Engine Connecting Rod Bearing Failure

Sometimes a fairly new engine can have fatigued connecting rods if it is a rebuilt engine and the mechanic used cheap parts or the wrong parts for the engine.

Engine connecting rod bearing failure.

The following are typical assembly errors most often made in the installation of engine bearings. 2 4 correct reversed position of offset connecting rod reversed bearing caps in wrong or. Fatigue cracks may also form in the affected area. Possible causes of connecting rod distortion followed by edge wear.

Connecting rod end clearance fillets at end of crankpin should not bind on ends of rod bearing 004 10mm to 010 25mm clearance recommended. In the latter case a connecting rod or bearings may be loosely installed resulting in excess clearance noise and damage. Engine bearings will not function properly if they are installed incorrectly. Tight or stiff bearing problems can be the result of many factors that lead to their malfunction.

Another common cause of rod failure is a bearing seizure. Either way the engine is going to need a new rod. Excessive idling can result in an oil film that can not support the load needed. Rod knock which is a stabilized hammering increasing linearly with rpm occurs when excess clearances as a result of bearing wear cause the rod big ends to beat against the crankshaft at the bottom and top of the piston stroke.

Such a failure may or may not be the rod s fault. If the oil film between the rod bearing and crank journal goes away for any reason even for an instant it can overheat and seize the bearing. Rod bearings receive enormous loads of stress and rank high on the list of catastrophic engine failure. Most car drivers have known about rod knock symptoms if not detected it themselves.

Engine lugging can distort the crankcase and or crankshaft affecting the connecting rod and or main bearings. Rod bearings can spin freeze stretch deform and suffer out of round conditions. In many cases misassembly will result in premature failure of the bearing. Bearing spread main bearings 005 13mm to 020 50mm in excess of crankcase bore diameter connecting rod bearings 020 50mm in excess of rod bore finish of rod bores.

One symptom of engine bearing failure is noise in the engine. Distorted bent or twisted connecting rod is one of the causes of localized loading of engine bearings resulting in excessive wear of the bearing surface along the bearing edge. Rod bearings have precision. Pin failure the pin that connects the connecting rod to the piston called the piston pin wrist pin or gudgeon pin gets a lot of wear.

Fig 5 edge wear due to distorted connecting rod. Clearances and component geometry retard ignition or use fuel with higher octane number. If a bearing isn t set into place securely lubrication will be insufficient and cause failure.