Steering and Suspension A4 Flashcards

A vehicle with power steering has a groan or moan during low-speed parking maneuvers that goes away when the wheel is released to center. What is the MOST likely cause?

Answer: Air in the power steering hydraulic system

Air in the power steering system causes a groan or moan when the fluid is pumped through the steering gear under high-pressure demand (during parking maneuvers). The air creates noise as it is compressed and moved through the fluid. The noise stops when steering load is released.

Caster angle is described as positive when the steering axis tilts rearward at the top when viewed from the side. What is the PRIMARY function of positive caster?

Answer: To provide directional stability and self-centering of the steering wheel

Positive caster creates a mechanical trail — the point where the steering axis intersects the road is ahead of the tire contact patch center. This trail creates a self-aligning torque that straightens the steering after a turn and provides straight-line directional stability.

A technician is inspecting front ball joints on a vehicle with load-carrying ball joints (not wear-indicator type). The lower ball joint has 0.060 inches of axial play (up-and-down). The specification for replacement is greater than 0.050 inches. What should be done?

Answer: The joint must be replaced because it exceeds the maximum allowable play

Any measurement exceeding the manufacturer's maximum specification requires replacement. The joint has 0.060 inches of play while the replacement threshold is greater than 0.050 inches, meaning 0.060 exceeds the limit. There is no acceptable margin above a safety-critical specification.

What is the purpose of the steering angle sensor (SAS) in a modern vehicle equipped with electronic stability control (ESC)?

Answer: To provide steering wheel position data to the ESC system so it can compare intended direction with actual vehicle yaw

The steering angle sensor measures the position of the steering wheel and communicates it to the ESC module. The ESC system compares the driver's intended direction (from SAS) with the vehicle's actual yaw rate and lateral acceleration, applying individual brakes to correct oversteer or understeer.

A technician is checking front-end alignment and finds the vehicle has excessive positive camber on both sides. The vehicle has non-adjustable front suspension (no camber bolts or slots). What is the MOST likely cause of the excess camber?

Answer: Worn or collapsed front strut mounts or upper bearings

On vehicles without camber adjustments, the alignment angles are set by the geometry of the suspension components. Worn or collapsed strut mounts and upper bearings change the position of the top of the strut, effectively changing camber. If both sides show excessive positive camber, worn upper mounts are a common cause.

During a test drive for steering diagnosis, a technician notices the steering feels loose at highway speeds but is fine at low speeds. What is the primary cause of this speed-sensitive looseness?

Answer: Worn steering rack internal gear mesh allowing free movement at highway speeds

Rack and pinion gear mesh wear creates free play in the steering. At low speeds, tires are loaded against curbs or require turning force that masks the play. At highway speed on a straight road with minimal steering load, the free play in the gear mesh becomes noticeable as vague, imprecise steering feel.