- Idle air control (IAC) valve moan - occurs on throttle tip-out
|
- IAC valve is contaminated with oil.
|
|
- Accessory drive belt chirp - occurs at idle or high idle, cold or hot. Most common occurrence is during humid weather
|
- Accessory drive belt worn, or pulley is misaligned or loose.
|
- INSPECT for loose or misaligned pulleys. CHECK the drive belt for wear or damage. INSTALL new pulley(s)/accessory drive component or drive belt, as necessary. REFER to ACCESSORY DRIVE
.
|
- Accessory drive bearing hoot - occurs at idle or high idle in cold temperatures of approximately +4°C (+40°F) or colder at first start of the day
|
- Accessory drive idler or tensioner pulley bearing is experiencing stick/slip between ball bearings and bearing race.
|
|
- Power steering moan - occurs at high idle and possibly at idle during the first cold start of the day in temperatures of approximately -18°C (0°F) or colder. Noise can even be a severe screech for less than one minute in very cold temperatures of approximately -29°C (-20°F) or colder
|
- High fluid viscosity, or plugged reservoir screen in power steering reservoir starves pump causing cavitation.
|
|
- Generator whine - during high electrical loads at idle or high idle, a high pitch whine or moan is emitted from the generator
|
- Generator electrical field noise.
|
- Using an EngineEAR, PROBE near the generator housing. LISTEN for changes in the noise level while changing electrical loads (such as rear defrost, headlamps, etc.). CARRY OUT a generator load test. If the system passes the load test, the noise is from the generator bearings, INSTALL new bearings. If the system fails the load test, INSTALL a new generator. REFER to GENERATOR AND REGULATOR
for 95 and 130 amp generators. REFER to GENERATOR AND REGULATOR
for 7.3L diesel dual generators.
|
- Engine-driven cooling fan moan - occurs during the first start of the day. It is most objectionable near idle speeds up to 2000 rpm. The noise increases with rpm
|
- The viscous cooling fan clutch engages until the fluid in the clutch reaches normal operating temperature, causing the fan to fully engage.
|
|
- Drumming noise - occurs inside the vehicle during idle or high idle, hot or cold. Very low-frequency drumming is very rpm dependent
|
- Exhaust system vibration excites the body resonances inducing interior noise.
- Engine vibration excites the body resonances inducing interior noise.
|
|
- Hissing noise - occurs during idle or high idle that is apparent with the hood open
|
- Vacuum leak or idle air control (IAC) valve flow noise.
|
- Use the Ultrasonic Leak Detector/EngineEAR to locate the source. Scan the air intake system from the inlet to each cylinder intake port. DISCARD the leaking parts, and INSTALL a new component.
|
- Vehicles with a plastic intake manifold.
|
- Acceptable condition. Some plastic manifolds exhibit this noise, which is the effect of the plastic manifold.
|
- Automatic transmission buzz or hiss
|
- Incorrect driveline angles.
|
|
- Worn or damaged main control solenoids or valves.
|
|
- Manual Transmission Clutch throw-out bearing whine. A change in noise pitch or loudness while depressing the clutch pedal
|
|
- INSTALL a new throw-out bearing.
|
- Heating, vacuum and air conditioning (HVAC) system chirp - most audible inside the vehicle. Listen for a change in noise pitch or loudness while changing the HVAC system blower speed
|
- Damaged or worn HVAC blower bearing.
|
|
- Air conditioning (A/C) clutch ticking - occurs when the compressor clutch engages
|
- Acceptable noise.
- Incorrect air gap.
|
- LISTEN to the clutch to determine if the noise occurs with clutch engagement. A small amount of noise is acceptable. If the noise is excessive, CHECK the A/C clutch air gap. INSPECT the A/C clutch for wear or damage. INSTALL a new clutch as necessary. REFER to AIR CONDITIONING
.
|
- Intermittent rattle, or scraping/rubbing noise
|
- Loose exhaust heat shield(s).
|
- INSPECT the exhaust system for loose parts using a glove or clamps to verify cause. REPAIR as necessary. REFER to EXHAUST SYSTEM
.
|
- Wiring, hose or other part interfering with accessory drive, drive belt or pulley.
|
- INSPECT accessory drive system closely verifying there is adequate clearance to all rotating components. REPAIR as necessary.
|
- Engine ticking or knocking noise - occurs during idle or high idle during the first cold start of the day
|
- Piston noise or valvetrain noise (bled down lifter/lash adjuster).
|
|
- A continuous, speed-dependent rattle from the engine - occurs during idle or high idle during the first cold start of the day and disappears as the engine warms up
|
- Piston noise or valvetrain noise (bled down lifter/lash adjuster).
|
|
- Idle vibration - a low-frequency vibration (5-20 Hz) or mild shake that is felt through the seat/floorpan
|
|
|
- Engine or torque converter out of balance.
|
|
- Idle vibration - a high-frequency vibration (20-80 Hz) or buzz, that is felt through the steering wheel or seat
|
- Exhaust system mounts bound up.
|
- VERIFY concern occurs at engine firing frequency. CHECK that the exhaust system vibrates at the same frequency as the engine. ADD 9-14 km (20-30 lb.) to the tail pipe to test, CARRY OUT Exhaust System Neutralizing .
|
|
|
- INSPECT the body mounts. CARRY OUT a Neutral Engine Run-Up (NERU) Test. REPAIR as necessary
|
- Power steering lines grounded out.
|
- INSPECT that the power steering lines are not contacting the chassis or each other. REPAIR as necessary.
|