Genuine Mercedes-Benz 190E Rod Bearing

Mercedes-Benz 190E Rod Bearing Parts and Q&A

• Connecting Rod Bearing
  111-038-09-10
  Q: What are the key considerations regarding Rod Bearing during engine overhaul on Mercedes-Benz 190E?

  A:

  Although main and big-end bearings are to be changed during engine overhaul, the old bearings could be retained to be subjected to in-service analysis and bearing shell grading measured by the thickness assigned a colour code. Failure may occur due to not being oiled, presence of dirt or foreign objects, overloading of the engine, or due to corrosion and it is likely to arise again unless the root cause is remedied prior to re-assembly. When inspecting bearing shells they must be taken out of place and be spread on a clean surface so that they can be compared with the relevant crankshaft journal without being in touch with the bearing surface to eliminate skratches. During assembly, filters, or machining may allow dirt into the engine or results in bits of the foreign material incorporated into the bearing material, which can be scored or gouged; complete cleaning and frequent swapping of the oil is important to prevent foreign objects. Possible causes of lack of lubrication include, high heat, overloading, oil leakage, obstructed oil passages, resulting to bearing destruction and overheating. Limited driving habits including full throttle low-speed running can also adversely affect wearing life as they produce very high loads that squeeze out oil and can result in fatigue breakdowns. There is short-haul driving that leads to corrosion by the fact that there is not enough heat to evaporate condensed water and corrosive gases, thus creating acid and sludge that destroys bearing material. Through improper installation during the assembly process, not only it may cause oil starvation and breaking due to tight-fitting bearings or stuck-up dirt. You should also take care not to touch the bearing surface during reassembly lest you create a scratch or contaminate it with dirt. To prevent false economy, it is recommended that bearing shells should be replenished when the engine is being overhauled. Although manufacturers do not suggest that the main bearing cap bolts be inspected, tightening up with new bolts is precautionary on the part of the owner. In the case of big-end bearing cap bolts, it is desirable to make measurements to know whether they need to be renewed, and their renewal is highly encouraged when reassembling them. Bolts can be pressed/tapped out of connecting rods and with 4-cylinder petrol engines; diameter of the narrowest section must be checked; under minimum specified diameter must be renewed. With other engines, the distance along the shank between the bottom of the head and the end should also be measured and must not be more than the maximum allowed.