Vehicles can confound their owners with a variety of noises that come from one end of the vehicle or the other. Some noises can be temporary or sporadic, coming and going during different times of operation. These intermittent noises can be the most difficult to diagnose. Other noises start gradually and get progressively worse, which can tip off the vehicle owner to some potentially serious problems. Knowing what noises mean and their location can prevent costly repairs down the road.
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Things you need
- Automotive stethoscope
- Floor jack
- Jack stands
- Shop rag
Drive your vehicle in an alleyway that has high walls on both sides. The narrower the alley, the better. High walls in proximity to the vehicle amplify sounds, making them very easy to hear. Roll all the windows down and listen carefully for anything that sounds unusual. Listen for squeaks, knocking, clacking, clicking, "plapping," hissing, grinding or swishing noises. Record any peculiar noises in a notebook, noting the noise and the approximate or exact location where it comes from. Make several passes with the vehicle.
Apply the brakes slowly while driving in the alleyway. If you detect any swishing or metal-to-metal grinding noises while applying the brakes, this means that the disc pads or the rear drum shoes have worn down past their useful life.
Listen for any clicking sounds that come from any one of the wheels while driving in the alleyway. Loose hubcaps, especially ones with a spoke-wheel design, will make such noises. The suspect wheel can be eliminated by removing the hubcaps one at a time to narrow down the clicking wheel. This clicking noise should not be confused with worn hydraulic lifters or rocker arms which will originate from the engine and not the wheels.
Drive the vehicle over parking stops at a slow speed. Listen for any hard clunking noises that come from the vicinity of the front suspension. Such noises could indicate a broken shock mount, a worn upper or lower ball joint, or bad or broken control arm bushings that have bottomed out the frame. The noises will be jarring or harsh-sounding.
Park the vehicle with the engine off and the emergency brake set. Move to the front of the vehicle and raise the hood. With the full weight of your body, step on the bumper and push downward. Listen for any squeaking sounds. Such noises indicate that the control arm bushings have dried out, or that the coil springs have shifted and become unseated. Dry ball joints will produce a squeak. Sometimes an anti-sway bar or idler arm will squeak as a result of wear or a dry joint.
Listen to any noises coming from the radiator while the engine is running. A stuck thermostat will produce a knocking noise that comes from the top of the radiator. A noticeable vibration can also be felt but be sure to use a rag instead of a bare hand to feel it.
Drive down the street under normal conditions. Listen for any sound that simulates a whining noise that increases with intensity or decreases with the automatic shifting of the transmission. This whining noise usually indicates a low transmission fluid level or contaminated fluid. This noise might be very similar to a power steering pump, except that a power steering pump might screech or howl much louder.
Place an automotive stethoscope over the top of the engine while it idles. Any clicking or clacking sounds coming from the valve covers or the intake manifold usually point to a stuck or worn hydraulic lifter, or a solid lifter out of adjustment. Remember that the camshaft (valve train parts) move at half the speed of the crankshaft, so for every two engine rotations, the camshaft will rotate once.
Move the stethoscope down to the side of the engine block with the engine running. Any muffled clanking noise within denotes a piston connecting rod that has worn on its piston journal or the crankshaft journal. These internal, heavy engine knocks will point to the main bearings, the crankshaft or pistons. This noise will be constant and frequent every time the engine rotates.
Turn on the air conditioning and listen for any screeching noises coming from the engine compartment. Such a noise points to a loose serpentine belt or AC pulley belt slipping on the pulley.
Listen for any backfire engine noise that produces a very loud popping sound during acceleration or braking. This indicates a timing problem associated with a bad timing chain tensioner, a loose timing chain or belt, or a chain or belt that has skipped time.
Raise the vehicle on jack stands and run the engine in gear, listening for any "growling" sounds coming from the driving wheels. Such noises usually denote a worn or dry wheel bearing.
Tips and warnings
- Keeping a notebook to record noises, what they sound like and their location can help a mechanic diagnose the probable causes, especially with an intermittent noise that comes and goes.
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