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


3.2.23. Check of radical and conrod bearings


Types of wear of radical and conrod bearings

A. Scratches because of dirt hit
B. Insufficient lubricant
C. Wrong installation of bearings
D. Wear because of conicity of a neck
E. Formation of a facet on an edge of the bearing
F. Fatigue wear

Radical and conrod bearings at capital repairs of the engine are subject to obligatory replacement, however the bearings which were in operation should be checked carefully to restore the general condition of the engine at the time of repair.

Insufficient lubricant because of the wrong assembly, pollution and penetration of foreign particles, frequent overloads of the engine, corrosion, etc. are causes of destruction of bearings of a bent shaft. Irrespective of the reason which caused destruction of bearings it should be eliminated.

When checking a condition of bearings they should be got from the block of cylinders, covers of radical bearings of a bent shaft, conrod covers and rods. Lay out inserts on a pure surface in the same order in which they were established on the engine.

Dirt and foreign particles get to the engine for various reasons – in the course of assembly, via filters or system of ventilation of a case. Pollution can also get to oil, and from it – to bearings. Often at pollution there are metal particles from machining of details of the engine, or owing to wear at normal operation of the engine. Sometimes at pollution there are remains of abrasive materials after carrying out pritirochny and grinding works, especially at insufficient washing and a clearing of the engine after their termination. Irrespective of the origin reason foreign pollution usually take root into soft alloy of the bearing and are easily distinguishable. Large particles will not be able to take root into the bearing and lead to emergence of scratches and zadir on surfaces as bearing and necks of the crankshaft.

Insufficient lubricant of the engine ("oil starvation") can be caused by a number of the interconnected reasons. An engine overheat (causes oil fluidifying), overloads concern to them (cause expression of oil from the surface of bearings) and pressure decrease because of leak (emission) of oil (because of the raised gaps in bearings, wear of the oil pump, big frequency of rotation of a bent shaft).

Durability of bearings of a bent shaft also significantly depends on skills of driving. Bearings experience the raised strain at the movement with completely open butterfly valve, or with a small speed on an overgear (in the heavy modes of the engine). At the raised loadings there is an expression of an oil film. Bearings experience flexural deformations at which microcracks (fatigue wear) are formed. As a rule there is a bearing covering separation from a steel basis in the form of small particles. Trips on small distances can be the reason of corrosion wear of bearings as because of insufficient warming up the condensed moisture and gases causing corrosion do not manage to be removed.

The wrong installation of bearings at assembly also results in their premature wear. If the gap in bearings is less than norm, then their lubricant is complicated that results in wear as well as owing to "oil to starvation". The dirt or small particles which got under a bearing insert lead to a local raising of an insert and to the increased wear in this part.