Troubleshooting Failures of the Exhaust Tube on 3408E and 3412E Engines{1061} Caterpillar

Introduction

Use this Special Instruction to troubleshoot elevated exhaust temperatures that can damage the exhaust system and shorten the life of the exhaust tube after a field repair.

Description of the Problem

Some machines with the 3408E and the 3412E engines have experienced repeat failure of the exhaust tube between the exhaust manifold and turbocharger exhaust housing after a field repair. These failures are due to excessive temperatures in the exhaust system.

Excessive exhaust temperatures will cause damage and/or warping of the exhaust manifold which will result in misalignment during assembly, exhaust leakage and repeat failure of the exhaust tube. Exhaust temperatures must be returned to acceptable levels, and damaged or warped components in the exhaust manifold assembly must be replaced prior to replacing the exhaust tube in order to prevent repeat failure of the exhaust tube.

Normal or Expected Exhaust Temperatures

Note: The values that are listed in the following table pertain to operation at sea level.

Note: Exhaust temperatures may increase 60 °C or 108 °F during operation in higher ambient temperatures and/or during operation in higher altitudes (above 1000 m (3300 ft)).

When exhaust temperatures reach 760 °C (1400 °F) troubleshooting and repair are required to avoid shortened life of the exhaust tube.

Measurement of High Exhaust Temperatures

Note: Measure exhaust temperatures during normal working operation or during a torque converter stall condition at full load with the engine at the proper operating temperature. Set the sample rate to one per second for period of at least 30 minutes.

Note: Reference the engine serial number in the Technical Marketing Information System (TMI) for the proper nominal engine fuel rate and turbocharger boost pressure at rated torque and peak torque.

A typical test could include the following data sampling. Use the AVSpare Electronic Technician (Cat ET) and the 131-5051 DataView Tool Gp to collect the data. Use an exhaust 4C-6268 Probe in the turbocharger Y manifold ports (right bank and left bank) to measure the exhaust temperature. Use a rate of burn 179-0710 Meter Group to measure the engine fuel rate.

Monitor the status of the following conditions on Cat ET:

• Boost pressure

• Engine speed

• Desired engine speed

• Load factor

• Calculated fuel rate

• Max fuel limit

• FRC limit

Monitor the following Dataview channels:

• Fuel flow rate

• Exhaust temperatures

The following illustrations are examples of screens from Cat ET:

• Boost and load factor

• Fuel consumption rate and injection duration

• Desired engine speed and the actual engine speed

• The fuel position and the rated fuel limit

• Engine coolant temperature and fuel temperature

Illustration 1	g01164814
Boost and load factor for Cat ET

Illustration 2	g01164317
Engine fuel consumption rate and injection duration for Cat ET

Illustration 3	g01164492
Desired engine speed and the actual engine speed for Cat ET

Illustration 4	g01164574
The fuel position and the rated fuel limit for Cat ET

Illustration 5	g01164810
Engine coolant temperature and fuel temperature for Cat ET

Illustration 6	g01164575
Left and right exhaust temperatures for Data-View

Illustration 7	g01164771
Boost pressure and fuel pressure for Data-View

Illustration 8	g01164496
Fuel consumption for Data-View

Compare Collected Data to Normal Values

The peak exhaust temperatures can be compared with the expected temperatures that were noted earlier. The fuel flow rate can be compared to the nominal fuel flow rate that is listed in the TMI. The boost pressure can be compared to the values for the boost pressure that are listed in the TMI. The measured boost pressures must be above nominal levels or below nominal levels by more than 14 kPa (2 psi) in order to be considered significant. Significant deviations of the engine performance from the nominal levels (high fuel rate or low boost) can provide helpful indications of the root cause for the high exhaust temperature.

Slight adjustments of the fuel rate may also be necessary in order to compensate for engine speed, the load factor, and the altitude.

To find the Corrected Fuel Rate (FR), divide the Actual FR by the load factor. Next, divide the Target rpm by the Actual rpm. Now, multiply the two answers from the previous two calculations. Compare the "Corrected FR" to "Nominal Fuel Rate" that is given in the TMI, at sea level for a given engine speed.

Some derate of the nominal fuel rate and the turbocharger boost occurs at higher altitudes. The nominal fuel rate should drop by one percent per 1 kPa (0.1450 psi) drop in atmospheric pressure. The derate starts at 84 kPa (12 psi) of atmospheric pressure at 1550 m (5100 ft) of altitude or above 1550 m (5100 ft) of altitude. This is effectively a nine percent drop in the fuel rate per 1000 m (3300 ft) of altitude. The nominal turbocharger boost should also drop approximately eight to nine percent per 1000 m (3300 ft) of altitude versus conditions at sea level. This is dependent on engine speed. Nominal values in the TMI can be adjusted for operating in different altitudes, as needed.

Probable Root Causes

1. Leaks in the exhaust system

2. Excessive restriction in the muffler

3. Low boost pressure from leaks in the inlet manifold

4. Excessive restriction in the air inlet system

5. Damaged parts or warped parts in the exhaust system

6. Injectors with excessive fuel flow

Recommended Repairs

1. Leaks In The Exhaust System

Check for following conditions:

• Failure of the exhaust tube

• Failure of a gasket or a stud in the exhaust manifold

• Loose clamps

• Poor sealing between the exhaust tube and the manifold

The conditions that are listed above can cause the following problems:

• 50 °C to 100 °C or 90 °F to 180 °F increase in temperature

• Low turbocharger boost

Required Action

The source of leakage must be found. Repair the system in order to stop the leakage. This will restore the proper boost and exhaust temperature.

Note: If low boost is detected, remove heat shields (if equipped) and check for leaks in exhaust manifolds. Leaks in the exhaust manifold will not be visible if the heat shields are not removed.

2. Excessive Restriction in the Muffler

Check for following conditions:

• Faulty muffler, loose baffle, or internal failure

• High restriction (Above 27 inches of H²O)

The conditions that are listed above can cause the following problems:

• 25 °C to 50 °C or 45 °F to 90 °F increase in exhaust temperature

• Low boost

Required Action

Repair the muffler and the exhaust system in order to meet the specified standard for exhaust restriction.

3. Low Boost Pressure From Leaks In The Inlet Manifold

Check for a leaking seal or a leaking line connection.

Leaks can cause the following problems:

• 25 °C or 45 °F increase in exhaust temperature

• Low boost

Required Action

The source of leakage must be found. Repair the system in order to stop the leakage. This will restore the proper boost and exhaust temperature.

4. Excessive Restriction In The Air Inlet System

Check for a dirty air filter.

A dirty air filter can cause the following problems:

• High restriction (Above 30 inches of H²O per 1W-0613 Air Filter Service Indicator or 8N-2694 Indicator )

• 50 °C to 130 °C or 90 °F to 234 °F increase in temperature

Required Action

Replace the air filter in order to maintain the proper airflow through the inlet system.

5. Damaged Parts Or Warped Parts In The Exhaust System

Check for following conditions:

• Parts that have been exposed to excessive heat

• Y manifold that is warped

• Exhaust manifold that is warped

The conditions that are listed above can cause misalignment. This can make the parts difficult to assemble and lead to continued leakage which will result in repeated failure of the exhaust tube.

Required Action

Replace warped parts or damaged parts in order to ensure proper alignment of the exhaust tube. Distortion of the exhaust manifold due to excessive exhaust temperatures has been found on some returned manifolds. The exhaust port may be bowed away from the engine by as much as 6 mm (0.24 inch).

Note: Do not use excessive force to fit new exhaust tubes or other parts. If any tube or part does not align properly, check exhaust manifolds and/or Y manifolds for deformation. Failure to correct warped components or damaged components will preload newly installed components. This can make the parts difficult to assemble and lead to continued leakage which will result in repeated failure of the exhaust tube.

6. Injectors With Excessive Fuel Flow

Check for following conditions:

• Incorrect FLS/FTS setting

• Worn parts or faulty parts in the injectors

The conditions that are listed above can cause the following problems:

• 25 °C to 50 °C or 45 °F to 90 °F increase in exhaust temperature

• High turbocharger boost

• Excessive fuel rates up to 10 percent might also be found.

Required Action

Use the FLS/FTS settings that are listed in the TMI. Troubleshoot the injectors in order to restore the engine to the nominal fuel flow rate. Worn injectors can cause overfueling which can cause excessive exhaust temperatures.

Note: Use only the published FLS/FTS settings that are found in the TMI. Alteration of factory FLS/FTS settings will cause excessive exhaust temperature and repeat failure of components.

Note: Some machines are equipped with a "Variable HP" feature. When the engine is on the dynamometer, ensure that Cat ET is set to the "Proper HP Mode". On the dynamometer, the "default" mode of operation for Cat ET is the "Low HP Mode". When the FLS/FTS are adjusted according to the specifications in the TMI and the engine HP is low, ensure that Cat ET is in the proper "HP Mode". Correlate the power with the correct "HP Mode". Setting the FLS/FTS with Cat ET in the wrong "HP Mode" will result in excessive exhaust temperature and repeat failure of components.

Example

630E Series II Wheel Tractor-Scrapers have "Variable HP" of 475 HP and 518 HP. On the dynamometer, the "default" mode of operation for Cat ET is the "Low HP Mode". When the engine is on the dynamometer in the "Low HP Mode", the engine will show only 475 HP. Dealers and/or customers that are not aware of this may attempt to adjust the FLS/FTS settings in order to achieve 518 HP in the "Low HP Mode". This will result in excessive exhaust temperatures when the engine is in operation with incorrectly set FLS/FTS settings.

Note: In addition to the root causes that are listed above, deterioration of the turbocharger can cause low boost and 50 °C or 90 °F or more increase in exhaust temperature.

References

Troubleshooting References

• Troubleshooting, SENR1037-01, "P-304: Low Power/Poor Or No Response To Throttle"

• Troubleshooting, SENR1037-01, "P-306: Intermittent Low Power Or Power Cutout"

• Troubleshooting, SENR1037-01, "P-310: Excessive Black Smoke"

• Troubleshooting, SENR1037-01, "P-332: Exhaust Temperature Is Too High"

• Troubleshooting, SENR1038-00, "P-304: Low Power/Poor Or No Response To Throttle"

• Troubleshooting, SENR1038-00, "P-306: Intermittent Low Power Or Power Cutout"

• Troubleshooting, SENR1038-00, "P-310: Excessive Black Smoke"

• Troubleshooting, SENR1038-00, "P-332: Exhaust Temperature Is Too High"

• Troubleshooting, SENR1054-04, "Low Power/Poor or No Response to Throttle"

• Troubleshooting, SENR1054-04, "Intermittent Low Power Or Power Cutout"

• Troubleshooting, SENR1054-04, "Excessive Black Smoke"

• Troubleshooting, SENR1054-04, "Exhaust Temperature is Too High"

• Troubleshooting, SENR1060-02, "P-304: Low Power/Poor Or No Response To Throttle"

• Troubleshooting, SENR1060-02, "P-306: Intermittent Low Power Or Power Cutout"

• Troubleshooting, SENR1060-02, "P-310: Excessive Black Smoke"

• Troubleshooting, SENR1060-02, "P-332: Exhaust Temperature Is Too High"

Testing and Adjusting References

• Testing and Adjusting, SENR1018-00, "Measurement Of Pressure In Inlet Manifold"

• Testing and Adjusting, SENR1018-00, "Restriction Of Air Inlet And Exhaust"

• Testing and Adjusting, SENR6476-01, "Measurement Of Pressure In Inlet Manifold"

• Testing and Adjusting, SENR6476-01, "Restriction Of Air Inlet And Exhaust"