The oil filter is clogged and the bypass valve is open.

A lubrication valve or filter bypass valve malfunctions as a result of worn or binding components.

If enough contaminated oil enters the turbocharger bearings, the bearings will wear out or large particles may plug the internal oil passages and starve the turbocharger of oil.

Because of the extremely high top speeds of the turbine and compressor wheels (up to 100 mph), any large particles that enter through the inlet or exhaust systems can mechanical y damage the rotating parts of the turbocharger. Therefore, proper maintenance of the air cleaner is extremely important. Also, thorough cleaning of the inlet and exhaust systems is essential if there has been a previous turbocharger failure, valve failure, or other failure that could leave foreign particles in the engine.

Removal, Disassembly, and Cleaning

The removal of the turbocharger from the engine is not a complicated task when you follow the procedures in the manufacturer's instructions.

After removing the turbocharger from the engine, you should make sure the exterior of the turbocharger is cleaned of all loose dirt before disassembly to prevent unneccessary scoring of the rotor shaft. Disassemble it according to the manufacturer's maintenance and repair manuals.

The turbocharger parts accumulate hard-glazed carbon deposits, which are difficult to remove with ordinary solvents. This is especially true if the turbine wheel and shaft, diffuser plate, and the nozzle ring and inner heat shield are affected. The cleaner must remove these stubborn deposits without attacking the metal. All parts should be cleaned as follows:

1. Place all parts in a divided wire basket so parts will not be damaged through contact with each other. Do not pile them in the basket. Avoid mutilating precision ground surfaces.

2. Immerse the parts in mineral spirits or similar solvents.

CAUTION

Never use a caustic solution or any type solvent that may attack aluminum or nonferrous alloys.

3. Allow the parts to soak as needed to remove the carbon. A soft bristle brush maybe used, if necessary, to remove heavy deposits. Never use wire or other brushes with stiff bristles.

4. With the oil orifice removed, flush out the oil passages in the main casing from the bearing end to remove dirt loosened by the soaking.

5. Remove the parts from the tank. Drain and steam clean thoroughly to remove all carbon and grease. Apply steam liberally to the oil passages in the main casing.

6. Blow off excess water and dry all parts with filtered compressed air.

7. Carefully place parts in a clean basket to avoid damaging them before inspection and reassembly.

Parts Inspection

Inspect all turbocharger parts carefully before you rinse them. All parts within manufacturer's recommended specifications can be used safely for another service period. Damage to the floating bearing may require replacement of the turbocharger main casing with a new part or an exchange main casing.

Inspect the turbine casing. If you find cracks which are too wide for welding, replace the casing.

Do not use the exhaust casing if it is warped or heavily damaged on the inside surface caused by contact with the turbine wheel or a foreign object, or if it is cracked in any way.

Usually, oil seal plates do not wear excessively during service and can be reused if they have not been scored by a seizure of the piston ring.

As you inspect the diffuser plates, look for contact scoring by the rotor assembly on the back of the diffuser plate or broken vanes. This scoring will make the plate unacceptable for reuse.

Inspect the inner heat shield. If it is distorted, replace it.

Dents found on the outer heat shield can usually be removed, allowing its reuse. However, if this shield is cut or split in the bolt circle area, replace it.