E30 series BMW 3

since 1983-1994 of release

Repair and car operation

+ 1. Maintenance instruction
+ 2. Maintenance
- 3. Engine
   + 3.1.2. Specifications
   - 3.2. Dismantle and major maintenance of the engine
      3.2.2. Specifications
      3.2.3. Major maintenance – the general instructions
      3.2.4. Compression check in engine cylinders
      3.2.5. Major maintenance – general comments
      3.2.6. Engine diagnostics by means of the vacuum gage
      3.2.7. Major maintenance – alternatives
      3.2.8. Dismantle of the power unit
      3.2.9. Removal and engine installation
      3.2.10. Order of dismantling of the engine
      3.2.11. Dismantling of a head of the block of cylinders
      3.2.12. Cleaning and check of a head of cylinders and details of the klapanny mechanism
      3.2.13. Repair of valves
      3.2.14. Assembly of a head of the block of cylinders
      3.2.15. Removal of pistons and rods
      3.2.16. Crankshaft dismantle
      3.2.17. Intermediate shaft (only M20 engine)
      3.2.18. Cleaning of the block of cylinders
      3.2.19. Check of a condition of the block of cylinders
      3.2.20. Honningovaniye of cylinders
      3.2.21. Check of a condition of pistons and rods
      3.2.22. Check of a condition of the crankshaft
      3.2.23. Check of radical and shatunny bearings
      3.2.24. Engine assembly order
      3.2.25. Installation of piston rings
      3.2.26. Installation of an intermediate shaft
      3.2.27. Installation of the crankshaft and check of gaps in radical bearings
      3.2.28. Installation of a back epiploon
      3.2.29. Installation of rods and pistons, check of gaps in shatunny bearings
      3.2.30. Engine start-up after repair and a running in
   + 3.3. Engine electric equipment
+ 4. Cooling system
+ 5. Heating and ventilation
+ 6. Fuel system
+ 7. Exhaust system
+ 8. Transmissions
+ 9. Coupling
+ 10. Brake system
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
+ 14. Good advice


3.2.21. Check of a condition of pistons and rods



Rings are subject to obligatory replacement irrespective of their condition.

1. Accurately clear pistons of a deposit and carefully remove rings.
2. Carefully remove rings by means of the adaptation.
3. Clear of a deposit of the bottom of pistons, wash out pistons and rods solvent, carefully clean drainage oil openings in piston flutes.

4. Remove a deposit from flutes of piston rings.
5. If traces of considerable wear on the piston are absent and if boring of cylinders is not required, pistons should not be changed. Normal wear is shown in the form of traces of uniform vertical development on a rubbing surface of the piston and in the form of small weakening of landing of the top kompressionny ring. Nevertheless, replacement of piston rings is obligatory.
6. Carefully check existence of cracks on the bottom and a piston skirt, on lugs of a piston finger and on airfields of piston rings. If on a skirt of the piston chips and teases are observed, it indicates a frequent overheat of the engine. In this case careful check of systems of greasing and cooling is required. The burn-out of the bottom of the piston testifies to operation of the engine with the wrong installation of the moment of ignition. The reason of an obgoraniye of the bottom of the piston along the edges as a rule is abnormal combustion (detonation). If the specified defects are found, it is necessary to find their reason and to eliminate. On late models refusal of system of a retsirkulyatsiya can be the reason of such defects.
7. Piston corrosion in the form of small poles (petting) testifies to penetration into the combustion chamber (and also in a crankshaft case) cooling liquid.

8. Measure a gap between a flute and a new ring in 3–4 places on length of a ring. It is necessary to consider that at different rings standard gaps differ. If the gap exceeds the established limit, it is necessary to replace the piston.
9. Check a gap between the piston and the cylinder, having measured internal diameter of the cylinder and diameter of the piston from this cylinder in the corresponding directions. If the gap exceeds the established limit, the block of cylinders is subject to boring, and it is necessary to replace pistons and rings repair.
10. Check a gap between a piston finger and a rod head for what shake the piston and a rod in opposite directions. If люфт notable, repair of this connection in car-care center is necessary.
11. Removal of pistons from rods, and also check of rods and their editing are carried out in car-care center. If the piston rod in a normal state (люфты there are no also all gaps in norm), it it is not necessary to assort knot.

12. Check existence on rods of cracks and other damages. Remove covers of shatunny bearings, get bearings, wipe landing surfaces on a cover and on a rod, check existence of cracks, scratches and задиров. After check collect a rod, having established into place bearings, tighten nuts by hand.