C9 Urban Transit Bus Engine Caterpillar

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Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

Before you begin inspection of the turbocharger, be sure that the inlet air restriction is within the specifications for your engine. Be sure that the exhaust system restriction is within the specifications for your engine. Refer to Testing and Adjusting, "Air Inlet and Exhaust System - Inspect".

The condition of the turbocharger will have definite effects on engine performance. Use the following inspections and procedures to determine the condition of the turbocharger.

• Inspection of the compressor wheel and the compressor housing

• Inspection of the turbine wheel and the turbine housing

• Inspection of the wastegate

Inspection of the Compressor Wheel and the Compressor Housing

Illustration 1	g00922408
Typical example of a turbocharger (1) Compressor housing (2) Compressor wheel

1. Remove the air cleaner from the compressor inlet.

2. Inspect compressor wheel (2) for damage from a foreign object. If there is damage, determine the source of the foreign object. As required, clean the inlet system and repair the intake system. Replace the turbocharger. If there is no damage, go to Step 3.

3. Clean compressor wheel (2) and compressor housing (1) if you find buildup of foreign material. If there is no buildup of foreign material, go to Step 4.

4. Turn the rotating assembly by hand. While you turn the assembly, push the assembly sideways. The assembly should turn freely. Compressor wheel (2) should not rub compressor housing (1). The turbocharger must be replaced if the compressor wheel rubs the compressor housing. If there is no rubbing or scraping, go to Step 5.

5. Inspect compressor wheel (2) and compressor housing (1) for oil leakage. An oil leak from the compressor wheel may deposit oil in the aftercooler (if equipped). Drain and clean the aftercooler if you find oil in the aftercooler.

   1. Check the oil level in the crankcase. If the oil level is too high, adjust the oil level.

   2. Inspect the air cleaner element for restriction. If restriction is found, correct the problem.

   3. Inspect the engine crankcase breather. Clean the breather or replace the breather if the breather is plugged.

   4. Remove the oil drain tube. Inspect the oil drain hole and the oil drain tube for oil sludge. Inspect the area between the bearings of the rotating assembly shaft. If necessary, clean the rotating assembly shaft, the oil drain hole, and the oil drain tube.

   5. If Steps 5.a through 5.d did not reveal the source of the oil leakage, the turbocharger has internal damage. Replace the turbocharger.

Inspection of the Turbine Wheel and the Turbine Housing

Illustration 2	g00922420
Typical example of a turbocharger (1) Turbine housing (2) Turbine wheel

1. Remove the air piping from the turbine housing.

2. Inspect turbine wheel (2) for damage by a foreign object. If there is damage, determine the source of the foreign object. Replace the turbocharger. If there is no damage, go to Step 3.

3. Clean turbine wheel (2) and turbine housing (1) if you find buildup of carbon or foreign material. If there is no buildup of carbon or foreign material, go to Step 4.

4. Turn the rotating assembly by hand. While you turn the assembly, push the assembly sideways. The assembly should turn freely. Turbine wheel (2) should not rub turbine housing (1). Replace the turbocharger if the turbine wheel rubs the turbine housing. If there is no rubbing or scraping, go to Step 5.

5. Inspect turbine wheel (2) and turbine housing (1) for oil leakage and oil coking. Some oil coking may be cleaned. Heavy oil coking may require replacement of the turbocharger. If the oil is coming from the turbocharger center housing go to Step 5.a. Otherwise go to "Inspection of the Wastegate".

   1. Remove the oil drain tube. Inspect the oil drain hole and the oil drain tube for oil sludge. Inspect the area between the bearings of the rotating assembly shaft. If necessary, clean the rotating assembly shaft, the oil drain hole, and the oil drain tube.

   2. If crankcase pressure is high, or if the oil drain is restricted, pressure in the center housing may be greater than the pressure of turbine housing (1). Oil flow may be forced in the wrong direction and the oil may not drain. Check the crankcase pressure and correct any problems.

   3. If the oil drain tube is damaged, replace the oil drain tube.

   4. Check the routing of the oil drain tube. Eliminate any sharp restrictive bends. Make sure that the oil drain tube is not too close to the engine exhaust manifold.

   5. If Steps 5.a through 5.d did not reveal the source of the oil leakage, the turbocharger has internal damage. Replace the turbocharger.

Inspection of the Wastegate

The wastegate controls the amount of exhaust gas that is allowed to bypass the turbine side of the turbocharger. This valve then controls the rpm of the turbocharger.

When the engine operates in conditions of low boost (lug), a spring presses against a diaphragm in the canister. The actuating rod will move and the wastegate will close. Then, the turbocharger can operate at maximum performance.

When the boost pressure increases against the diaphragm in the canister, the wastegate will open. The rpm of the turbocharger becomes limited. The rpm limitation occurs because a portion of the exhaust gases bypass the turbine wheel of the turbocharger.

The following levels of boost pressure indicate a problem with the wastegate:

• Too high at full load conditions

• Too low at all lug conditions

Note: The housing assembly for the wastegate is preset at the factory and no adjustments can be made.

In order to check the operation of the wastegate valve, verify the correct pressure for the wastegate valve. Remove the line on the wastegate and connect a pressure source to the wastegate. Refer to Specifications, "Turbocharger" for the pressure that is required for the actuating rod to open 1.02 mm (0.040 inch). If the actuating rod does not move by this amount, replace the housing assembly for the turbine of the turbocharger. This housing assembly includes the wastegate valve. If necessary, replace the complete turbocharger.

The boost pressure controls the maximum rpm of the turbocharger, because the boost pressure controls the position of the wastegate. The following factors also affect the maximum rpm of the turbocharger:

• The engine rating

• The horsepower demand on the engine

• The high idle rpm

• The height above sea level for engine operation

• Inlet air restriction

• Exhaust system restriction