90736A 4 Mercruiser THERMOSTAT HOUSING ASSEMBLY

Failure of turbocharger bearings and seals can cause large quantities of oil to enter the air inlet and exhaust systems. Loss of engine lubricant can result in serious engine damage.Minor leakage of a turbocharger housing under extended low idle operation should not cause problems as long as a turbocharger bearing failure has not occurred.When a turbocharger bearing failure is accompanied by a significant engine performance loss (exhaust smoke or engine rpm up at no load), do not continue engine operation until the turbocharger is repaired or replaced.
An inspection of the turbocharger can minimize unscheduled downtime. An inspection of the turbocharger can also reduce the chance for potential damage to other engine parts.Note: Turbocharger components require precision clearances. The turbocharger cartridge must be balanced due to high rpm. Severe Service Applications can accelerate component wear. Severe Service Applications require more frequent inspections of the cartridge.Removal and Installation
For options regarding the removal, installation, repair, and replacement, consult your Cat dealer. Refer to the Service Manual for this engine for the procedure and specifications.Cleaning and Inspecting
Remove the exhaust outlet piping and remove the air inlet piping from the turbocharger. Visually inspect the piping for the presence of oil. Clean the interior of the pipes to prevent dirt from entering during reassembly.
Turn the compressor wheel and the turbine wheel by hand. The assembly should turn freely. Inspect the compressor wheel and the turbine wheel for contact with the turbocharger housing. There should not be any visible signs of contact between the turbine wheel or compressor wheel and the turbocharger housing. If there is any indication of contact between the rotating turbine wheel or the compressor wheel and the turbocharger housing, the turbocharger must be reconditioned.
Check the compressor wheel for cleanliness. If only the blade side of the wheel is dirty, dirt and/or moisture is passing through the air filtering system. If oil is found only on the back side of the wheel, there is a possibility of a failed turbocharger oil seal.The presence of oil may be the result of extended engine operation at low idle. The presence of oil may also be the result of a restriction of the line for the inlet air (plugged air filters). The presence of oil and plugged air filters causes the turbocharger to slobber.
Inspect the bore of the turbine housing for corrosion.
Clean the turbocharger housing with standard shop solvents and a soft bristle brush.
Fasten the air inlet piping and the exhaust outlet piping to the turbocharger housing.Turbocharger leak inspection
Inspect the turbocharger for leaksCriteria for CAT leaking classification:
Class 1: Wetness around the leak
Class 2: Forms a drop, but the drop does not fall
Class 3: Drops are falling to the ground
Table 1
Inspection Action(1)(2)
Dry No Action
Damp (Class 1) No action
Pooled (Class 2) Manually clean out internal exhaust passages to meet or exceed level 1 requirements for hydrocarbon build-up.
Drip (Class 3) Manually clean all internal and external surfaces to remove all wet hydrocarbon build-up. After cleaning, operate engine per Operation and Maintenance Manual, SEBU9204, Engine Operation found in the Partial Load Operation section to meet or exceed the parameters. Reinspect for leaks after performing aforementioned engine operation.
(1) If the engine was not operated prior to the leak inspection, then perform the action listed in the table.
(2) If the engine was operated prior to the leak inspection, then document the engine operation history and contact the Dealer Solutions Network (DSN).