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Article > Chassis (Suspension/Steering)

Electric Power-Assisted Steering Makes Inroads


4/4/2013
By Larry Carley

Depending on usage and mileage, a power steering pump's shaft bearings or pump mechanism can wear out.
 
Hydraulic power steering has been standard equipment on most cars and trucks for many decades, but on many newer vehicles it is being replaced by electric power-assisted steering. Electric steering assist eliminates the belt-driven PS pump, hoses and hydraulic fluid to reduce weight, noise and friction. The change also improves fuel economy and allows steering effort and feel to be better tuned to changing driving conditions. But even if hydraulic power steering disappears entirely, there will continue to be a huge aftermarket for replacement PS pumps, hoses and related components.

PS pumps are fairly durable and often last the life of the vehicle. However, depending on usage and mileage, the pump’s shaft bearings and/or pump mechanism can wear out, causing pump noise and/or a loss of steering assist. The pump’s pressure relief valve can also stuck or fail causing a loss of power steering assist.

When a PS pump fails as a result of wear or internal damage, metallic debris may pass through the hydraulic lines and damage the power steering unit. Consequently, when a PS pump is being replaced all of the old fluid should be drained from the system and discarded. The hoses and steering gear also should be flushed to remove the contaminants. If this is not done, the new pump may be damaged.

Replacement pumps may or may not come with a pulley. If not, the pulley on the old pump must be removed and installed on the new pump. DIY installers should be warned NOT to pound on the pulley or pump shaft as this may damage the pump.

The PS system should be refilled with the type of fluid specified on the pump reservoir or in the vehicle owners manual. Most vehicles can use a universal PS fluid, but some require special fluids or ATF. Using the wrong fluid may damage the pump or steering unit.

Refilling some PS systems can be tricky because air can become trapped in the steering gear. Air will cause noise and erratic steering assist. Rotating the steering wheel slowly from as far as it will go in one direction to its limit in the opposite direction multiple times will usually allow most of the air to escape. In some cases, it may be necessary to use a special vacuum tool to pull the remaining air out of the system.
A new drive belt should also be installed when a high-mileage PS pump is replaced. Chances are the old belt will have a lot of miles on it and will be badly worn, glazed or contaminated with oil, grease or PS fluid that leaked out of the old pump. The automatic belt tensioner also should be carefully inspected and replaced if it is sticking, rusty, wobbling, noisy or can’t maintain proper belt tension. 












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