3306C Truck Engine Caterpillar

Measurement Of Pressure In Inlet Manifold

The efficiency of an engine can be checked with a comparison of the pressure in the inlet cover and the information in the Technical Marketing Information (TMI).

This test is used when there is a decrease of horsepower from the engine, yet there is no actual sign of a problem with the engine.

The correct pressure for the inlet manifold is also given in the Technical Marketing Information (TMI), "Fuel Setting and Related Information". These standards are established under the following conditions:

• 96 kPa (28.8 inches) of Hg dry barometric pressure.

• 29°C (84°F) outside air temperature

• 35 API rated fuel

Any change from these conditions can change the pressure in the inlet manifold. The outside air may have a higher temperature and a lower barometric pressure than the values that are given above. This will cause a lower inlet manifold pressure measurement than the pressure in the TMI. Outside air that has both a lower temperature and a higher barometric pressure will cause a higher inlet manifold pressure measurement.

A difference in fuel density will change horsepower (stall speed) and boost. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that appears in the TMI.

If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that appears in the TMI.

Ensure that the air inlet and the exhaust manifold do not have an air restriction when you check the pressure.

Note: The electronic service tool may also be used to check the pressure in the inlet manifold.

Illustration 1	g00295554
1U-5470 Engine Pressure Test Group

To check the inlet cover's pressure, remove one of plugs on the top of the inlet cover. Connect the following items to this opening:

• Adapter

• Seal

• Reducing bushing

• 1U-5470 Engine Pressure Test Group

The 1U-5470 Engine Pressure Test Group has a gauge that indicates pressure inside the inlet cover. Instructions for using this tool group appear in the Special Instructions, SEHS8524.

Air-to-Air Aftercooled Systems

Visual Inspection

Inspect the following components of the air-to-air aftercooler system:

• All lines

• All hoses

• All gasket joints

Make sure that the constant torque hose clamps are tightened to the correct torque. Check the truck manufacturer's specifications for the correct torque.

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Pressurized air can cause personal injury. When pressurized air is used for cleaning, wear a protective face shield, protective clothing, and protective shoes.

Note: Whenever any parts for the air-to-air aftercooler system are replaced, perform a leak test. Also perform a test when one of these parts has been repaired.

Check the welded joints for any cracks. Check the brackets for correct positioning. Also, make sure that these brackets are in good condition. Use compressed air to clean any debris or any dust from the aftercooler core assembly. Inspect the aftercooler core assembly's fins for the following conditions:

• Damage

• Debris

• Salt corrosion

Use a stainless steel brush to remove any corrosion. Make sure that you use soap and water.

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Pressurized air can cause personal injury. When pressurized air is used for cleaning, wear a protective face shield, protective clothing, and protective shoes.

Note: When air-to-air aftercooler parts are repaired and air-to-air aftercooler parts are replaced, a leak test should be completed.

Do not use winter fronts and shutters with aftercooler systems. Winter fronts can only be used on certain truck models. The jacket water pumps on these models will overheat before the air temperature of the inlet manifold becomes excessive. These truck models use special alarms or other indicators. These instruments warn the operator about an engine overheating. Check with the manufacturer about the use of both winter fronts and shutters.

Air System Restriction

Periodically, take pressure measurements at the turbocharger outlet and at the inlet manifold. The air lines and the cooler core must be inspected for internal restriction under both of the following conditions:

• The air flow is at a maximum level.

• The charged system exceeds a total air pressure drop of 13.5 kPa (4 in Hg).

If a restriction is discovered, inspect the cooler core for cleaning, for repairing, and for replacement needs, as required:

Turbocharger Failure

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Pressurized air can cause personal injury. When pressurized air is used for cleaning, wear a protective face shield, protective clothing, and protective shoes.

If a turbocharger failure occurs, follow this procedure:

1. Remove the air-to-air aftercooler core.

2. Flush the air-to-air aftercooler core with a solvent for removing oil and other foreign substances.

3. Shake the aftercooler core. This may allow any trapped debris to escape.

4. Wash the aftercooler core with water that is hot and soapy. Then, thoroughly rinse the aftercooler core with clean water.

5. Blow dry the assembly with compressed air. Blow dry the assembly in a reverse direction of the normal air flow.

6. Take extra care to ensure that the system is clean.