3406E Truck Engines Caterpillar

Restriction Of Air Inlet And Exhaust

There will be a reduction in the performance of the engine if there is a restriction in the air inlet system or the exhaust system.

The air flow through a used air cleaner may have a restriction. The air flow through a plugged air cleaner will be restricted to some degree. In either case, the restriction must not be more than the following amount:

• 6.25 kPa (25 inches of H₂O)

Back Pressure is the difference in the pressure between the exhaust and the atmospheric air. The back pressure measurement should be taken in a straight section of pipe. The test location should be a minimum distance of 3 pipe diameters from the turbocharger. The back pressure should not be more than the following amount:

• 10 kPa (40 inches of H₂O)

Measurement Of Pressure In Inlet Manifold

The efficiency of an engine can be checked by making a comparison. Compare 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:

• 99 kPa (29.7 In 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. BE SURE THAT THE AIR INLET OR THE EXHAUST DOES NOT HAVE A RESTRICTION WHEN YOU ARE MAKING A CHECK OF THE PRESSURE.

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

Illustration 1	g00295554
1U-5470 Engine pressure group

Illustration 2	g00298478
Pressure test location (1) Air temperature sensor for the inlet manifold (2) Pipe plug for the air boost (3) Boost pressure sensor

To check the inlet manifold's pressure, remove the pipe plug for the air boost (2). It is not necessary to remove the sensor for the inlet manifold air temperature (1) and the boost pressure sensor (3).

The 1U-5470 Engine Pressure Group can be used to check the pressure in the inlet manifold.

The 1U-5470 Engine Pressure Group has a gauge that indicates pressure inside the inlet manifold. Refer to Special Instructions, SEHS8907 which is included with the engine pressure group for complete instructions. Refer to Operation Manual, NEHS0818, "Using the 198-4240 Pressure Indicator Tool Gp" for the instructions that are needed to use the 198-4240 Pressure Indicator Tool Gp.

Measurement Of Exhaust Temperature

When the engine runs at low idle, the temperature of an exhaust manifold port can indicate the condition of a unit injector.

A low temperature indicates that no fuel is flowing to the cylinder. An inoperative unit injector pump could cause this low temperature.

A very high temperature can indicate that too much fuel is flowing to the cylinder. A malfunctioning unit injector could cause this very high temperature.

Use the 1U-8865 Infrared Thermometer to check this exhaust temperature. You can find operating instructions and maintenance instructions inside the Operator's Manual, NEHS0510, "1U-8865 Infrared Thermometer".

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.

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 total of the air pressure drop of the charged system has exceeded the following value: 13.5 kPa (4 Inches Hg)

If a restriction is discovered, proceed with the following tasks, as required:

• Clean

• Repair

• Replacement

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, remove the air-to-air aftercooler core. Flush the air-to-air aftercooler core internally with a solvent that removes oil and other foreign substances. Shake the aftercooler core assembly in order to remove any trapped debris. Wash the aftercooler core assembly with hot, soapy water. Thoroughly rinse this assembly with clean water, and then blow dry the assembly with compressed air. Blow dry the assembly in the reverse direction of normal air flow. To make sure that the whole system is clean, carefully inspect the system .

Inlet Manifold Pressure

Normal inlet manifold pressure with high exhaust temperature can be caused by blockage in the aftercooler core assembly's fins. Clean the aftercooler core assembly's fins. Refer to "Visual Inspection" for the correct cleaning procedure.

Low inlet manifold pressure and high exhaust manifold temperature can be caused by any of the following conditions:

Plugged air cleaner - Clean the air cleaner, as required. Replace the air cleaner, as required.

Blockage in the air lines - Blockage in the air lines between the air cleaner and the turbocharger must be removed.

Aftercooler core leakage - An aftercooler core leakage should be pressure tested. See "Aftercooler Core Leakage" for the correct procedure to clean parts. Use the same manual for information on repairing parts and on replacing parts.

Leakage of the induction system - Any leakage from the pressure side of the induction system should be repaired.

Inlet manifold leak - An inlet manifold leak can be caused by both loose fittings and loose plugs. Missing fittings, missing plugs, damaged fittings, and damaged plugs can also cause these leaks. Finally, problems with the manifold to cylinder head gaskets can cause this same problem. Check all of these items.

Aftercooler Core Leakage

Illustration 3	g00295702
Using FT1984 Aftercooler Testing Group (1) Regulator and valve assembly (2) Nipple (3) Relief valve (4) Tee (5) Coupler (6) Aftercooler core assembly (7) Dust plug (8) Dust plug (9) Chain

Aftercooler leakage can cause the following conditions to occur:

• Low engine power

• Low boost pressure

• Black smoke

• High exhaust temperature

A large leak in the aftercooler core can be found through a visual inspection. To check for smaller leaks, use the following procedure:

1. Disconnect the air pipes from the inlet side of the aftercooler core assembly and from the outlet side of the aftercooler core assembly.
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   Illustration 4	g00298658
   A typical example of the tooling that is installed is shown above. (1) Coupler (2) Chain (3) Dust plugs

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   Dust plug chains must be installed to the aftercooler core or to the radiator brackets to prevent possible injury while you are testing. Do not stand in front of the dust plugs while you are testing.

2. Install couplers (1) on each side of the aftercooler core. Also, install dust plugs (3).

   These items are included with the FT1984 Air-to-Air Aftercooler Test Group.

   Note: The installation of additional hose clamps on hump hoses is recommended. This additional installation should prevent the hump hoses from bulging while the aftercooler core is being pressurized.

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   NOTICE
   Do not use more than 240 kPa (35 psi) of air pressure or damage to the aftercooler core can be the result.

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   Illustration 5	g00298678
   (5) Regulator and valve assembly

3. Install the regulator and valve assembly (5) onto the outlet side of the aftercooler core assembly. Also, attach the air supply.

4. Open the air valve, and pressurize the aftercooler to 205 kPa (30 psi). Shut off the air supply.

5. Inspect all connection points for air leakage.

6. The aftercooler system's pressure should not drop more than 35 kPa (5 psi) in 15 seconds.

   Note: If the pressure drop is more than the specified amount, use a solution of soap and of water to check all areas for leakage. Look for air bubbles that will identify possible leaks. Replace the aftercooler core, or repair the aftercooler core, as needed.

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   To help prevent personal injury when the tooling is removed, relieve all pressure in the system slowly by using an air regulator and a valve assembly.

7. After you test the aftercooler core assembly, remove the FT1984 Air-to-Air Aftercooler Test Group. Reconnect the air pipes on both sides of the aftercooler core assembly.

Dynamometer Test

In hot ambient temperatures, chassis dynamometer tests for models with an air-to-air aftercooler can add a greater heat load to the jacket water cooling system. Therefore, the jacket water cooling system's temperature must be monitored. Also, monitor the inlet air temperature, which may need a power correction factor. These other measurements may also need a power correction factor:

• Fuel API rating

• Fuel temperature

• Barometric pressure

Note: Refer to Special Instructions, LEBT3477, "Truck Performance And Driveability Diagnostic Guide" and Special Instructions, SEHS8025, "Using The Caterpillar Performance Analysis Report (PAR) Program For On-Highway Truck Engines". The Special Instructions will provide more detailed instructions concerning the preparation of the truck. The publications will also provide more detailed instructions concerning the proper use of the dynamometer.

With dynamometer tests for engines, use the FT1438 Dynamometer Testing Aftercooler. This tool provides an air to a water cooled aftercooler. The tool controls the inlet air temperature to a temperature of 43 °C (109 °F).

Crankcase (Crankshaft Compartment)

Pistons or rings that have damage can be the cause of too much pressure in the crankcase. This condition will cause the engine to run rough. There will be more than the normal amount of fumes rising from the crankcase breather. This crankcase pressure can also cause the element for the crankcase breather to have a restriction in a very short time. This crankcase pressure can also be the cause of any oil leakage at the gaskets and at the seals. These areas would not normally have leakage.

Note: The electronic service tool Cat ET can be used to measure crankcase pressure.

Illustration 6	g00286269
8T-2700 Blowby/Air Flow Indicator

The 8T-2700 Blowby/Air Flow Indicator checks the amount of blowby. See Special Instructions, SEHS8712 for more information on using this tool.

Compression

An engine that runs roughly can have a leak at the valves. An engine that runs roughly can also have valves that need an adjustment. Remove the cylinder head and inspect the valves and valve seats. Removal of the cylinder head is sometimes necessary in order to find small defects. Repairs are normally done when the engine is being reconditioned.

Cylinder Heads

The cylinder heads consist of three main components that can be removed:

• Valve seat inserts

• Valve guides

• Bridge dowels

When any of these components are worn or when these components are damaged, these components can be removed. Refer to Disassembly and Assembly for the replacement of these components.

Valve Lash

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The Electronic Control Module produces high voltage. To prevent personal injury make sure the Electronic Control Module is not powered and do not come in contact with the fuel injector solenoid terminals while the engine is running.

Valve lash is measured between the rocker arm and the valve bridge. All of the clearance measurements and the adjustments must be made with the engine stopped. The valves must be FULLY CLOSED.

Valve Lash Check

An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. Check the valve lash while the engine is stopped. The range is specified in Table 5.

If the measurement is not within this range adjustment is necessary. See Testing And Adjusting, "Valve Lash And Valve Bridge Adjustment".

Valve Lash and Valve Bridge Adjustment

Illustration 7	g00284836
Cylinder and valve location (A) Inlet (B) Exhaust

Illustration 8	g00506544

Adjust the valve lash while the engine is stopped. Use the following procedure in order to adjust the valves:

1. Put the No. 1 piston at the top center position.

   Note: If the engine is equipped with an engine compression brake, loosen the adjusting screw for the slave piston lash prior to adjusting the engine valve lash. Refer to the Testing and Adjusting, "Compression Brake" topic in order to adjust the slave piston lash.

   Note: See Testing and Adjusting, "Finding Top Center Position for No. 1 Piston" for further details.

2. With No. 1 piston at the top center position of the compression stroke, an adjustment can be made to the valves.

   Before any adjustments are made, lightly tap each rocker arm at the top of the adjustment screw. Use a soft mallet to ensure that the lifter roller seats against the camshaft's base circle.

3. Make an adjustment to the valve lash on the inlet valves for cylinders 1, 2, and 4.

   1. Loosen the valve adjustment locknut (3).

   2. Place the appropriate feeler gauge (5) between the inlet rocker arm and the inlet valve bridge. Turn the inlet adjustment screw (4) while the valve adjustment locknut (3) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 6.

   3. After each adjustment, tighten the valve adjustment locknut (3) while the valve adjustment screw (4) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.

4. Make an adjustment to the valve lash on the exhaust valves for cylinders 1, 3, and 5.

   1. Loosen the valve adjustment locknut (1).

   2. Place the appropriate feeler gauge (5) between the exhaust rocker arm and the exhaust valve bridge. Turn the exhaust adjustment screw (2) while the valve adjustment locknut (1) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 6.

   3. After each adjustment, tighten the valve adjustment locknut (1) while the valve adjustment screw (2) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.

5. Remove the top center bolt, and turn the flywheel by 360 degrees in the direction of the engine's rotation. This will position the No. 6 piston at the top center on the compression stroke. Install the top center bolt in the flywheel.

6. Make an adjustment to the valve lash on the inlet valves 3, 5, and 6.

   1. Loosen the valve adjustment locknut (3).

   2. Place the appropriate feeler gauge (5) between the inlet rocker arm and the inlet valve bridge. Turn the inlet adjustment screw (4) while the valve adjustment locknut (3) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 6.

   3. After each adjustment, tighten the valve adjustment locknut (3) while the valve adjustment screw (4) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.

7. Make an adjustment to the valve lash on the exhaust valves 2, 4, and 6.

   1. Loosen the valve adjustment locknut (1).

   2. Place the appropriate feeler gauge (5) between the exhaust rocker arm and the exhaust valve bridge. Turn the exhaust adjustment screw (2) while the valve adjustment locknut (1) is being held from turning. Adjust the valve lash until the correct specification is achieved. Refer to Table 6.

   3. After each adjustment, tighten the valve adjustment locknut (1) while the valve adjustment screw (2) is being held from turning. Tighten to a torque of 30 ± 7 N·m (22 ± 5 lb ft). Recheck each adjustment.

8. Remove the top center bolt from the flywheel after all valve lash adjustments have been made.

   Refer to the Testing and Adjusting, "Compression Brake" topic for information on adjusting the slave piston lash.

Turbocharger

Inspect the condition of the bearing when one of the following events occur:

• Every 483,000 kilometers (300,000 miles) of operation

• Every 6000 hours of operation

• Unusual sounds or vibrations in the turbocharger

A quick check of the bearing condition can be made by disassembling the turbocharger. This can be done by removing the piping from the turbocharger and inspecting the following items.

• The compressor impeller

• The turbine wheel

• The compressor cover

Rotate the compressor and the turbine wheel assembly by hand and observe by feeling excess end play. The rotating assembly should rotate freely. There should be no rubbing or binding of the rotating assembly. Replace the turbocharger with a new turbocharger or a rebuilt turbocharger when any of the following conditions occur:

• The impeller rubs the compressor cover.

• The turbine wheel rubs the turbine housing.

End play is checked with a dial indicator. Attach a dial indicator with the indicator point on the end of the shaft. In order to check the end play, move the shaft in and out.

The turbocharger senses boost pressure. This actuates the wastegate valve. The wastegate valve 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. This moves the actuating rod in order to close the wastegate valve. Then, the turbocharger can operate at maximum performance.

As the boost pressure increases against the diaphragm in the canister, 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

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

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

• The engine rating

• The high idle rpm

• The height above sea level for engine operation