VALVE GP-RELIEF 2555660 - Caterpillar

Reference: Operation and Maintenance Manual that is supplied with the product.Turbocharger life is dependent on oil. Without it, the turbocharger will be damaged even if the oil interruption is brief. Turbocharger bearing problems can be caused by "dry" startups and "hot" shutdowns. For good turbocharger bearing life, follow these helpful hints on starting, stopping and transporting a product with a turbocharged engine.
Startup
During initial engine startup, the opportunity for oil interruption to the turbocharger is most likely to occur. Engine speed and thus boost should be kept low (1100 to 1300 rpm on engines which have rated speeds of 1800 or more rpm) during the starting of the engine. Try to keep engine speed at these levels until oil pressure is evident on a gauge or the EMS/CMS light and warning goes off.
Shutdown
When stopping a turbocharged engine, a five minute cool-down period at low idle should be used. This five minute cool-down period is important to prevent oil "coking" of the center bearing housing.
Oil coking is the residue left in the turbocharger outlet (return) oil line. Coking is caused by the high temperatures trapped in the turbocharger when the engine is shut down "hot". The high temperatures burn the oil in the turbocharger, leaving a residue. Oil coking (residue) creates a restriction in the outlet oil line. Turbocharger return oil restriction is a major cause of bearing failure which can lead to wheel rub and center housing oil seal leaks.
The watercooled center housing helps prevent oil coking by transferring the heat from the turbocharger oil to the water vent lines. It is also important that the water vent lines are maintained as designed. The configuration of the vent lines allows them to stay filled with water at all times, yet does not bypass sufficient water to allow inadequate heater output and low engine temperatures.
Transporting
When transporting products, cover the engine exhaust stack to prevent the turbocharger from rotating. A vacuum is created in the exhaust stack by air passing across the stack opening. The vacuum then causes the turbocharger to rotate. Since very little oil is left in the turbocharger, the turbocharger bearings may be damaged from the lack of lubrication.
Before removing the product from the transport, remove the exhaust stack covering. Damage to the precleaner will result if the product is equipped with an exhaust ejector.