How o Troubleshoot Automobile Chassis Parts


Diagnosing chassis noises can be one of the most frustrating problems technicians face. Fortunately, manufacturers have engineered noise, vibration and harshness diagnostic techniques and equipment to find the source of the noise generated by automobile chassis parts.

In the aftermarket, the causes are generally repair oversights, worn parts and normal wear, and the most successful shops take a structured approach to diagnosing these problems. In this article, we will discuss the need to carefully gather information from the customer before conducting a thorough bumper-to-bumper inspection of multiple drivetrain and chassis systems and components. One of the most important things to remember while doing the bumper-to-bumper inspection is to continue searching after finding a problem.

For older, high-mileage vehicles, start the procedure by lubricating the latches in doors, trunk, and hood. It is also recommended to lubricate rubber door seals and plastic parts with an aerosol silicone spray. Always check for obvious drivetrain or chassis clunking by performing a preliminary parking lot test of shifting, steering, and braking. Underhood checks should include unsecured batteries, hoses and other hard part that may rattle while driving. The trunk should also be checked for loose spare tires, jacking equipment, and other paraphernalia that could make noise.

When beginning the underbody inspection, remember that exhaust systems are vulnerable to road damage and inexperienced repairs, therefore, exhaust and catalytic converter shielding is a good place to start the search for the noise source. Exhaust pipe causes noise due to it expanding and coming in contact with other parts, a good measure is to allow enough space for your hand to fit between the pipe, muffler, and body.

In addition, check the exhaust hangers for proper function. Catalytic converters can produce noises when the substrate separates from the shell. If the converter rattles when tapped, the substrate is loose. Also, make sure the flex joint between the exhaust outlet and the converter is secure. Last, spray all rubber parts with an aerosol silicone compound. Silicone helps to quiet small irritating noises.

Generally, automobile chassis noises fall into different categories. First would be the “tar-strip” chucking noise, most noticeable when the wheel strikes an irregularity in the road surface. Loose or broken exhaust and suspension components often cause the chucking noise. These noises can be duplicated in shop by jouncing the car. When jouncing the vehicle, use your knee on the bumper to avoid sheet metal damage.

A drive on lift is very helpful for suspension inspection. You can try to duplicate the noises by applying power or braking on the lift. Keep in mind that the suspension absorbs all the force. Last, check conventional engine mounts, torque struts, and other rubber powertrain mountings. Small metal-to-metal contact can cause a major noise complaint.

Since noise is easily transferred through the suspension and Automobile Chassis Parts, it is best to use strategically placed electronic listening equipment to find chassis and drivetrain noises.