Noise, Vibration & Harshness Ford Crown Victoria II

Noise, Vibration and Harshness (NVH)

Noise is any undesirable sound, usually unpleasant in nature. Vibration is any motion, shaking or trembling, that can be felt or seen when an object moves back and forth or up and down. Harshness is a ride quality issue where the vehicle's response to the road transmits sharply to the customer. Harshness normally describes a firmer than usual response from the suspension system. Noise, vibration and harshness (NVH) is a term used to describe these conditions, which result in varying degrees of dissatisfaction. Although, a certain level of NVH caused by road and environmental conditions is normal. This article is designed to aid in the diagnosis, testing and repair of NVH concerns.

Acceptable Noise, Vibration and Harshness

All internal combustion engines and drivelines produce some noise and vibration; operating in a real world environment adds noise that is not subject to control. Vibration isolators, mufflers and dampers reduce these to acceptable levels. A driver who is unfamiliar with a vehicle can think that some sounds are abnormal when actually the sounds are normal for the vehicle type. For example, Traction-Lok(R) differentials produce a slight noise on slow turns after extended highway driving. This is acceptable and has no detrimental effect on the locking axle function. As a technician, it is very important to be familiar with vehicle features and know how they relate to NVH concerns and their diagnosis. For example, if the vehicle has automatic overdrive, it is important to test drive the vehicle both in and out of OVERDRIVE mode.

Diagnostic Theory

The shortest route to an accurate diagnosis results from

1. System knowledge, including comparison with a known good system.
2. System history, including repair history and usage patterns.
3. Condition history, especially any relationship to repairs or sudden change.
4. Knowledge of possible sources.
5. Using a systematic diagnostic method that divides the system into related areas.

The diagnosis and correction of noise, vibration and harshness concerns requires

1. A road or system test to determine the exact nature of the concern.
2. An analysis of the possible causes.
3. Testing to verify the cause.
4. Repairing any concerns found.
5. A road test or system test to make sure the concern has been corrected or brought back to within an acceptable range.

Glossary of Terms

Acceleration - Light

An increase in speed at less than 1/2 throttle.

Acceleration - Medium

An increase in speed at 1/2 to nearly full throttle, such as 0-97 km/h (0-60 mph) in approximately 30 seconds.

Acceleration - Heavy

An increase in speed at 1/2 to full throttle, such as 0-97 km/h (0-60 mph) in approximately 20 seconds.

Ambient Temperature

The surrounding or prevailing temperature.

Amplitude

The quantity or amount of energy produced by a vibrating component (G force). An extreme vibration has a high amplitude. A mild vibration has a low amplitude.

Backlash

Gear teeth clearance.

Boom

Low frequency or low pitched noise often accompanied by a vibration. Also refer to Drumming.

Bound Up

An overstressed isolation (rubber) mount that transmits vibration/noise instead of absorbing it.

Brakes Applied

When the service brakes are applied with enough force to hold the vehicle against movement with the transmission in gear.

Buffet/Buffeting

Strong noise fluctuations (less than 1000 Hz) caused by gusting winds. An example would be wind gusts against the side glass.

Buzz

A low-pitched sound (200-5000 Hz) like that from a bee. Often a metallic or hard plastic humming sound. Also describes a high frequency (200-800 Hz) vibration. Vibration feels similar to an electric razor.

Camber

The angle of the wheel in relation to the true vertical as measured looking from the front of the vehicle. Camber is positive when the wheel angle is offset so that the top of the wheel is positioned away from the vehicle.

Scheme 1

Caster

The angle of the steering knuckle in relation to the true vertical as measured looking from the side of the vehicle.

Scheme 2

Chatter

A pronounced series of rapidly repeating rattling or clicking sounds.

Chirp

A short-duration high-pitched noise associated with a slipping drive belt.

Chuckle

A repetitious low-pitched sound. A loud chuckle is usually described as a knock.

Click

A sharp, brief, non-resonant sound, similar to actuating a ball point pen.

Clonk

A hydraulic knocking sound. Sound occurs with air pockets in a hydraulic system. Also described as hammering.

Clunk/Driveline Clunk

A heavy or dull, short-duration, low-frequency sound. Occurs mostly on a vehicle that is accelerating or decelerating abruptly. Also described as a thunk.

Coast/Deceleration

Releasing the accelerator pedal at cruise, allowing the engine to reduce vehicle speed without applying the brakes.

Coast/Neutral Coast

Placing the transmission range selector in NEUTRAL (N) or depressing the clutch pedal while at cruise.

Constant Velocity (CV) Joint

A joint used to absorb vibrations caused by driving power being transmitted at an angle.

Controlled Rear Suspension Height

The height at which a designated vehicle element must be when driveline angle measurements are made.

Coupling Shaft

The shaft between the transfer case and the front drive axle or, in a 2-piece rear driveshaft, the front section.

CPS

Cycles per second. Same as hertz (Hz).

Cracks

A mid-frequency sound, related to squeak. Sound varies with temperature conditions.

Creak

A metallic squeak.

Cruise

Constant speed on level ground; neither accelerating nor decelerating.

Cycle

The process of a vibrating component going through a complete range of motion and returning to the starting point.

Decibel

A unit of measurement, referring to sound pressure level, abbreviated dB.

Drive Engine Run-Up (DERU) Test

The operation of the engine through the normal RPM range with the vehicle standing still, the brakes applied and the transmission engaged. This test is used for noise and vibration checks.

Driveline Angles

The differences of alignment between the transmission output shaft, the driveshaft and the rear axle pinion centerline.

Scheme 3

Driveshaft

The shaft that transmits power to the rear axle input shaft (pinion shaft). In a 2-piece driveshaft, it is the rearmost shaft.

Drivetrain

All power transmitting components from the engine to the wheels; includes the clutch or torque converter, the transmission, the transfer case, the driveshaft and the front or rear drive axle.

Drivetrain Damper

A weight attached to the engine, the transmission, the transfer case or the axle. It is tuned by weight and placement to absorb vibration.

Drone

A low frequency (100-200 Hz) steady sound, like a freezer compressor. Also described as a moan.

Drumming

A cycling, low-frequency (20-100 Hz), rhythmic noise often accompanied by a sensation of pressure on the ear drums. Also described as a low rumble, boom or rolling thunder.

Dynamic Balance

The equal distribution of weight on each side of the centerline, so that when the wheel and tire assembly spins, there is no tendency for the assembly to move from side-to-side (wobble). Dynamically unbalanced wheel and tire assemblies can cause wheel shimmy.

Engine Imbalance

A condition in which an engine's center mass is not concentric to the rotation center, causing excessive motion.

Engine Misfire

When combustion in one or more cylinders does not occur or occurs at the wrong time.

Engine Shake

An exaggerated engine movement or vibration that directly increases in frequency as the engine speed increases. It is caused by non-equal distribution of mass in the rotating or reciprocating components.

Flexible Coupling

A flexible joint.

Float

A drive mode on the dividing line between cruise and coast where the throttle setting matches the engine speed with the road speed.

Flutter

Mid to high (100-2000 Hz) intermittent sound due to air flow. Similar to a flag flapping in the wind.

Frequency

The rate at which a cycle occurs within a given time.

Gravelly Feel

A grinding or growl in a component, similar to the feel experienced when driving on gravel.

Grind

An abrasive sound, similar to using a grinding wheel, or rubbing sand paper against wood.

Hiss

Steady high frequency (200-800 Hz) noise. Vacuum leak sound.

Hoot

A steady low frequency tone (50-500 Hz), sounds like blowing over a long neck bottle.

Howl

A mid-range frequency (200-800 Hz) noise between drumming and whine. Also described as a hum.

Hum

Mid-frequency (200-800 Hz) steady sound, like a small fan motor. Also described as a howl.

Hz

Hertz; a frequency measured in cycles per second.

Imbalance

Out of balance; heavier on one side than the other. In a rotating component, imbalance often causes vibration.

Inboard

Toward the centerline of the vehicle.

Intensity

The physical quality of sound that relates to the strength of the vibration (measured in decibels). The higher the sound's amplitude, the higher the intensity and vice versa.

Isolate

To separate the influence of one component to another.

Knock

A heavy, loud, repetitious sound, like a knock on the door.

Moan

A constant, low-frequency (100-200 Hz) tone. Also described as a hum.

Neutral Engine Run-Up (NERU) Test

The operation of the engine through the normal RPM range with the vehicle standing still and the transmission disengaged. This test is used to identify engine related vibrations.

Neutralize/Normalize

To return to an unstressed position. Used to describe mounts. Refer to Bound Up.

Outboard

Away from the centerline of the vehicle.

Ping

A short duration, high-frequency sound, which has a slight echo.

Pinion Shaft

The input shaft in a driving axle that is usually a part of the smaller driving or input hypoid gear of a ring and pinion gearset.

Pitch

The physical quality of sound that relates to its frequency. Pitch increases as frequency increases and vice versa.

Pumping Feel

A slow, pulsing movement.

Radial/Lateral

Radial is in the plane of rotation; lateral is at 90 degrees to the plane of rotation.

Scheme 4

Rattle

A random and momentary or short duration noise.

Ring Gear

The large, circular, driven gear in a ring and pinion gearset.

Road Test

The operation of the vehicle under conditions intended to produce the concern under investigation.

Roughness

A medium-frequency vibration. A slightly higher frequency (20 to 50 Hz) than a shake. This type of vibration is usually related to drivetrain components.

Runout

Lateral runout means measuring the movement or "wobble" of a wheel or tire at the sidewall. Radial runout means measuring the out-of-round at the tread surface.

Rustling

Intermittent sound of varying frequency (100-2000 Hz), sounds similar to shuffling through leaves.

Shake

A low-frequency vibration (5-20 Hz), usually with visible component movement. Usually relates to tires, wheels, brake drums or brake discs if it is vehicle speed sensitive, or engine if it is engine speed sensitive. Also referred to as a shimmy or wobble.

Shimmy

An abnormal vibration or wobbling, felt as a side-to-side motion of the steering wheel in the driveshaft rotation. Also described as waddle.

Shudder

A low-frequency vibration that is felt through the steering wheel or seat during light brake application.

Slap

A resonance from flat surfaces, such as safety belt webbing or door trim panels.

Slip Yoke/Slip Spline

The driveshaft coupling that allows length changes to occur while the suspension articulates and while the driveshaft rotates.

Squeak

A high-pitched transient sound, similar to rubbing fingers against a clean window.

Squeal

A long-duration, high-pitched noise.

Static Balance

The equal distribution of weight around the wheel. Statically unbalanced wheel and tire assemblies can cause a bouncing action called wheel tramp. This condition will eventually cause uneven tire wear.

Tap

A light, rhythmic, or intermittent hammering sound, similar to tapping a pencil on a table edge.

Thump

A dull beat caused by 2 items striking together.

Tick

A rhythmic tap, similar to a clock noise.

Tip-In Moan

A light moaning noise heard during light vehicle acceleration, usually between 40-100 km/h (25-65 mph).

TIR

The acronym for total indicated runout is TIR.

Tire Deflection

The change in tire diameter in the area where the tire contacts the ground.

Tire Flat Spots

A condition commonly caused by letting the vehicle stand while the tires cool off. This condition can be corrected by driving the vehicle until the tires are warm. Also, irregular tire wear patterns in the tire tread resulting from wheel-locked skids.

Tire Force Vibration

A tire vibration caused by variations in the construction of the tire that is noticeable when the tire rotates against the pavement. This condition can be present on perfectly round tires because of variations in the inner tire construction. This condition can occur at wheel rotation frequency or twice rotation frequency.

Transient

A noise or vibration that is momentary, a short duration.

Two-Plane Balance

Radial and lateral balance.

Vibration

Any motion, shaking or trembling, that can be felt or seen when an object moves back and forth or up and down.

Whine

A constant, high-pitched noise. Also described as a screech.

Whistle

High-pitched noise (above 500 Hz) with a very narrow frequency band. Examples of whistle noises are a turbocharger or airflow around an antenna.

Wind Noise

Any noise caused by air movement in, out or around the vehicle.

WOT

The acronym for wide open throttle is WOT.

Tools and Techniques

Electronic Vibration Analyzer (EVA)

The EVA is a hand-held electronic diagnostic tool which will assist in locating the source of unacceptable vibrations. The vibration sensor can be remotely mounted anywhere in the vehicle for testing purposes. The unit displays the 3 most common vibration frequencies and their corresponding amplitudes simultaneously. A bar graph provides a visual reference of the relative signal strength (amplitude) of each vibration being displayed and its relative G force. The keypad is arranged to make the EVA simple to program and use. Some of the functions include the ability to average readings as well as record, play back and freeze readings. The EVA has a strobe balancing function that can be used to detect imbalance on rotating components such as a driveshaft or engine accessories.

Scheme 5

The EVA allows for a systematic collection of information that is necessary to accurately diagnose and repair NVH problems. For the best results, carry out the test as follows

1. Test drive the vehicle with the vibration sensor inside the vehicle.
2. Place the sensor in the vehicle according to feel. If the condition is felt through the steering wheel, the source is most likely in the front of the vehicle. A vibration that is felt in the seat or floor only will most likely be found in the driveline, drive axle or rear wheels and tires.
3. Record the readings. Also note when the condition begins, when it reaches maximum intensity and if it tends to diminish above/below a certain speed. Frequencies should be read in the "average" mode. Frequencies have a range of plus or minus 2. A reading of 10 Hz can be displayed as an 8 Hz through 12 Hz. Frequencies with a reading of 0.06 hz or less, are barely perceptible NVH levels. No corrective action is necessary.
4. Place the vibration sensor on or near the suspect area outside the vehicle.
5. Continue the road test, driving the vehicle at the speed the symptom occurs, and take another reading.
6. Compare the readings. A match in frequency indicates the problem component or area. An unmatched test could indicate the concern is caused by the engine, torque converter or engine accessory. Use the EVA in the RPM mode and check if concern is RPM related. Example: A vibration is felt in the seat. Place the sensor on the console. Record the readings. Place the vibration sensor on the rear axle. Compare the readings. If the frequencies are the same, the axle is the problem component.

Vibrate Software(R)

Vibrate Software(R) (Rotunda tool number 215-00003) is a diagnostic aid which will assist in pinpointing the source of unacceptable vibrations. The engine's crankshaft is the point of reference for vibration diagnosis.

Every rotating component will have an angular velocity that is faster, slower or the same as the engine's crankshaft. Vibrate Software(R) calculates the angular velocity of each component and graphically represents these velocities on a computer screen and on a printed vibration worksheet. The following steps outline how Vibrate Software(R) helps diagnose a vibration concern

1. Enter the vehicle information. Vibrate will do all the calculations and display a graph showing tire, driveshaft and engine vibrations.
2. Print a Vibration Worksheet graph. The printed graph is to be used during the road test.
3. Road test the vehicle at the speed where the vibration is most noticeable. Record the vibration frequency (RPM) and the engine RPM on the worksheet graph. The point on the graph where the vibration frequency (RPM) reading and the engine RPM reading intersect indicates the specific component group causing the concern. An EVA or equivalent tool capable of measuring vibration frequency and engine RPM will be needed.
4. Provide pictures of diagnostic procedures to aid in testing components.

Combination EngineEAR/ChassisEAR

An electronic listening device used to quickly identify noise and the location under the chassis while the vehicle is being road tested. The ChassisEARs can identify the noise and location of damaged/worn wheel bearings, CV joints, brakes, springs, axle bearings or driveshaft carrier bearings.

EngineEAR Basic Unit

An electronic listening device used to detect even the faintest noises. The EngineEARs can detect the noise of damaged/worn bearings in generators, coolant pumps, A/C compressors and power steering pumps. They are also used to identify noisy lifters, exhaust manifold leaks, chipped gear teeth and for detecting wind noise. The EngineEAR has a sensing tip, amplifier and headphones. The directional sensing tip is used to listen to the various components. Point the sensing tip at the suspect component and adjust the volume with the amplifier. Placing the tip in direct contact with a component will reveal structure-borne noise and vibrations, generated by or passing through, the component. Various volume levels can reveal different sounds.

Ultrasonic Leak Detector

The Ultrasonic Leak Detector is used to detect wind noises caused by leaks and gaps in areas where there is weather-stripping or other sealing material. It is also used to identify A/C leaks, vacuum leaks and evaporative emission noises. The Ultrasonic Leak Detector includes a multi-directional transmitter (operating in the ultrasonic range) and a hand-held detector. The transmitter is placed inside the vehicle. On the outside of the vehicle, the hand-held detector is used to sweep the area of the suspected leak. As the source of the leak is approached, a beeping sound is produced which increases in both speed and frequency.

Squeak and Rattle Repair Kit

The squeak and rattle repair kit (Rotunda tool number 164-R4900) contains lubricants and self-adhesive materials that can be used to eliminate interior and exterior squeaks and rattles. The kit consists of the following materials

1. PVC (soft foam) tape
2. Urethane (hard foam) tape
3. Flocked (black fuzzy) tape
4. UHMW (frosted) tape
5. Squeak and rattle oil tube
6. Squeak and rattle grease tube

Tracing Powder

Tracing powder is used to check both the uniformity of contact and the tension of a seal against its sealing surface. These tests are usually done when a suspected air leak/noise appears to originate from the seal area or during the alignment and adjustment of a component to a weatherstrip. Tracing powder can be ordered from Crest Industries as ATR Leak Trace. Carry out the tracing powder test as follows

Scheme 6

1. Clean the weatherstrip.
2. Spray the tracing powder on the mating surface only.
3. Close the door completely. Do not slam the door.
4. Open the door. An imprint is made where the weatherstrip contacted the mating surface seal. Gaps or a faint imprint will show where there is poor contact with the weatherstrip.

Scheme 7

Index Card

Place an index card or a piece of paper between the weatherstrip and the sealing surface, then close the door. Slowly withdraw the index card or paper after the door is closed and check the amount of pressure on the weatherstrip. There should be a medium amount of resistance as it is withdrawn. Continue around the entire seal area. If there is little or no resistance, this indicates insufficient contact to form a good seal. At these points, the door, the glass or the weatherstrip is out of alignment.

Scheme 8

Scheme 9

To assist the service advisor and the technician, a Write-up Job Aid and an NVH Diagnostic Guide are included with this material. The Write-up Job Aid serves as a place to record all important symptom information. The NVH Diagnostic Guide serves as a place to record information reported on the Write-up Job Aid as well as data from the testing to be carried out.

To begin a successful diagnosis, fill out the NVH Diagnostic Guide, record the reported findings, then proceed to each of the numbered process steps to complete the diagnosis.

Scheme 10

Scheme 11

Scheme 12

Customer Interview

The diagnostic process starts with the customer interview. The service advisor must obtain as much information as possible about the concern and take a test drive with the customer. There are many ways a customer will describe NVH concerns and this will help minimize confusion arising from descriptive language differences. It is important that the concern is correctly interpreted and the customer descriptions are recorded. During the interview, ask the following questions

1. When was the concern first noticed?
2. Did the concern appear suddenly or gradually?
3. Did any abnormal occurrence coincide with or proceed its appearance?

Use the information gained from the customer to accurately begin the diagnostic process.

Pre-Drive Check

It is important to do a pre-drive check before road testing the vehicle. A pre-drive check verifies that the vehicle is relatively safe to drive and eliminates any obvious faults on the vehicle.

The pre-drive check consists of a brief visual inspection. During this brief inspection, take note of anything that will compromise safety during the road test and make those repairs or adjustments before taking the vehicle on the road.

Preparing for the Road Test

Observe the following when preparing for the road test

1. Review the information recorded on the NVH Diagnostic Guide. It is important to know the specific concern the customer has with the vehicle.
2. Do not be misled by the reported location of the noise or vibration. The cause can actually be some distance away, transferred from another part of the vehicle.
3. Remember that the vibrating source component (originator) may only generate a small vibration. This small vibration can in turn cause a larger vibration or noise to emanate from another receiving component (reactor), due to contact with other components (transfer path).
4. Conduct the road test on a quiet street where it is safe to duplicate the vibration or noise. The ideal testing route is an open, low-traffic area where it is possible to operate the vehicle at the speed in which the condition occurs.
5. If possible, lower the radio antenna in order to minimize turbulence. Identify anything that could potentially make noise or be a source of wind noise. Inspect the vehicle for add-on items that create vibration or noise. Turn off the radio and the heating and cooling system blower.
6. The engine speed is an important factor in arriving at a final conclusion. Therefore, connect an accurate tachometer to the engine, even if the vehicle has a tachometer. Use a tachometer that has clearly defined increments of less than 50 RPM. This ensures an exact engine speed reading.

Verify the Customer Concern

Verify the customer concern by carrying out a road test, an engine run-up test, or both.

The decision to carry out a road test, an engine run-up test, or both depends on the type of NVH concern. A road test may be necessary if the symptom relates to the suspension system or is sensitive to torque. A Drive Engine Run-Up (DERU) or a Neutral Engine Run-Up (NERU) Test identifies noises and vibrations relating to engine and drivetrain RPM. Remember, a condition will not always be identifiable by carrying out these tests, however, they will eliminate many possibilities if carried out correctly.

Road Test

Note. It may be necessary to have the customer ride along or drive the vehicle to point out the concern. During the road test, take into consideration the customer's driving habits and the driving conditions. The customer's concern just may be an acceptable operating condition for that vehicle.

The following is a brief overview of each test in the order in which it appears. A review of this information helps to quickly identify the most appropriate process necessary to make a successful diagnosis. After reviewing this information, select and carry out the appropriate test(s), proceeding to the next step of this process.

1. The Slow Acceleration Test is normally the first test to carry out when identifying an NVH concern, especially when a road test with the customer is not possible.
2. The Heavy Acceleration Test helps to determine if the concern is torque-related.
3. The Neutral Coast Down Speed Test helps to determine if the concern is vehicle speed-related.
4. The Downshift Speed Test helps to determine if the concern is engine speed-related.
5. The Steering Input Test helps to determine how the wheel bearings and other suspension components contribute to a vehicle speed-related concern.
6. The Brake Test helps to identify vibrations or noise that are brake related.
7. The Road Test Over Bumps helps isolate a noise that occurs when driving over a rough or bumpy surface.
8. The Engine Run-Up Tests consist of the Neutral Run-Up Test and the Engine Load Test. These tests help to determine if the concern is engine speed-related.
9. The Neutral Run-Up Test is used as a follow-up test to the Downshift Speed Test when the concern occurs at idle.
10. The Engine Load Test helps to identify vibration or noise sensitive to engine load or torque. It also helps to reproduce engine speed-related concerns that cannot be duplicated when carrying out the Neutral Run-Up Test or the Neutral Coast Down Test.
11. The Engine Accessory Test helps to locate faulty belts and accessories that cause engine speed-related concerns.
12. The Vehicle Cold Soak Procedure helps to identify concerns occurring during initial start-up and when an extended time lapse occurs between vehicle usage.

Slow Acceleration Test

To carry out this test, proceed as follows

1. Slowly accelerate to the speed where the reported concern occurs. Note the vehicle speed, the engine RPM and, if possible, determine the vibration frequency.
2. Attempt to identify from what part of the vehicle the concern is coming.
3. Attempt to identify the source of the concern.
4. Proceed as necessary.

Heavy Acceleration Test

To carry out this test, proceed as follows

1. Accelerate hard from 0-64 km/h (0-40 mph).
2. Decelerate in a lower gear.
3. The concern is torque related if duplicated while carrying out this test.
4. Proceed as necessary.

Neutral Coast Down Speed Test

To carry out this test, proceed as follows

1. Drive at a higher rate of speed than where the concern occurred when carrying out the Slow Acceleration Test.
2. Place the transmission in NEUTRAL and coast down past the speed where the concern occurs.
3. The concern is vehicle speed-related if duplicated while carrying out this test. This eliminates the engine and the torque converter as sources.
4. If the concern was not duplicated while carrying out this test, carry out the Downshift Speed Test to verify if the concern is engine speed-related.
5. Proceed as necessary.

Downshift Speed Test

To carry out this test, proceed as follows

1. Shift into a lower gear than the gear used when carrying out the Slow Acceleration Test.
2. Drive at the engine RPM where the concern occurs.
3. The concern is engine speed-related if duplicated while carrying out this test. This eliminates the tires, wheels, brakes and the suspension components as sources.
4. If necessary, repeat this test using other gears and NEUTRAL to verify the results.
5. Proceed as necessary.

Steering Input Test

To carry out this test, proceed as follows

1. Drive at the speed where the concern occurs, while making sweeping turns in both directions.
2. If the concern goes away or gets worse, the wheel bearings, hubs, U-joints (contained in the axles of 4WD applications), and tire tread wear are all possible sources.
3. Proceed as necessary.

Brake Test

To carry out this test, proceed as follows

1. Warm the brakes by slowing the vehicle a few times from 80-32 km/h (50-20 mph) using light braking applications. At highway speeds of 89-97 km/h (50-60 mph), apply the brake using a light pedal force.
2. Accelerate to 89-97 km/h (55-60 mph).
3. Lightly apply the brakes and slow the vehicle to 30 km/h (20 mph).
4. A brake vibration noise can be felt in the steering wheel, seat or brake pedal. A brake noise can be heard upon brake application and diminish when the brake is released.

Road Test Over Bumps

To carry out this test, proceed as follows

1. Drive the vehicle over a bump or rough surface one wheel at a time to determine if the noise is coming from the front or the back and the left or the right side of the vehicle.
2. Proceed as necessary.

Neutral Engine Run-Up (NERU) Test

To carry out this test, proceed as follows

1. Install a tachometer.
2. Increase the engine RPM up from an idle to approximately 4,000 RPM while in PARK on front wheel drive vehicles with automatic transmissions, or NEUTRAL for all other vehicles. Note the engine RPM and, if possible, determine the vibration frequency.
3. Attempt to identify what part of the vehicle the concern is coming from.
4. Attempt to identify the source of the concern.
5. Proceed as necessary.

Drive Engine Run-Up (DERU) Load Test

To carry out this test, proceed as follows

1. Block the front and rear wheels.
2. Apply the parking brake and the service brake.
3. Install a tachometer.
4. Shift the transmission into DRIVE, and increase and decrease the engine RPM between an idle to approximately 2,000 RPM. Note the engine RPM and, if possible, determine the vibration frequency.
5. Repeat the test in REVERSE.
6. If the vibration or noise is duplicated when carrying out this test, inspect the engine and transmission or transaxle mounts.
7. If the concern is definitely engine speed-related, carry out the Engine Accessory Test to narrow down the source.
8. Proceed as necessary.

Engine Accessory Test

To carry out this test, proceed as follows

1. Remove the accessory drive belts.
2. Increase the engine RPM to where the concern occurs.
3. If the vibration or noise is duplicated when carrying out this test, the belts and accessories are not sources.
4. If the vibration or noise was not duplicated when carrying out this test, install each accessory belt, one at a time, to locate the source.

Vehicle Cold Soak Procedure

To carry out this procedure, proceed as follows

1. Test preparations include matching customer conditions (if known). If not known, document the test conditions: gear selection and engine RPM. Monitor the vibration or noise duration with a watch for up to three minutes.
2. Park the vehicle where testing will occur. The vehicle must remain at or below the concern temperature (if known) for 6-8 hours.
3. Before starting the engine, conduct a visual inspection under the hood.
4. Turn the key on, but do not start the engine. Listen for the fuel pump, anti-lock brake system (ABS) and air suspension system noises.
5. Start the engine.
6. Isolate the vibration or noise by carefully listening. Move around the vehicle while listening to find the general location of the vibration or noise. Then, search for a more precise location by using a stethoscope or EngineEAR.
7. Refer to Idle Noise/Vibration in the Symptom Chart to assist with the diagnosis.

Check TSBs

After verifying the customer concern, check for TSBs and the vehicle repair history for related concerns. If information relating to a diagnosis or repair is found, carry out the procedure(s) specified in that information.

If no information is available from these sources, carry out the vehicle preliminary inspection to eliminate any obvious faults.

Diagnostic Procedure

Qualifying the concern by the particular sensation present can help narrow down the concern. Always use the "symptom" to "system" to "component" to "cause" diagnosis technique. This diagnostic method divides the problem into related areas to correct the customer concern.

1. Verify the "symptom".
2. Determine which "system(s)" can cause the "symptom". If a vibration concern is vehicle speed-related, the tire and wheel RPM/frequency or driveshaft frequency should be calculated. If a vibration concern is engine speed-related, the engine, engine accessory or engine firing frequencies should be calculated.
3. After determining the "system", use the diagnostic tools to identify the worn or damaged "components".
4. After identifying the "components", try to find the "cause" of the failure.

Once the concern is narrowed down to a symptom or condition, proceed to NVH Condition and Symptom Categories.

NVH Condition and Symptom Categories

A good diagnostic process is a logical sequence of steps that lead to the identification of a causal system. Use the condition and symptom categories as follows

1. Identify the operating condition that the vehicle is exhibiting.
2. Match the operating condition to the symptom.
3. Verify the symptom.
4. Identify which category or system could cause the symptom.
5. Refer to the diagnostic symptom chart that is referred to.

Operating Condition-Vehicle is Not Moving

1. Static operation Noise occurs during component/system functioning. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Squeak and Rattle.
2. While cranking Grinding or whine, differential ring gear or starter motor pinion noise. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Rattle. Exhaust hanger, exhaust heat shield or A/C line noise. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Squeak and Rattle. Vibration. Acceptable condition.
3. At idle Idle noise. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Idle Noise/Vibration. Idle vibration or shake. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Idle Noise/Vibration.
4. During Gear Selection Vehicle parked on a steep incline. Acceptable noise. Vehicle parked on a flat surface. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Driveline Noise/Vibration.

Operating Condition-Vehicle is Moving

1. Depends more on how the vehicle is operated Speed-related Related to vehicle speed Pitch increases with vehicle speed. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Tire Noise/Vibration. Noise occurs at specific vehicle speed. A high-pitched noise (whine). GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Driveline Noise/Vibration. Loudness proportional to vehicle speed. Low-frequency noise at high speeds, noise and loudness increase with speed. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Driveline Noise/Vibration. A low-pitched noise (drumming). GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Vibration occurs at a particular speed (mph) regardless of acceleration or deceleration. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Tire Noise/Vibration. Noise varies with wind/vehicle speed and direction. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Air Leak and Wind Noise. Related to engine speed. Noise varies with engine RPM. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Vibration occurs at a particular speed (mph) regardless of engine speed (RPM). Acceleration Wide open throttle (WOT) Engine induced contact between components. Inspect and repair as necessary. Noise is continuous throughout WOT. Exhaust system or engine ground out. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Light/moderate acceleration Tip-in moan. Engine/exhaust noise. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Knock-type noise. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Driveline shudder. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Engine vibration. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Turning noise. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Steering Noise/Vibration. Braking Clicking sound is signaling ABS is active. Acceptable ABS sound. A continuous grinding/squeal. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Brake Noise/Vibration. Brake vibration/shudder. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Brake Noise/Vibration. Shifting Noise or vibration condition related to the transmission (automatic). GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Transmission (Automatic) Noise/Vibration. Cruising speeds Accelerator pedal vibration. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Engine Noise/Vibration. Driveline vibration. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Driveline Noise/Vibration. A shimmy or shake. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Tire Noise/Vibration. Driving at low/medium speeds A wobble or shudder. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Tire Noise/Vibration.
2. Depends more on where the vehicle is operated Bump/pothole, rough road or smooth road. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Suspension Noise/Vibration. Noise is random or intermittent occurring from road irregularities. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Squeak and Rattle. Noise or vibration changes from one road surface to another. Normal sound changes. Noise or vibration associated with a hard/firm ride. GO to «Symptom Charts»(/ford/crown-victoria/ii-1997-2011/remont/oem-general-information/#noise-vibration-harshness) - Suspension Noise/Vibration.

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Pinpoint Tests

The pinpoint tests are a step-by-step diagnostic process designed to determine the cause of a condition. It may not always be necessary to follow a pinpoint test to its conclusion. Carry out only the steps necessary to correct the condition. Then, test the system for normal operation. Sometimes, it is necessary to remove various vehicle components to gain access to the component requiring testing. For additional information, refer to the appropriate article for removal and installation procedures. Reinstall all components after verifying system operation is normal.

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IDLE AIR CONTROL (IAC) VALVE

1. Open the hood.
2. Verify the condition by operating the vehicle for a short time.
3. Inspect the IAC valve. If physical evidence of contamination exists, install a new IAC valve.
4. While the noise is occurring, either place an EngineEAR probe near the IAC valve and the inlet tube, or create a 6.35 mm (0.25 in)-12.7 mm (0.50 in) air gap between the inlet tube and the clean air tube. If the IAC valve is making the noise, install a new IAC valve.
5. Test the vehicle for normal operation.

STEERING GEAR GRUNT/SHUDDER TEST

1. Start and run the vehicle to operating temperature.
2. Set engine idle speed to 1200 RPM.
3. Rotate the steering wheel to the RH stop, then turn the steering wheel 90 degrees back from that position. Turn the steering wheel slowly in a 15 degree to 30 degree arc.
4. Turn the steering wheel another 90 degrees. Turn the steering wheel slowly in a 15 degree to 30 degree arc.
5. Repeat the test with power steering fluid at different temperatures.
6. If a light grunt is heard or a low (50-200 Hz) shudder is present, this is a normal steering system condition.
7. If a loud grunt is heard, or a strong shudder is felt, fill and purge the power steering system.

CHECKING TOOTH CONTACT PATTERN AND CONDITION OF THE RING AND PINION

There are two basic types of conditions that will produce ring and pinion noise. The first type is a howl or chuckle produced by broken, cracked, chipped, scored or forcibly damaged gear teeth and is usually quite audible over the entire speed range. The second type of ring and pinion noise pertains to the mesh pattern of the gear pattern. This gear noise can be recognized as it produces a cycling pitch or whine. Ring and pinion noise tends to peak in a narrow speed range or ranges, and will tend to remain constant in pitch.

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1. Raise and support the vehicle. For additional information, refer to «JACKING & LIFTING»(/ford/crown-victoria/ii-1997-2011/remont/hoistjack/#jacking-lifting) .
2. Drain the axle lubricant. For additional information, refer to «REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8 INCH RING GEAR»(/ford/crown-victoria/ii-1997-2011/remont/differentials-drive-axles/#rear-drive-axledifferential-ford-88-inch-ring-gear) .
3. Remove the carrier assembly or the axle housing cover depending on the axle type. For additional information, refer to «REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8 INCH RING GEAR»(/ford/crown-victoria/ii-1997-2011/remont/differentials-drive-axles/#rear-drive-axledifferential-ford-88-inch-ring-gear) .
4. Inspect the gear set for scoring or damage.
5. In the following steps, the movement of the contact pattern along the length is indicated as toward the "heel" or "toe" of the differential ring gear.
6. Apply a marking compound to a third of the gear teeth on the differential ring gear. Rotate the differential ring gear several complete turns in both directions until a good, clear tooth pattern is obtained. Inspect the contact patterns on the ring gear teeth.
7. A good contact pattern should be centered on the tooth. It can also be slightly toward the toe. There should always be some clearance between the contact pattern and the top of the tooth. Tooth contact pattern shown on the drive side of the gear teeth.
8. A high, thick contact pattern that is worn more toward the toe. Tooth contact pattern shown on the drive side of the gear teeth. The high contact pattern indicates that the drive pinion is not installed deep enough into the carrier. The differential ring gear backlash is correct, a thinner drive pinion shim is needed. A decrease will move the drive pinion toward the differential ring gear.
9. A high, thin contact pattern that is worn toward the toe. Tooth contact pattern shown on the drive side of the gear teeth. The drive pinion depth is correct. Increase the differential ring gear backlash.
10. A contact pattern that is worn in the center of the differential ring gear tooth toward the heel. Tooth contact pattern shown on the drive side of the gear teeth. The low contact pattern indicates that the drive pinion is installed too deep into the carrier. The differential ring gear backlash is correct. A thicker drive pinion shim is needed.
11. A contact pattern that is worn at the top of the differential ring gear tooth toward the heel. Tooth contact pattern shown on the drive side of the gear teeth. The pinion gear depth is correct. Decrease the differential ring gear backlash.

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Wheel and tire NVH concerns are directly related to vehicle speed and are not generally affected by acceleration, coasting or decelerating. Also, out-of-balance wheel and tires can vibrate at more than one speed. A vibration that is affected by the engine RPM, or is eliminated by placing the transmission in NEUTRAL is not related to the tire and wheel. As a general rule, tire and wheel vibrations felt in the steering wheel are related to the front tire and wheel assemblies. Vibrations felt in the seat or floor are related to the rear tire and wheel assemblies. This can initially isolate a concern to the front or rear.

Careful attention must be paid to the tire and wheels. There are several symptoms that can be caused by damaged or worn tire and wheels. Carry out a careful visual inspection of the tires and wheel assemblies.

Spin the tires slowly and watch for signs of lateral or radial runout. For additional information, refer to the tire wear chart to determine the tire wear conditions and actions.

For a vibration concern, use the vehicle speed to determine tire/wheel frequency and RPM. Calculate tire and wheel RPM and frequency by carrying out the following

1. Measure the diameter of the tire.
2. Record the speed at which the vibration occurs.
3. Obtain the corresponding tire and wheel RPM and frequency from the Tire Speed and Frequency Chart. If the vehicle speed is not listed, divide the vehicle speed at which the vibration occurs by 16 km/h (10 mph). Multiply that number by 16 km/h (10 mph) tire RPM listed for that tire diameter in the chart. Then divide that number by 60. For example: a 40 mph vibration with 835 mm (33 in) tires. 40\10 = 4. Multiply 4 by 105 = 420 RPM. Divide 420 RPM by 60 seconds = 7 Hz at 40 mph.

TIRE SPEED AND FREQUENCY

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MATERIAL SPECIFICATIONS

1. Check wheel bearing end-play and correct as necessary.
2. Remove the tire and wheel assembly.
3. Remove the brake caliper and the brake caliper anchor plate. Refer to «DISC»(/ford/crown-victoria/ii-1997-2011/remont/mechanical-hydraulic/#disc-brakes) for the procedure.
4. Inspect the brake linings. Install new brake linings if below specification. For additional information, refer to the appropriate brake article.
5. Measure and record the brake disc thickness. Install a new brake disc if the thickness after machining will be at or below specification. The specification is molded into the brake disc. Do not machine a new brake disc.
6. For vehicles with a 2-piece hub and brake disc assembly: Match-mark before disassembly. Remove the brake disc. Clean the hub and brake disc mounting surfaces with metal surface cleaner. Using a die grinder with a mild abrasive (Scotch Brite(R) type), remove any rust or corrosion from the hub and brake disc mounting surfaces. Align the match-marks and reinstall the brake disc on the hub.
7. Using an on-car brake lathe, machine the brake discs. Follow the manufacturer's instructions. After machining, make sure the brake disc still meets the thickness specification.
8. Using the special tools, verify that the brake disc lateral runout is now within specification. For additional information, refer to «BRAKE SYSTEM-GENERAL INFORMATION»(/ford/crown-victoria/ii-1997-2011/remont/anti-locktraction-control/#brake-system-general-information) .
9. Remove the special tool hub adapter.
10. Remove any remaining metal chips from the machining operation.
11. For vehicles with a 2-piece hub and brake disc assembly: Remove the brake disc from the hub. Remove any remaining metal chips from hub and brake disc mounting surfaces and from the ABS sensor. Apply a liberal amount of lubricant to the hub flange, pilot area and to the brake disc-to-hub mounting surface. Using the match marks, mount the brake disc on the hub.
12. Install the brake caliper anchor plate and the brake caliper.
13. Install the tire and wheel assembly.
14. Test the system for normal operation.

Powertrain/Drivetrain Mount Neutralizing

1. With the vehicle in NEUTRAL, position it on a hoist. For additional information, refer to «JACKING & LIFTING»(/ford/crown-victoria/ii-1997-2011/remont/hoistjack/#jacking-lifting) .
2. Loosen, but do not remove, the powertrain/drivetrain mount fasteners.
3. Lower the vehicle.
4. Move the vehicle in FORWARD and REVERSE 0.6-1.2 meters (2-4 ft).
5. With the vehicle in NEUTRAL, position it on a hoist. For additional information, refer to «JACKING & LIFTING»(/ford/crown-victoria/ii-1997-2011/remont/hoistjack/#jacking-lifting) .
6. Tighten the powertrain/drivetrain mount fasteners.
7. Lower the vehicle.
8. Test the system for normal operation.

Exhaust System Neutralizing

Note. Neutralize the exhaust system to relieve strain on mounts which can be sufficiently bound up to transmit vibration as if grounded.

1. With the vehicle in NEUTRAL, position it on a hoist. For additional information, refer to «JACKING & LIFTING»(/ford/crown-victoria/ii-1997-2011/remont/hoistjack/#jacking-lifting) .
2. Loosen all exhaust hanger attachments and reposition the hangers until they hang free and straight.
3. Loosen all exhaust flange joints.
4. Place a stand to support the muffler parallel to the vehicle frame with the muffler pipe bracket free of stress.
5. Tighten the muffler connection.
6. Tighten all the exhaust hanger clamps and flanges (tighten the exhaust manifold flange joint last). Verify there is adequate clearance to prevent grounding at any point in the system. Make sure that the catalytic converter and heat shield do not contact the frame rails. After neutralization, the rubber in the exhaust hangers should show some flexibility when movement is applied to the exhaust system. With the exhaust system installed securely and cooled, the rear hanger should be angled forward.
7. Lower the vehicle.
8. Test the exhaust system for normal operation.

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1. Raise the vehicle until the front tires are off the floor. Make sure the wheels are in a straight forward position.
2. Spin the tire by hand to check the wheel bearings for roughness.
3. Grip each front tire at the top and bottom and move the wheel inward and outward while lifting the weight of the tire off the front wheel bearing.
4. If the tire and wheel (hub) is loose on the spindle, does not rotate freely, or has a rough feeling when spun, carry out one of the following: On vehicles with inner and outer bearings, inspect the bearings and cups for wear or damage. Adjust or install new bearings and cups as necessary. On vehicles with one sealed bearing, install a new wheel hub.

See also:
• JACKING & LIFTING
• REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8 INCH RING GEAR
• DISC
• BRAKE SYSTEM-GENERAL INFORMATION
• Symptom Charts