Mercedes-Benz S420 Power Steering Pump Replacement Cost

Power steering pumps create hydraulic pressure, and a hose transfers the pressure to the steering gear, where it can be used to assist in turning the wheels. Another hose then returns the used fluid to be pressurized. This process happens continuously, and the power steering pump pressurizes fluid any time the engine is running.

If you have a power steering fluid leak, you'll likely see a puddle of it on the ground under your car. If the fluid level gets too low, the car will get harder to steer, especially at low speeds. The power steering pump may also start making a screeching noise when you turn the steering wheel. » MORE: Signs your power steering pump is going bad

A vehicle can be driven with leaking power steering components, but you'll need to make sure there's enough fluid for the system to function. If the fluid is leaking fast, have the car towed to a repair shop to prevent damage to the power steering system.

In most vehicles, the power steering system will last well over 100,000 miles before any failures occur. Mechanical issues and leaks in the power steering system are usually avoidable if you stick to the maintenance schedule in your owner's manual. But because of the pressure in the system, parts of it will eventually wear out.

Most power steering issues will create the same symptoms, so it can be difficult to diagnose one part without examining the whole system. When symptoms emerge, the power steering fluid is inspected and topped off, and the condition and tension of the power steering pump belt is noted. The system may need to be bled of air before diagnosis. Any leaks will become very obvious at that time, and noise from the pump would indicated that it has failed mechanically.

To replace the pump, the power steering fluid will first need to be drained. The serpentine or power steering belt will be removed, the hoses will be taken off, and the pump will be unbolted from the engine block. A new pump will then be installed, the lines attached, the belt reinstalled, and the fluid refilled. The system will be bled of air and checked to ensure a complete repair.

When having the power steering pump replaced, the power steering fluid hoses and related components should be inspected. Any debris from the pump may have worked into the steering system, requiring replacement of the hoses, and at least a flushing of the steering rack or gearbox. It's also smart to replace the plastic fluid reservoir at the same time.

Power steering components are subject to high pressure, heat and speeds. Using parts that are built to meet or exceed OEM standards will help ensure the longevity of the system. Inferior parts tend to lead to repeated replacement.

Replacing a power steering pump can be a good repair for the advanced DIYer — but it involves a lot of work. You'll need to drain and refill the power steering system, and bleed the system to purge any trapped air. A torque wrench is usually necessary, as the brass washers must be tightened to specification to prevent leaks. If the power steering pump mounting bolts are integrated into other components, requiring extensive disassembly, consider letting a certified technician handle this job to prevent damage to the engine.