Technical Service Bulletin IB14-J-002A — 2017 ISUZU N-SERIES

AN INVESTIGATION OF RETURNED TURBOCHARGERS HAS IDENTIFIED A COMMON OCCURRENCE OF TURBOCHARGERS BEING REPLACED DUE TO INTERNAL OIL LEAKS WHEN, IN FACT, THERE IS NO OIL LEAK IN OR OTHER FAULT WITH THE TURBOCHARGER. THE PERCEIVED OIL LEAK ACTUALLY MAY BE A NORMAL CHARACTERISTIC OF THE CLOSED POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM OR SOME OTHER UNIDENTIFIED CONDITION. THE PURPOSE OF THE CLOSED PCV SYSTEM IS TO KEEP HARMFUL BLOWBY GAS FROM ENTERING THE ATMOSPHERE. UNFORTUNATELY, BLOWBY GAS PRODUCTION AND AIR INTAKE DEMANDS DO NOT ALWAYS MATCH WHICH ALLOWS SOME OIL VAPOR FROM THE CRANKCASE TO ENTER THE INTAKE SYSTEM. AS A RESULT, THIS CONDITION MAY LEAD TO AN INCORRECT DIAGNOSIS. OIL IN THE INTAKE SYSTEM IS COMMON FOR A CLOSED PCV SYSTEM AND IS NOT A GOOD INDICATOR OF A TURBOCHARGER FAILURE. THE OIL SEAL INSIDE THE ISUZU TURBOCHARGER IS A DYNAMIC SEAL (NOT A RUBBER SEAL). AIR PRESSURE (I.E. BOOST PRESSURE) ON THE COMPRESSOR SIDE AND EXHAUST PRESSURE ON THE TURBINE SIDE KEEP THE LUBRICATING OIL INSIDE THE TURBOCHARGER CENTER HOUSING. A REDUCTION IN PRESSURE ON EITHER SIDE OF THE CENTER HOUSING WILL ALLOW OIL TO PASS INTO EITHER THE INTAKE OR THE EXHAUST SIDE OF THE TURBOCHARGER. IN ORDER TO STOP OIL FROM BYPASSING, THE SOURCE OF THE PRESSURE REDUCTION MUST BE LOCATED AND CORRECTED. THE MOST COMMON CAUSES OF THIS CONDITION ARE A RESTRICTED AIR FILTER, INCORRECT ENGINE OIL, LOOSE INTAKE HOSE CLAMPS, AND/OR EXCESSIVE CRANKCASE PRESSURE. IN ORDER TO BETTER SERVICE THE CUSTOMER AND HELP PREVENT THE UNNECESSARY REPLACEMENT OF UNDAMAGED TURBOCHARGERS, WE ARE PROVIDING THE FOLLOWING INSPECTION INFORMATION DESIGNED TO AID THE TECHNICIAN IN PROPERLY DIAGNOSING TURBOCHARGER CONCERNS.