down indications of a kompressometr when they are stabilized.

Time of carrying out measurement has to be as it is possible well.

  1. Repeat the procedures described in paragraphs 8 and 9 for the remained engine cylinders.
  2. Compare results of measurement by requirements of Specifications.
  3. The compression grows in the serviceable engine very quickly. The low value shown after the first cycle, increasing with the subsequent cycles indicates wear of piston rings. The low value after the first cycle which is not increasing after the following indicates existence of leaks via valves, or the punched laying of a head of the cylinder (also the crack in a head can be the cause). Can lead existence of a deposit on plates to decrease in a compression of valves.
  4. The results received at measurement of a compression have to be approximately identical to all cylinders. If pressure is in any cylinder at the level of minimum admissible and even below, then for clarification of the reason pour in the cylinder through a candle opening in a teaspoon of motive oil and repeat measurement.
  5. If oil addition temporarily improved a compression, most likely, wear of the piston, rings or the cylinder is the reason of its decrease. If increase in a compression did not happen, then it is possible to assume that the reason – in leakage of valves or the punched laying of a head of the block.
  6. The low compression in two next cylinders almost for certain is a consequence of breakdown of laying of a head. Availability of cooling liquid in combustion chambers or in a case of the engine will confirm this assumption.
  7. If the compression in one of cylinders differs from the others more, to us on 1 atm, besides turns of idling are unstable, then the reason, perhaps, excessive wear of a cam of the camshaft.
  8. After conducting check disconnect компрессометр with a nozzle, install the being removed components and connect an electrical wiring.

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4.1. General information and preparatory operations
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4.3. Check of the engine by means of the vacuum gage