BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

+ 1. Maintenance instruction
+ 2. Maintenance
- 3. Engine
   + 3.1.2. Specifications
   - 3.2. Dismantle and capital repairs of the engine
      3.2.2. Specifications
      3.2.3. Capital repairs – the general instructions
      3.2.4. Check of a compression in engine cylinders
      3.2.5. Capital repairs – general comments
      3.2.6. Diagnostics of the engine by means of the vacuum gage
      3.2.7. Capital repairs – alternatives
      3.2.8. Dismantle of the power unit
      3.2.9. Removal and installation of the engine
      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 valvate 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. Dismantle of the crankshaft
      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 conrod 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 conrod bearings
      3.2.30. Launch of the engine 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. Useful tips


3.2.21. Check of a condition of pistons and rods



Rings are subject to obligatory replacement irrespective of their state.

1. Accurately clear pistons of a deposit and carefully remove rings.
2. Carefully remove rings by means of 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, then pistons should not be changed. Normal wear is shown in the form of traces of uniform vertical development on the rubbing surface of the piston and in the form of small weakening of landing of the top compression ring. Nevertheless, replacement of piston rings is obligatory.
6. Carefully check existence of cracks on the bottom and a skirt of the piston, on lugs of a piston finger and on airfields of piston rings. If on a skirt of the piston chips and teases are observed, then it indicates a frequent overheat of the engine. In this case careful check of lubrication systems and cooling is required. The burn-out of the bottom of the piston demonstrates operation of the engine with the wrong installation of the moment of ignition. At the edges as a rule abnormal combustion (detonation) is the reason of an obgoraniye of the bottom of the piston. If the specified defects are found, then it is necessary to find their reason and to eliminate. On late models failure of the system of recirculation can be the cause of such defects.
7. Corrosion of the piston in the form of small poles (pitting) of demonstrates 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 ring length. It is necessary to consider that at different rings standard gaps differ. If the gap exceeds the set limit, then the piston should be replaced.
9. Check a gap between the piston and the cylinder, having measured the internal diameter of the cylinder and diameter of the piston from this cylinder in the corresponding directions. If the gap exceeds the set limit, then the block of cylinders is subject to boring, and pistons and rings should be replaced repair.
10. Check a gap between a piston finger and a head of a rod for what shake the piston and a rod in opposite directions. If the side play notable, then is necessary repair of this connection in car service.
11. Removal of pistons from rods, and also check of rods and their editing are carried out in car service. If knot the piston rod in the normal state (side plays are absent and all gaps are normal), then it should not be sorted.

12. Check existence on rods of cracks and other damages. Uncover conrod bearings, get bearings, wipe landing surfaces on a cover and on a rod, check existence of cracks, scratches and zadir. After check collect a rod, having installed into place bearings, tighten nuts by hand.