Mercedes W124

since 1985-1995 of release

Repair and car operation



W124 Mercedes
+ Governing bodies and control devices
+ MAINTENANCE
+ 2. Maintenance (diesel engines)
+ ENGINE
+ 4. Repair of 6-cylinder petrol SOHC engines
+ 5. Repair of 6-cylinder petrol DOHC engines
+ 6. Repair of the diesel engine established in the car
- 7. Major maintenance of engines
   7.2. General information
   7.3. Recommendations about engine removal
   7.4. Removal and installation of 4-cylinder petrol engines
   7.5. Removal and installation of 6-cylinder petrol engines
   7.6. Removal and installation of diesel engines
   7.7. Sequence of dismantling of the engine
   + 7.8. Analysis of a head of the block of cylinders
   + 7.9. Assembly of a head of the block of cylinders
   7.10. Removal of pistons with rods
   7.11. Removal of a cranked shaft
   7.12. Block of cylinders of the engine
   7.13. Pistons and rods
   7.14. Cranked shaft
   7.15. Survey of radical and shatunny bearings
   7.16. Engine balance of assembly at major maintenance
   7.17. Installation of piston rings
   7.18. Installation of a cranked shaft
   7.19. Check of a working gap of radical bearings
   7.20. Installation of a cranked shaft
   + 7.21. Installation of pistons with rods
   7.22. Engine start after major maintenance
+ COOLING SYSTEM
+ FUEL SYSTEM
+ 10. System of injection of BOSCH CIS-E fuel (KE-JETRONIC)
+ 11. System of injection of BOSCH HFM fuel
+ 12. Fuel system of diesel engines
+ 13. Fuel system of diesel engines
+ SYSTEMS OF START, IGNITION
+ 15. System of ignition of 4-cylinder petrol engines
+ 16. System of ignition of four-cylinder petrol engines
+ PRESTARTING HEATING
+ TRANSMISSION
+ 19. Mechanical transmission
+ 20. Automatic transmission
+ POWER SHAFTS
+ BRAKE SYSTEM
+ SUSPENSION BRACKET
+ BODY
+ ELECTRIC EQUIPMENT
+ CHECK OF MALFUNCTIONS






7.15. Survey of radical and shatunny bearings

GENERAL INFORMATION

Typical defects of bearings

Even thus that radical and shatunny bearings are subject to replacement at major maintenance of the engine, they are necessary for examining carefully as they can give valuable information concerning an engine condition.

Failure of the bearing can occur because of a lack of greasing, presence of dirt or other alien particles, an engine or corrosion overload (see fig. Typical defects of bearings). Irrespective of the reason of failure of the bearing the reason which has caused an exit of the bearing out of operation before the engine should be eliminated will repeatedly gather.

At survey of bearings remove them and spread out in the same order as they were established on the engine. It will allow to define the corresponding neck of a cranked shaft and will facilitate search of malfunctions.

Alien particles can get to the engine various ways. Metal particles can be in engine oil as a result of normal wear of the engine. Small particles together with engine oil can get to bearings and easily take root into a soft material of the bearing. Big particles, getting to the bearing, will scratch the bearing or a neck of a cranked shaft. The best prevention of failure of the bearing for this reason, carefully clear all internal surfaces of the engine and keep them clean at engine assembly. Also frequent and regular replacement of oil with the filter is recommended.

Insufficient greasing of necks of a cranked shaft can be caused by many different reasons, such as high temperature of oil, an overload of the engine and leakage of oil.

The manner of driving by the car also influences durability of the bearing. Completely open butterfly valve at low turns of the engine creates high load of bearings and expression from a zone of contact of an oil film. These loadings lead to emergence of cracks in a working part of the bearing that weakens the bearing and can lead to a separation of an antifrictional layer from a steel basis.

Movement on short distances leads to corrosion of bearings as a result the engine does not leave on the stabilized working temperature at which water vapor and corrosion gases are removed. These pairs and gases, being condensed in engine oil, form acid and a deposit. Acid together with engine oil gets to bearings and corrosion of bearings begins.

The wrong selection of bearings at engine assembly also leads to failure of bearings. The bearings established with a preliminary tightness, leave an insufficient working gap of the bearing therefore decreases or there is no butter layer for greasing.

Bolts of fastening of covers of radical bearings

Measurement of length of a bolt of fastening of a cover of the radical bearing

On 6-cylinder petrol DOHC engines it is necessary to measure length of bolts of fastening of covers of radical bearings. On other engines it is recommended to use new bolts for fastening of covers of radical bearings.

PERFORMANCE ORDER
1. Measure length of each bolt from the head basis till the end of a carving part of a bolt (see fig. Measurement of length of a bolt of fastening of a cover of the radical bearing). If the length at least one bolt exceeds admissible limits, it is necessary to replace all bolts in a set.

Bolts of fastening of covers of shatunny bearings

Place of measurement of the minimum diameter of a bolt of fastening of a cover of the shatunny bearing of the 4-cylinder petrol engine

PERFORMANCE ORDER
1. Measure length of bolts of fastening of covers of shatunny bearings. However at assembly of the engine it is desirable to replace bolts with the new always.
2. Vypressuyte bolts from rods.
3. On 4-cylinder petrol engines measure diameter of a bolt in the narrowest part (see fig. Place of measurement of the minimum diameter of a bolt of fastening of a cover of the shatunny bearing of the 4-cylinder petrol engine). If diameter of a bolt less admissible, replace bolts in a set.
4. On other engines measure length of a bolt from the head basis till the end of a carving part. If the length of a bolt exceeds admissible limits, it is necessary to replace bolts in a set.