How do you check the power steering on a 1.2 vauxhall corsa?

CORSA ELECTRIC POWER STEERING

There are some common faults with the Corsa Electric Power Steering

that manifest themselves as one or both of these conditions

1: The car pulls to one side or is easier turn in one direction when

all else seems to be correct. E.g. Tyres equal, steering and

suspension geometry good, brakes and wheel bearings good, driven on

a straight and level road.

2: When turning, the steering will randomly seem to jam or stick for

an instant, and the steering wheel becomes suddenly heavy and then

reverts to normal.

Both of these can be rectified using a few commonly available tools

and less than an hour's work. By many accounts the solution from your

friendly Vauxhall Opel dealer is to replace the entire column.

FAULT DESCRIPTION

The most common problem by far with the Corsa EPS is caused by the

torque sensing mechanical components wearing with age leading to an

error with the torque sensor reading that gradually gets worse. The

situation can be rectified by adjusting the position of the torque

sensor to a new zero position.

1: Steering pulls or has a preference for one direction

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This fault is caused by the mechanical components that translate the

steering column effort (Control Demand) into motion that is

proportional to torque. Direction is inferred by the magnitude of the

torque being positive or negative. This mechanical translation is

managed using a slant-pivot coupling connecting the upper and lower

parts of the steering column that operates a sliding collar normally

held in a central position by springs. The motion of the slant-pivot

coupling is limited, and at either extreme allows direct coupling

between the upper and lower sections of the steering column. The

torque sensor detects the position of the sliding collar and produces

an electrical signal to represent the effort and direction of turning

the steering wheel. The EPS system then activates the motor that

drives the lower section of the steering column in the correct

direction to reduce the sensor reading to zero. i.e. No more turning

is demanded.

The problem occurs when the slant-pivot coupling or the sliding

collar bind or lock at some position in the travel. The components

are lubricated when built, but the lubricant degrades over time and

eventually hardens and dries where it is thinnest. When the steering

is turned slowly or by a small amount the friction at some points is

enough to make the coupling bind rather than slide, causing a zero

torque reading that effectively removes all power assistance until

the coupling moves. To the driver this seems like the steering just

got very heavy or jammed for an instant.

It is possible to reinvigorate the assembly using a mixture of

ordinary gear oil and a molybdenum disulphide based additive such as

molyslip or stop smoke.

Method:

Carry out the same procedure as case 1, then mark the correct

position of the torque sensor and remove it.

Inject no more than 15cc of the Oil & MoS2 lubricant mixture into the

void around the sliding collar and replace the torque sensor

carefully. It will be necessary to rotate the sensor until the sensor

actuator engages with the sliding collar correctly. Until the sensor

is correctly engaged it will fail to seat properly. Do not force it

into place or use the screws to try and pull it into position. The

sensor arm is biased to one end by a spring and it will have moved

when the sensor was extracted. Offer it into place and feel for the

situation where the sensor arm spring tension can be detected. When

it is in the right position it will just go into place easily and

then it can be rotated to the correct neutral position as previously

marked.

Before replacing everything else, start the engine and check that the

steering behaves properly. If it turns in one direction switch off

immediately and reset the torque sensor position by following the

procedure for case 1.

After lubricating the internal components, a few days may need to

elapse before the lubricant penetrates all parts of the coupling.

Over this time the steering will gradually become lighter and may

start to favour one direction as the coupling finds a new equilibrium

position. If this occurs it will be necessary to reset the torque

sensor position again.