RACE-THRUST BEARING 1T0686 - Caterpillar

All Turbocharged Caterpillar Engines In Applications With Air-To-Air AftercoolersA failed turbocharger bearing system can result in increased clearances and increased turbocharger shaft orbiting. This can allow engine oil to be pumped through increased clearances and into the air or exhaust systems of the engine. When a failure occurs under loaded engine conditions, turbocharger shaft/wheel breakage may occur. This too can result in oil being pumped into the air or exhaust systems.
DO NOT OPERATE AN ENGINE WITH A FAILED TURBOCHARGER BEARING SYSTEM.Oil in an air inlet or exhaust system is an unstable situation and MUST be avoided. Air-To-Air Aftercooled (ATAAC) engines can "trap" large quantities of oil which can lead to very serious engine damage. Therefore, do NOT operate an engine with a failed bearing system. Always check the air and exhaust systems for retained oil during a turbocharger repair.
A turbocharger that fails a wheel under engine load can produce foreign object debris in the inlet or exhaust air systems. This debris can result in repeated turbocharger/engine failures. Illustration 1 shows a damaged compressor wheel. The damage occurred during heavy engine load (high turbocharger speed) and was the result of heavy thrust bearing wear. Broken compressor blades were lodged in the air filter canister and were (later) found to be responsible for a second failed compressor wheel (see Illustration 2) and foreign object damage to a third compressor wheel (see Illustration 3). The second and third failures could and should have been avoided. Make sure ALL debris is removed from the engine after a turbocharger failure. Thorough inspection and cleaning of the air and exhaust systems should be conducted. The air system includes the path from the air cleaner, through the turbocharger compressor and aftercooler to the inlet valves. The exhaust system includes the path from the exhaust valves through turbocharger turbine tot he vehicle exhaust system. Failure to follow these instructions could result in subsequent and repeated turbocharger failures.
Illustration 1. Turbocharger compressor wheel damaged at high engine load condition.
Illustration 2. Debris left from the first failure caused this second compressor wheel failure.
Illustration 3. Debris left from the first and second failures caused this damage to the third compressor wheel.