Turbocharger Failure Analysis & Corrective Procedures

Major causes of turbocharger failure are lack of lubrication and/or oil lag, oil contamination, oil oxidation or breakdown and foreign material in either the exhaust or intake systems.

LACK OF LUBRICATION & OR OIL LAG

Turbocharger failure due to lack of lubrication and/or oil lag occurs when oil pressure and flow is insufficient to lubricate the journal and thrust bearings before the turbocharger is accelerated to high speeds. The turbocharger bearings' need for oil increases as turbocharger speed and engine load increases.

Corrective Procedure

1. During first engine start-up after oil and/or oil filter change, crank engine without starting until oil filter and system are filled and engine oil pressure is obtained, or start and run engine at low idle speed until normal engine oil pressure is obtained.
2. After installation of a turbocharger, note the following:
a. Ensure oil inlet and drain line are clean. If rubber hoses are used, ensure hoses are not hardened or deteriorated. If metal lines are used, ensure lines are not restricted or collapsed.
b. Ensure engine oil is clean and at operating level.
c. Disconnect oil drain line at turbocharger and crank engine without starting until oil flows out of turbocharger center housing. A steady flow of oil indicates that any air pockets have been purged from oil system.

OIL CONTAMINATION

Under certain engine operating conditions the oil bypasses the oil filter, which may allow contaminated oil to enter the turbocharger. Under the following conditions the oil filter may be bypassed: during cold weather when the engine oil is congealed (thickened), when oil filter is restricted, when filter bypass valve is sticking open, when filter element is ruptured, and when filter element is incorrectly installed. Contaminated or dirty oil will wear and fail turbocharger bearings faster than engine bearings due to the high rotational speed of the turbocharger shaft.

Corrective Procedure

Oil and oil filter change periods should never be extended beyond the specified oil and oil filter change intervals.

OIL OXIDATION & OR OIL BREAKDOWN

Primary causes of oil oxidation and/or oil breakdown are engine overheating, piston blow-by, engine coolant leaking into oil system, wrong grade of oil used and lack of proper oil change intervals. Oil oxidation and or oil breakdown will cause sludge accumulation in the oil.
The spinning action of the turbocharger shaft throws the oil against the internal walls of the turbocharger center housing where sludge particles stick and accumulate, affecting oil drainage from the turbine and journal bearings. This will cause turbine seal leakage. The deposited sludge at the turbine end may become hardened due to high turbine temperature, wearing the turbine end journal bearing and bearing bore.

Corrective Procedure

1. When oil leakage at the turbine end of the turbocharger is found, check turbocharger oil drain tube and engine crankcase breathers for restriction. Replace oil drain tube and/or crankcase breathers as required.
2. When an engine oil sludge condition has been found, change oil and oil filter as necessary. Inspect oil drain opening and turbine shaft.

FOREIGN MATERIAL IN EXHAUST OR INTAKE SYSTEMS

Foreign material such as sand, dirt, and dust will damage the turbocharger compressor and turbine wheels due to their high rotational speeds. When servicing the turbocharger, ensure exhaust and intake systems are clean and turbocharger tubing connections are secure.