C7 On-highway Engines Caterpillar

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Disconnect batteries before performance of any service work.

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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.

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Personal injury can result from rotating and moving parts. Stay clear of all rotating and moving parts. Never attempt adjustments while the machine is moving or the engine is running unless otherwise specified. The machine must be parked on a level surface and the engine stopped.

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 Systems Operation/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 and the Compressor Housing

• Inspection of the Turbine Wheel and the Turbine Housing

• Inspection of the Wastegate

Inspection of the Compressor and the Compressor Housing

Remove air piping from the compressor inlet.

1. Inspect the compressor wheel 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.

2. Clean the compressor wheel and clean the compressor housing if you find buildup of foreign material. If there is no buildup of foreign material, go to Step 3.

3. Turn the rotating assembly by hand. While you turn the assembly, push the assembly sideways . The assembly should turn freely. The compressor wheel should not rub the compressor housing. Replace the turbocharger if the compressor wheel rubs the compressor wheel housing. If there is no rubbing or scraping, go to Step 4.

4. Inspect the compressor and the compressor wheel housing for oil leakage. An oil leak from the compressor may deposit oil in the aftercooler. 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 engine crankcase breather or replace the engine crankcase breather if the engine crankcase breather is plugged.

   4. Remove the turbocharger oil drain line. Inspect the drain opening. Inspect the oil drain line. Inspect the area between the bearings of the rotating assembly shaft. Look for oil sludge. Inspect the oil drain hole for oil sludge. Inspect the oil drain line for oil sludge in the drain line. If necessary, clean the rotating assembly shaft. If necessary, clean the oil drain hole. If necessary, clean the oil drain line.

   5. If Steps 4.a through 4.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

Remove the air piping from the turbine outlet casing.

1. Inspect the turbine 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 2.

2. Inspect the turbine wheel for buildup of carbon and other foreign material. Inspect the turbine housing for buildup of carbon and foreign material. Clean the turbine wheel and clean the turbine housing if you find buildup of carbon or foreign material. If there is no buildup of carbon or foreign material, go to Step 3.

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

4. Inspect the turbine and the turbine wheel housing for oil leakage. Inspect the turbine and the turbine wheel housing for 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 4.a. Otherwise go to “Inspection of the Wastegate”.

   1. Remove the turbocharger oil drain line. Inspect the drain opening. Inspect the area between the bearings of the rotating assembly shaft. Look for oil sludge. Inspect the oil drain hole for oil sludge. Inspect the oil drain line for oil sludge. If necessary, clean the rotating assembly shaft. If necessary, clean the drain opening. If necessary, clean the drain line.

   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 the turbine housing. 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 line is damaged, replace the oil drain line.

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

   5. If Steps 4.a through 4.d did not reveal the source of the oil leakage, the turbocharger has internal damage. Replace the turbocharger.

Inspection of the Wastegate

The turbocharger senses boost pressure which actuates the wastegate valve. The wastegate valve controls the amount of exhaust gas that is allowed to bypass the turbine side of the turbocharger. Regulating the amount of exhaust gas that enters the turbocharger regulates the rpm of the turbocharger.

Illustration 1	g00942619
Typical example (1) Actuating rod (2) Canister (3) Line

When the engine operates in conditions of low boost (lug), a spring presses against a diaphragm in canister (2). This moves actuating rod (1) in order to close the wastegate valve. Then, the turbocharger can operate at maximum performance.

As the boost pressure increases against the diaphragm in canister (2), the wastegate valve opens. The rpm of the turbocharger becomes limited. This 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 valve:

• Too high at full load conditions

• Too low at all lug conditions

Refer to the Technical Marketing Information (TMI) for the actual boost pressure for your engine.

To check the operation of the wastegate valve, verify the correct pressure for the wastegate valve. Refer to Table 1 for the correct pressure.

Remove the air line, and slowly apply the corresponding amount of pressure to the canister. DO NOT EXCEED 200 kPa (29 psi).

When the external supply of air that is connected to line (3) reaches the corresponding pressure for the wastegate valve, the actuating lever should move by 0.50 ± 0.25 mm (0.020 ± 0.010 inch). If the actuating lever does NOT move by this amount, replace the turbine's housing assembly of the turbocharger. This housing assembly includes the wastegate valve. If necessary, replace the complete turbocharger.

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

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:

• Engine rating

• Horsepower demand on the engine

• High idle rpm

• Height above sea level for engine operation

• Inlet air restriction

• Exhaust system restriction