310S Steering and Suspension 3 — Questions and Answers
Question 1: What type of power steering system uses an electric motor instead of a hydraulic pump?
- Hydraulic assist power steering
- Electric power steering (EPS) (Correct answer)
- Electrohydraulic power steering
- Variable-ratio power steering
Correct answer: Electric power steering (EPS)
Electric power steering (EPS) uses an electric motor mounted on the steering column or rack to provide steering assist. It eliminates the hydraulic pump, hoses, and fluid, improving fuel efficiency and enabling advanced driver-assist features.
Question 2: What does a worn outer tie rod end typically cause?
- A pull to one side during acceleration
- Loose steering feel, wandering, and accelerated toe-related tire wear (Correct answer)
- Excessive body roll during cornering
- A vibration felt through the brake pedal
Correct answer: Loose steering feel, wandering, and accelerated toe-related tire wear
A worn outer tie rod end introduces play in the steering linkage, causing loose steering, wandering at highway speeds, and loss of proper toe alignment, leading to feathered or scuffed tire wear patterns.
Question 3: When performing a ball joint inspection, what indicates a worn load-carrying ball joint on a short-long arm (SLA) suspension?
- Excessive play detected when the suspension is loaded (wheels on the ground)
- Excessive axial (vertical) play measured with the suspension unloaded (wheel raised off the ground) using a dial indicator (Correct answer)
- Torn dust boot only
- Noise only when turning
Correct answer: Excessive axial (vertical) play measured with the suspension unloaded (wheel raised off the ground) using a dial indicator
Load-carrying ball joints must be unloaded for inspection. On an SLA suspension, the lower ball joint typically carries the load, so the wheel is raised and a dial indicator measures vertical play at the joint.
Question 4: What is the purpose of the power steering pressure switch?
- To regulate maximum steering pump pressure
- To signal the ECM to increase idle speed when steering load is high to prevent stalling (Correct answer)
- To activate the power steering warning light
- To control the flow control valve in the pump
Correct answer: To signal the ECM to increase idle speed when steering load is high to prevent stalling
When the power steering system is under high load (such as during parking manoeuvres), the pressure switch signals the ECM to increase idle speed, compensating for the additional load on the engine from the power steering pump.
Question 5: What causes cupping (scalloped wear) on tires?
- Driving on underinflated tires
- Worn shock absorbers or struts allowing the tire to bounce and lose contact with the road (Correct answer)
- Excessive positive toe setting
- Driving with the parking brake engaged
Correct answer: Worn shock absorbers or struts allowing the tire to bounce and lose contact with the road
Cupping occurs when worn dampers (shock absorbers or struts) fail to keep the tire in consistent contact with the road. The tire bounces, creating a pattern of high and low spots around the tread surface.
Question 6: What is the function of the upper strut mount (bearing plate)?
- To attach the brake caliper to the knuckle
- To allow the strut assembly to pivot when the steering wheel is turned while isolating suspension noise from the body (Correct answer)
- To support the engine weight
- To connect the stabilizer bar to the strut
Correct answer: To allow the strut assembly to pivot when the steering wheel is turned while isolating suspension noise from the body
The upper strut mount attaches the strut to the body and contains a bearing that allows the strut to rotate when steering. It also includes rubber isolation to prevent road noise and vibration from transferring to the body.
310S Steering and Suspension 3
What type of power steering system uses an electric motor instead of a hydraulic pump?