Wheel bearings

The wheel bearings are situated inside the wheel hub. The wheel bearings allow the wheels to turn with little friction. The hub usually has two bearings an inner and an outer one. Another crucial part of the wheel assembly is the seals to protect the bearings from dirt and any other foreign matter that may damage the bearings. The bearings are covered with lithium grease for lubricating purposes and because it can handle the heat created by the bearings and the brakes. If there is no grease/little on the bearings it will cause the bearings to create a lot of heat as the wheel turns, the bearings will expand because of this and seize. Once the bearings cool down they may be able to turn again but the will be damaged and will need to be replaced. A damaged wheel bearing can affect the vehicles handling/operation and the passengers' safety.

We pulled a wheel hub apart and cleaned it with brake cleaner. We found that the inner bearing's outer race had marks on it. In this case the hub would be fitted with a new bearing kit (inner bearing, outer bearing, lithium grease and new seals). If one bearing is damaged it is best to get a bearing kit as the other bearing may wear out soon after. When re-assembling the wheel hub it is important that the adjustment nut is not over tightened as this will put a lot of force on the bearings and it can cause them to wear out faster or even cause it to seize. It is also important to make sure that the grease cap and the grease retainer seal properly.

Steering rack

The steering rack is used to convert the steering wheel's rotational motion into a linear motion to change the direction of the wheels. The steering rack uses a rack and pinion gear set to convert the rotational motion it also uses a specific gear ratio to make it easier to turn the steering wheel. The rack also has a piston attached to it with fluid port on both sides of it on the cylinder surrounding the piston. The steering rack has a rotary valve where the steering column connects to the rack, the rotary valve opens and allows high pressure fluid to go to the steering rack piston. The fluid pushes against the piston when the steering wheel is turned to assist the driver when the vehicle is travelling at low speeds.

When servicing a steering rack it is important to fit the rack new seals when assembling it, to prevent the power steering fluid from leaking and to prevent dust and dirt from getting into the moving parts as it will wear it out faster. It is also important to check the play/clearance on the tie rod to rack connection and in the tie rod end ball joints. If there is too much play it may affect the vehicles toe and the vehicle's steering. The vehicle's play on the steering is caused by the clearance between the rack and pinion gears. The play between the gears is adjusted by a bolt that is connected to a nylon yoke, if the bolt is tightened the yoke pushes the rack closer to the pinion gear and when it is loosened the clearance is increased.

 Checking the run out on the rack gear 

Power Steering Pump

The power steering pump is used to assist the driver to steer the vehicle at low speeds. The is powered by the fan belt, it has a similar design as an oil pump. It uses a rotor with vanes on it inside a cam ring to pump the power steering fluid to the steering rack. The pump has a high pressure hose that goes to the steering rack and a low pressure hose that returns the fluid from the steering rack. The pump has a pressure relief valve to let the fluid return to the reservoir when the car is traveling at high speeds.

The main problems that occur in steering pumps is that the fluid lines break or the seals wear out so the pump loses fluid. The bearings also wear out due to its age or the fan belt is over tightened. Most power steering pump pulleys are bolted on to the pump shaft although some are pressed on. To get a pulley off that has been pressed on the pulley needs to be heated up so that it expands and then pulled off with a puller.

Wheel Alignment

Pre-checks

• Jack the car up or lift it up with the hoist. Check the tie rod ends with the wheels on the hoist, have someone sit in the driver seat and turn the steering wheel from left to right vigorously. If a clicking sound is heard when checking the tie rod ends it means they are worn, It could also be checked visually or by feeling it with your hand
• Check the ball joint, bushes and the wheel bearing by raising the vehicle and pushing the wheel from side to side and up and down. If the wheel has play the faulty parts need to be replaced or repaired.
• The tire pressures should be checked and pumped up to the correct pressure

Setting up 

• Make sure that the turn tables are locked
• If the car was raised on the hoist it should be pushed off and back on to reset the suspension joints
• The hoist should be locked into the first pin to make sure that the car is level 
• Once the car is on the hoist and in place the turn table locks should be removed

The car is now ready for the wheel alignment machine

The only thing that could be adjusted on the car that we were working on was the toe because it is a front wheel drive car. Things like the caster, camber, steering axis inclination, included angle etc. Can generally not be adjusted on a front wheel drive vehicle

Adjusting the toe on the tie rod