Component Tests and General Diagnostics
INTRODUCTIONThe main causes of turbocharger failure are oil contamination or breakdown (coking), insufficient lubrication, and ingestion of foreign objects.
Engine oil must be properly maintained to prevent these problems. Avoid oil starvation and excessive turbo heat build up. Use proper caution when performing service and repairs on intake and exhaust systems.
Correctly analyzing turbocharger failure and installing the replacement with proper precautions helps prevent a costly comeback. It is also important to advise the vehicle owner when changes in his or her driving and/or maintenance habits are in order.
FAILURE ANALYSIS
Oil Contamination or Breakdown
Oil contamination or breakdown causes scored bearings and shaft journals and deposit build up in oil passages and seals. These conditions result in oil blow-by, reduced heat dissipation, and insufficient lubrication. This type of damage can be verified by looking into oil inlet and outlet of center housing when turbocharger is removed. Look for oil sludge and carbon build up (coking).
Oil contamination and breakdown can be prevented by:
1. Using oil recommended by the manufacturer for turbo applications.
2. Changing oil and filter according to recommended interval.
3. Proper hot engine shut-down procedure. Idling a short time before turning the engine off reduces peak temperature stagnant oil is exposed to after shut-down.
4. Removing and cleaning oil feed and return lines when installing a replacement turbocharger.
Insufficient Lubrication
Insufficient lubrication will cause bearing failure, resulting in turbine or compressor wheel rub, seal damage, and possible shaft breakage. This type of damage is verified by visual inspection through ends of wheel housing. This failure can occur in combination with oil contamination or breakdown.
Insufficient lubrication can be prevented by:
1. Preventing oil contamination and breakdown.
2. Proper engine cold start procedure. Idle for 30 - 60 seconds before driving away.
3. Proper hot engine shut-down procedure. Switching the engine off at high rpm may drop oil pressure and starve bearings while turbo is still spinning at high rpm. Idle engine a short time before turning off.
4. Priming replacement turbocharger at installation.
Foreign Object Ingestion
Foreign object ingestion will damage turbine and compressor wheel blades. The resulting imbalance will damage bearings and seals. This type of damage is verified by visual inspection of wheels through ends of housing. Look for rolled, broken, or eroded blades.
Foreign object ingestion can be prevented by:
1. Never running engine without a proper air filter.
2. Taking care when changing air filter; prevent debris from entering intake system.
3. Taking care that dirt and foreign objects do not enter intake pipes, turbocharger, or exhaust manifold when these components are removed for repair work. Clean hose connections and clamps before disassembly.
4. Making sure system upstream from turbocharger is clean and free of foreign objects when replacing a unit which had foreign object damage.
PRECAUTIONS WHEN INSTALLING REPLACEMENT TURBOCHARGER
1. Remove and thoroughly clean oil feed and return lines.
2. Check for foreign objects in intake and exhaust systems.
3. Carefully align components and properly torque fasteners.
4. Prime bearings with clean engine oil through oil feed hole on turbo housing.
5. Change engine oil and filter.
6. Disconnect coil and crank engine for 20 seconds. Connect coil, start engine, and idle for 30 - 60 seconds before driving.
ADVICE TO OWNER
1. Read and follow instructions in owner manual.
2. Allow engine to idle 30 - 60 seconds after starting and avoid high rpm until operating temperature is reached.
3. Let engine idle 20 - 30 seconds before shut-down (60 seconds if stopping immediately after hard driving).
4. Change oil and filter at least as often as manufacturer recommendation. Only use oil specified by the petroleum manufacturer for turbo applications.