Auto Service World
Feature   April 1, 2004   by CARS Magazine

Power to the People

Two simple tips for better power steering service

Check for check valves

On many vehicles, starting over twenty years ago, check valves were introduced into the pressure side of their power steering system. The purpose of the valves is to maintain back pressure against the pump and prevent back pressure surges.

Check valves can be found in two locations. In some applications using his valve, it is housed in a threaded fitting between the gear and the pressure hose (see Figure 2). Other applications using a check valve have a cavity machined in the steering gear (See Figure 3).


If the gear is rotated during removal from a confined space, it is possible for the valve to fall out. If the valve is dislodged from its seat, replace as shown in the illustrations.

Service Tips:

If the vehicle is equipped with a check valve, make sure that any replacement also has the valve.

If the valve is in the gear housing cavity, it can be easily seen after power steering hose removal (See Figure 4).

Over tightening of the pressure hose can damage the valve.

Failure to reinstall this valve will affect steering operation.

System Flushing after Power Steering Component Replacement

Even normal component wear will introduce contaminants into a power steering system. These contaminants will circulate throughout the system, with some acting as cutting agents eventually causing seal failure.

Flushing should be performed whenever power steering system components are replaced. Flushing is the only way to ensure that all contaminants are removed from the system.

There are dedicated machines designed for fast and easy power steering system flushing, but if you don’t have a machine, it’s still possible to flush many conventional power steering systems through their pressure and return lines (See diagrams).

What about inline filters? There’re an excellent idea, but they can’t replace system flushing, for two reasons. The first is that the screen size of inline filters can’t trap the smaller particles which can cause accelerated wear and secondly, they’re designed to bypass fluid. The bypass is designed to prevent the system from locking up should the filter become clogged. What’s the best procedure? Flush, and install a filter. And remember the filter goes on the return side of the system.

Thanks to Moog/Federal Mogul Corp.

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