Auto Service Professional

JUN 2018

Magazine for the auto service professional

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Page 46 of 69

J u n e 2 018 A SP 45 to the next clock position and re-check. It may be possible to find that "sweet spot" where hub runout and rotor runout cancel each other out. A "noise" complaint has the potential for cov- ering quite a lot of ground. Try to obtain more detailed information from the customer. What type of noise do you hear? (clicking, groaning, grinding, popping, whirring, whistling, chirp- ing, banging, etc.). When do you hear the noise? (while starting the engine, while cruising, during braking or turning, or when braking). Worn front wheel bearings will typically produce a grinding or clicking sound. Worn or damaged upper strut bearings will typically produce grinding, squeaking or popping noises best heard during slow turns. Worn or dry CV joints will cause a clicking noise, usually expe- rienced during a slow turn (into a driveway or parking spot). If the vehicle features front-wheel drive and the rear suspension features a Watts link (also called a bell crank), it's not uncommon for a worn Watts link center bushing to be worn out, which will result in a banging noise as the vehicle is driven over bumps or uneven road surfaces. is is oen misdiagnosed as involving loose or worn-out rear shocks/struts. A worn-out Watts link won't really cause any major drivability is- sues, but the resulting banging noise can be quite nerve-wracking, making the vehicle owner con- cerned about a major problem. A "quick & dirty" check when trying to iso- late a suspension noise is to unload the suspen- sion (car jacked up or on a frame li) and whack the center of the tire tread with a large hammer, while listening (and feeling with your hands) for noises at control arms, sway bar links, wheel bearings, etc. is basically allows you to at- tempt duplicating the tire hitting a pothole. is old-school technique can oen let you determine a worn suspension component. A "shake" complaint by the customer in somewhat ambiguous, since the issue may in- volve a vibration or a "shake." Potential wheel imbalance is an obvious starting point. A road test will help to confirm this. If you suspect a wheel imbalance, and you check the wheels on a balancing machine and find no issues, con- sider a road force variation issue, where the construction of the tire(s) features isolated hard spots. is may be verified and remedied by us- ing a balancing machine that features a road force simulator. Other potential factors might include a drive- sha imbalance. Inspect the drivesha for a missing balance weight and check for worn front and rear universal joints. Also inspect for a bent or dented drivesha. If the vehicle features rear- drive and a solid axle housing, check the pinion angle. If the axle assembly pinion angle has been moving vertically, this changes the drivesha an- gle, which could explain a shaking or vibrating issue. If the rear suspension features leaf springs, inspect the spring mounts and spring pad U- bolts for wear and looseness. While the LED lights provide a signal-strength visual aid when monitoring noises, the earphones provide the technician with a clear audible reference. This allows you to not only listen for unusual sounds, but to compare sounds from opposite sides of the vehicle (comparing brake calipers, wheel bearings at the same axle, control arms, etc.). The transmitters may be secured to the vehicle in one of three ways: by the built- in magnets, with the use of Velcro straps, or via the high-tension spring clamps located on the rear of the units.

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