BMW 740Li Suspension System Inspect Cost

Suspension systems have existed long before automobiles were invented, and still serve the same function. Albeit they have become much more advanced, the basic functions are to support the body of the vehicle and absorb the impact and vibrations encountered while driving. Modern vehicles have enhanced this focus to include improved handling characteristics, increase body control in many conditions, and allow the vehicle to traverse even the worst terrains. Being as the entire weight of the vehicle rests on the suspension, these issues manifest themselves in obvious manners. When an problem presents itself, a suspension inspection will likely identify the issue right away.

The suspension system operates based on spring pressure and moveable components. Spring pressure allows the suspension to hold the weight of the vehicle, and keeps the vehicle in a raised position. This spring pressure may lift the vehicle by a control arm of the wheel spindle, but in either case it performs the same function. The suspension must absorb shock and flex over bumps, so moving joints are used in most areas of the suspension system. To allow the wheels to move up and down, control arms are secured to the chassis and allowed to pivot up and down. Next, the spindles connect to the control arms vie flexible joints called ball joints, which allow the spindles to turn for steering wheels, and prevent binding when the control arm moves up and down. Next, sway bars are used to connect the control arms on both sides of the vehicle and the frame of the vehicle. This flexible bar prevents the control arm on one side of the vehicle from moving without the other control arm compensating as well. This allows for controlled turns with limited body roll. Finally, shocks are used, either between the control arm and frame or as part of a strut assembly, to dampen the movement of the suspension and control bouncing motions. This entire system can be much more complicated, so when a suspension problem presents itself, inspection will be necessary to identify the cause.

Suspension system malfunctions have several symptoms that may be notices. Noises like clunks, scrapes, dragging noises, rubbing, creaking, and rattles may be heard when various components in the suspension system fail. Vibration is also a common issue, and it is generally felt in the steering wheel, brake pedal or floorboard of the vehicle. Next, the vehicle may seem to go where it wants while driving in a straight line. This is called wandering, and a worn suspension components can easily cause this concern. Last, but not least, body control may be completely compromised by a vehicle that feels as though it is floating down the road, leans hard during turns, seems to shift when accelerating, braking or turning, or nosedives on braking.

Some suspension issues can wait to be repaired at a more opportune time, but many other suspension issues call for immediate attention. When safety is the concern, do not wait to address the issue. Slight noises that come and go are not required to fix right away, however, they will become larger as time moves on if they are caused by the suspension system. When suspension system failures lead to unpredictable driving conditions, instability, or loss of control, the issue should be taken seriously and repaired immediately.

The suspension system on most vehicles will be inspected regularly, whether or not the owner is aware. During most oil changes at full service shops, the servicing technician will conduct a visual inspection of the vehicle as the oil drains. If an error with the suspension is noticed, the technician will recommend hands on inspection in order to ensure safety. Unless the vehicle oil is changed at an oil change only facility, the suspension will likely receive a visual inspection at least every 10,000 miles.

Suspension components are typically diagnosed by listening for noises, feeling vibration, or noticing instability, noting when these conditions occur, and then using this information for a guided search for the culprit. In general, suspension components fail by allowing excess movement, making noise at the bushings, or by bending or breaking. All of these are found by visually inspecting, making comparisons from side to side, manually moving parts, and placing pressure at strategic locations in order to measure movement. When parts are found to be bent, broken, leaking lubrication, cracking, deteriorating, or loose, they will be diagnosed as faulty in most cases.

Suspension component replacement in most cases requires the vehicle to be raised, the wheels removed, and specialty pullers and separator tools to remove damaged components. This can be physically demanding and dangerous work. Coil springs must be properly harnessed and relieved of tension, and care must be taken to prevent damage to adjoining components. Once suspension parts are replaced, an alignment check will typically be needed to ensure the new parts will not cause excessive tire wear.

We recommend using only high quality or OEM suspension components. Many aftermarket components are made with economy in mind instead of longevity, and vehicles using poorly made components are likely candidates for additional repairs in the near future.

Repairing many portions of the suspension system will involve removing a coil spring assembly. This is not just dangerous, it can be deadly. Coil springs are preloaded with enough force to hold a vehicle, and releasing a spring improperly can cause damage to property, self or others.

Suspension repair will often require specialty tools to separate components from one another, capture coil springs, and seat new parts. Also, using these tools assumes a degree of knowledge suitable to prevent damage and injury to the servicing technician. If proper procedures are not followed, the job is not understood, or the proper tooling is unavailable, the job should be trusted to a certified technician.