Troubleshooting Engine Vibration{1000, 1151, 1162, 1206} Caterpillar

On-Highway Engine:

C7 (S/N: YPG1-UP; NPH1-UP; KAL1-UP; FMM1-UP; SAP1-UP; C7S1-UP; WAX1-UP; LBM1-UP; FML1-UP)

C9 (S/N: SRB1-UP; 9DG1-UP; ETK1-UP; CKP1-UP; C9S1-UP; MTB1-UP)

C-10 (S/N: MBJ1-UP; 2PN1-UP; 3CS1-UP; 8YS1-UP)

C11 (S/N: KCA1-UP)

C-12 (S/N: 8YF1-UP; MBL1-UP; 9SM1-UP; CPD1-UP; 1YN1-UP; 2KS1-UP; 9NS1-UP; TME1-UP)

C13 (S/N: LEE1-UP; JAM1-UP; KCB1-UP)

C15 (S/N: BXS1-UP; MHP1-UP; NXS1-UP; SDP1-UP; MXS1-UP)

C-15 (S/N: EGH1-UP; MBN1-UP; 6NZ1-UP; 9NZ1-UP)

C-16 (S/N: 7CZ1-UP; W1A1-UP)

C-18 (S/N: MDP1-UP; MEP1-UP; CJP1-UP)

Introduction

Do not perform any procedure in this Special Instruction until you read this information and you understand this information. Refer to Special Instruction, SEHS7914 for any additional information.

This Special Instruction provides a procedure for the diagnosis of the engine related linear vibration problems for On-Highway Engines. The following Special Instruction will provide a method that will tell if the engine complies with Caterpillar's allowable vibration levels. Illustration 3 shows the complete troubleshooting procedure. Vibration complaints arise due to objectionable levels of vibration in the operator's compartment. Vibration problems are usually caused by one of the following:

• Defects in the engine mounting due to misalignment or improper design

• Defects in the cab mounting due to misalignment or improper design

• Misalignment or equipment on the engine is not balanced.

• Chassis resonance with orders of vibration in the engine that are standard

The above defects contribute to vibrations that may appear to the operator to be caused entirely by the engine. The troubleshooting procedure for the engine vibration that follows has been designed to diagnose the true source of the vibration with a minimum unnecessary expenditure of time and material.

A vibration meter that measures the amplitude of displacement and frequency is needed to perform the vibration analysis. 221-2370 Vibration Analyzer Group can be used to perform these tests. For more information, refer to Tool Operating Manual, NEHS0850.

Illustration 1	g01299034
221-2370 Vibration Analyzer Group

Instructions for Completing the Engine Vibration Questionnaire

The engine vibration questionnaire is a way to record the history of engine vibrations. The engine vibration questionnaire is a way to identify vibrations from nonengine components. A dynamic analysis is required when the vibration occurs while the vehicle is in motion. In most cases, the engine is not the cause of the vibration when this situation occurs. Instead, look for the components of the drive train that are out-of-balance or components that have been deformed due to the torque reaction.

Comments about suspected components are listed on the engine vibration questionnaire. If nonengine sources of vibration are discovered, consult the manufacturer of the chassis for assistance.

Illustration 2	g01298844

Flow Chart for Troubleshooting Engine Vibration

Illustration 3	g01298621

Discussion of Troubleshooting Procedure

The complete troubleshooting procedure is outlined in Illustration 3.

(A) Complete the questionnaire to establish the nature of the excessive vibration complaint.

• If the vibration occurs when the vehicle is stationary, proceed to the in-chassis vibration test. Interpretation of the data from the in-chassis test of vibration will provide information about the cause of the vibration and possible corrective action. The only reliable method in order to determine if the engine complies with Caterpillar allowable levels of vibration is to perform an isolated engine vibration test.

• In some circumstances, even if the vibration occurs when the vehicle is moving or the engine is under load, it may be necessary to verify that the engine vibration is within specification. Under these circumstances, proceed to the isolated engine vibration test. Determine if the isolated engine complies with Caterpillar's allowable vibration levels.

(B) Determine if the condition is static or if the condition is dynamic. Follow the proper procedure.

(S1) Perform a speed sweep.

(S2) Visually inspect all brackets and mounts for looseness. Visually inspect all brackets and mounts for seizure. Mounts or brackets that are loose or frozen can cause loss of isolation. Loss of isolation causes a transfer of energy into the chassis. This will cause resonant conditions.

(S3) Performing an evaluation of the clutch can identify a failed clutch. Performing an evaluation of the clutch can identify an unbalanced clutch. A cracked center plate or a cracked disc can cause vibration in static conditions or dynamic conditions.

(S4) Acquire data in order to verify that the clutch is the problem. Repair the clutch.

(S5) Acquire data. Utilize a speed sweep to determine the highest amplitude of complaint. Proceed to acquire data at the engine rpm. Pay special attention to the units of the data points. Refer to Table 1 for On-Highway Truck Engine route points. Refer to Special Instruction, SEHS7914 for details on analysis and tables for data.

Note: If the cab component is the basis of the complaint, obtain data at this point. Determine the amplitude and the frequency.

(S6) Interpret the data. Training is required for analysis of the data to avoid any misinterpretation of the data. Refer to Special Instruction, SEHS7914 for fundamental orders and causes.

• Confirm the complaint of the customer at the location.

• Measure the vibration. Determine the frequency and amplitude at the location with a magnet or a stinger.

• Determine the order of the vibration relative to the the engine's rpm.

• If the engine order can be divided by 1/2, continue to the engine route locations.

• If the amplitude of the frequency of the complaint is within limits, the problem is not the engine.

• If the engine order of the complaint cannot be divided by 1/2, determine if the problem is one of the gear train frequencies. Refer to Table 3.

• If the component of the complaint is in resonance, there will be amplification of the exiting order between the engine and component. Use the analyzer to find the resonant point.

• If the frequency does not correspond to an engine order, it could be driveline related. Possible causes could include the transmission, the drive shaft or the tire. For further assistance, contact the Caterpillar Tier 2 Support staff for Truck Engines.

• If the complaint only happens under loaded conditions, a test while the vehicle is being driven is required. Place the velometer under the seat or on the steering column in order to obtain a route point.

• If the measurement point requires placing the pickup on a small object such as a shift lever, do not restrict movement with the stinger.

• The optional accelerometer is available to determine complaints for frequencies above the eighth order. The complaints are usually associated with a sound. Special routes are required for this sensor.

• If the frequency is related to an engine excitation, determine the method the energy is transmitted to the excited component. The analyzer with the stinger can be used to monitor the motion across piping, mounts, frame and components to determine amplification of the frequency.

(D1) The vibration is a dynamic condition. Duplicate the customer's complaint. The customer's complaint may only occur during operation of the vehicle. This is an important step in order to determine whether the condition is static or dynamic. If the condition is dynamic, contact the OEM and Caterpillar product analyst.

(D2) Contact OEM and Caterpillar. Conditions that have a system resonant are easily resolved with an effort from the OEM and Caterpillar.

(D3) Acquire the data. Determine the dynamic condition with the highest amplitude of the vibration complaint. The complaint can occur with engine speed or vehicle speed.

Note: The condition of the vibration can be vehicle speed dependent as well as engine speed dependent.

(D4) Contact the product analyst for additional information or assistance. Refer to Table 1 for On-Highway Truck Engine cab route points.

(C) Identify the frequency of the vibration. Identify the order of the vibration.

(D) Make necessary repair indicated by Special Instruction, SEHS7914 and Special Instruction, REHS3291.

If an engine fails to comply with Caterpillar's allowable vibration levels in the isolated engine tests, consult the service engineering product analyst for advice on repair.

Terms and Units of Vibration

Refer to Special Instruction, SEHS7914 for details.

Gear Ratios

Illustration 4	g01356155
C15, C-15, C-16 and C-18 (1) Water pump gear (2) Cluster gear (3) Camshaft gear (4) Camshaft idler gear (5) Power steering (6) Accessory idler gear (7) Air compressor (8) Crankshaft gear (9) Oil pump gear

Illustration 5	g01306454
C-10, C11, C-12, and C13 (10) Camshaft gear (11) Water pump gear (12) Camshaft idler gear (13) Accessory Idler gear (14) Air compressor gear (15) Oil pump gear (16) Crankshaft gear (17) Gear for the fuel transfer pump

Illustration 6	g01306512
C7 and C9 (18) Drive gear for the HEUI pump (19) Camshaft (20) Camshaft idler gear (21) Air compressor gear (22) Crankshaft gear (23) Oil pump idler gear (24) Oil pump drive gear

Performing an In-Chassis Vibration Test

A data sheet should be completed for the initial test and for all subsequent tests when modifications have been made. Completing the data sheet will ensure that there is a complete record for all tests for vibration. The initial test is for a vehicle in the as received condition that has objectionable vibration. Additional tests should be performed for each modified condition such as the following conditions:

• Removal of the fan drive belts

• Realignment of the engine mounts

• Disengaging the clutch

Specify each of the test conditions in the space that is provided on the data sheet.

Locations for the Probe

The probe of the vibration should be placed on the engine block as close as possible to the centerline of the crankshaft at the following locations:

• Front horizontal

• Front vertical

• Rear horizontal

• Rear vertical

• Axial

Vertical measurements can be taken from either the top or the bottom of the engine. Horizontal measurements can be taken from either side of the engine. The axial location should be as close as possible to the centerline of the crankshaft. Due to components that are rotating, the measuring point that is normally selected is above the centerline of the crankshaft or below the centerline of the crankshaft. The probe must be positioned against the cast iron cylinder block. The probe may not be placed against the valve covers, tubing, sheet metal, or accessories.

A sixth location of the probe should be selected in the cab on a component that has objectionable vibration or on any component such as the steering wheel, the floor or the doorsill. Specify on the data sheet the location of the probe.

Instructions for Completing the Table for Overall Displacement

Run the engine through the entire idle speed range at 200 rpm intervals. Measure the overall amplitude for displacement for all six locations of the probe at each engine speed. Record the overall amplitude for displacement for all six locations of the probe at each engine speed. It is recommended that a throttle control is used to control the speed of the engine.

Upon completion of Table 4, review the data and check for any discrepancies. If any of the data points are suspected of being in error, repeat the measurements. A good way to check for excessive engine vibration is compare the data with measurements taken on an identical unit that does not have a vibration problem.

Instructions for Completing the Table for Displacement

For each location of the probe in Tables 5 through 8, determine the engine speed that produced the largest displacement. Remeasure the displacement at this engine speed. Measure the displacement for the half, first, second, third and fourth order of vibrations. Refer to Illustration 13. Perform the measurements for the six locations of the probe. The following formula can be used to determine the order of the vibration.

Illustration 7	g01299196

If another order of vibration is found to have significant displacement with the filter, record this displacement and order of vibration in the column marked other.

Interpretation of Data

Refer to Special Instruction, SEHS7914 for details.

Data Sheet for Engine Vibration

Illustration 8	g01299585

Isolated Engine Vibration Test

This test will determine if the engine is within Caterpillar's allowable level. All flywheel driven equipment must be removed. The engine must be suspended or mounted on soft isolator mounts. It is acceptable to suspend the engine with a chain hoist. The engine can be suspended within the chassis, but the clutch, the transmission and the engine mounts must be removed. It is not necessary to disconnect the fuel lines, radiator hoses, wiring or other minor connections.

Illustration 9	g01299828

Allowable Vibration Levels

Illustration 10	g01300488

Beat Frequencies

Complaints caused by beat frequencies can be hard to detect. The beat frequency will not appear in the spectrum plot. Beats are caused by two frequencies very close together that are close in amplitude. Refer to Illustration 12. Beats can be easily seen in the time scope. Illustration 11 is caused by the excitation of the engine first order and the air compressor at 1.14 order. The observed frequency is much lower than what the actual spectrum will show. Time wave for monitoring can be a valuable tool in vibration analysis.

Illustration 11	g01306883

Illustration 12	g01307974

Virtual Print

Illustration 13	g01301746
(1) Data for route point (2) Engine speed (3) Overall reading at selected point (4) Standard orders (5) Frequency units (6) Non-standard orders