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What exactly do Power Steering Pumps do?

The Power steering system in your car (also known as power assisted steering (PAS) or steering assist system) helps you steer without a large amount of effort at the steering wheel. Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only modest effort regardless of conditions. Power steering helps considerably when a vehicle is stopped or moving slowly. Also, power steering provides some feedback of forces acting on the front wheels to give an ongoing sense of how the wheels are interacting with the road; this is typically called “r?ad feel”.

Representative power steering systems for cars augment steering effort via an actuator, a hydraulic cylinder, which is part of a servo system. These systems have a direct mechanical connection between the steering wheel and the linkage that steers the wheels. This means that power-steering system failure (to augment effort) still permits the vehicle to be steered using manual effort alone.

Other power steering systems (such as those in the largest off-road construction vehicles) have no direct mechanical connection to the steering linkage; they require electrical power. Systems of this kind, with no mechanical connection, are sometimes called “drive by wire” or “steer by wire”, by analogy with aviation’s “fly-by-wire”. In this context, “wire” refers to electrical cables that carry power and data, not thin-wire-rope mechanical control cables.

In other power steering systems, electric motors provide the assistance instead of hydraulic systems. As with hydraulic types, power to the actuator (motor, in this case) is controlled by the rest of the power-steering system.

Some construction vehicles have a two-part frame with a rugged hinge in the middle; this hinge allows the front and rear axles to become non-parallel to steer the vehicle. Opposing hydraulic cylinders move the halves of the frame relative to each other to steer.

Most power steering systems work by using a hydraulic system to multiply force applied to the steering wheel inputs to the vehicle’s steered (usually front) road wheels.[11] The hydraulic pressure typically comes from a gerotor or rotary vane pump driven by the vehicle’s engine. A double-acting hydraulic cylinder applies a force to the steering gear, which in turn steers the roadwheels. The steering wheel operates valves to control flow to the cylinder. The more torque the driver applies to the steering wheel and column, the more fluid the valves allow through to the cylinder, and so the more force is applied to steer the wheels.[12]

One design for measuring the torque applied to the steering wheel has a torque sensor – a torsion bar at the lower end of the steering column. As the steering wheel rotates, so does the steering column, as well as the upper end of the torsion bar. Since the torsion bar is relatively thin and flexible, and the bottom end usually resists being rotated, the bar will twist by an amount proportional to the applied torque. The difference in position between the opposite ends of the torsion bar controls a valve. The valve allows fluid to flow to the cylinder which provides steering assistance; the greater the “twist” of the torsion bar, the greater the force.

Since the hydraulic pumps are positive-displacement type, the flow rate they deliver is directly proportional to the speed of the engine. This means that at high engine speeds the steering would naturally operate faster than at low engine speeds. Because this would be undesirable, a restricting orifice and flow-control valve direct some of the pump’s output back to the hydraulic reservoir at high engine speeds. A pressure relief valve prevents a dangerous build-up of pressure when the hydraulic cylinder’s piston reaches the end of its stroke.

The steering booster is arranged so that should the booster fail, the steering will continue to work (although the wheel will feel heavier). Loss of power steering can significantly affect the handling of a vehicle. Each vehicle owner’s manual gives instructions for inspection of fluid levels and regular maintenance of the power steering system.

The working liquid, also called “hydraulic fluid” or “oil”, is the medium by which pressure is transmitted. Common working liquids are based on mineral oil. Some modern systems also include an electronic control valve to reduce the hydraulic supply pressure as the vehicle’s speed increases; this is variable-assist power steering.

source: wikipedia

SRS Warning Light! What you need to know…it’s a safety issue..

Have you ever had that annoying light illuminated at your instrument cluster and wondered what it meant?

The SRS warning light refers to the Supplemental Restraint System (SRS) and is most commonly known as the airbag system light. This is a computer controlled system designed to deploy one or more driver, passenger, and side airbags. The computer also tightens the seat belts to protect the vehicle occupants from physical harm during an impact caused by a collision.

The SRS system is also referred to as a passive restraint system because the vehicle occupants do not need to do anything in order to activate the SRS system when the enabling criteria—speed and deceleration—are met. In contrast, seat belts are an active restraint system. The vehicle occupants must proactively latch each seat belt in order for the seat belt to do its job. Even automatic seat belt systems have a lap belt that must be manually latched.

The Bulb Check: SRS Warning Light

When the vehicle is first started, the SRS light should illuminate for 1 to 5 seconds while the system goes through a self-test sequence. If the light goes out, then the system is ready. If the light stays on, there is a fault somewhere in the SRS system. The system is disabled at this point. In the case of a collision, the airbags will not deploy and the seat belts will not tighten, nor will any additional features activate.

What to Do: SRS Warning Light

If the SRS light stays on after the self-test, then you should take the vehicle to a qualified repair shop to be properly diagnosed and inspected. It is a good idea to check your vehicle’s potential manufacturer recalls because some airbag system repairs may be covered under recalls or extended warranties. Don’t delay—you may not be properly protected in the case of an accident or collision.

It is not commonly knows that the SRS system contains a “black box” very much like a commercial airplane. It not only records the data from an accident such as the speed, “G” forces, how many seat belts were latched etc., but it also how long the SRS system was disabled due to a fault condition. If the insurance company determines that the SRS system was in a fault mode for what they consider to be a long time, they may not be willing to cover any injuries, especially if they determine that a working airbag system would have prevented the injuries.
If the SRS light is blinking or stays on, take it seriously. There is a fault condition and the vehicle’s safety systems are compromised, putting you and your passengers at risk.

Background Information: SRS Warning Light

The SRS computer system continuously evaluates the input data sent to it by motion or “G” sensors, vehicle speed sensors, steering system sensors, vehicle angle sensors, and seat belt sensors. When the enabling criteria have been met—such as a vehicle speed above 25 MPH and a highly abnormal rate of deceleration—the SRS system will choose which, if any, airbags to deploy and which seat belts to pull tight. The purpose of the airbags is to cushion or prevent the vehicle occupants from hitting and slamming their body parts, especially the head, into the steering wheel or dashboard. The seat belts tighten in order to restrict the forward movement of the vehicle occupants.

Newer, more enhanced SRS systems recline the front seat backs, lowering the driver and passenger into a prone position to better absorb the whiplash/recoil phase of a collision and hopefully prevent any neck or spinal injury. Many newer vehicles have side airbags to protect the vehicle occupants from hitting the side pillars, especially with their heads. Some new vehicles also have SRS curtains that come down to protect the occupants from breaking glass from windshields and windows.

Source:  Wikipedia

What Client Say

As a former sales rep in the automotive industry, I’ve had the opportunity to visit over a thousand workshops between Brisbane and Bundaberg, including all of the major prestige dealerships. The SVS Autocare workshop is one of the most pristine …

Michael Lane

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The service provided by SVS Autocare is secondary to none. All their staff are friendly, efficient and knowledgeable. They send regular reminders. They pick up our cars from work and drop them back before the end of the day or …

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