My power steering when out on my 91 Accord EX. For about a month it was intermittent, but now its out. How do I diagnose if it is the pump, the rack, or other?
Fluid is full, and there are no leaks and the belt is tight.

 

The pump, if defective, will usually be making some sort of noise, whether it be from air in the system, bad bearings or worn internal pump veins, but not always. Chances are its the pump. If you had intermittent power steering before than that makes most sense really but it isn't a definite. Were you getting any kind of noise from the pump prior to it failing completely? When you say it was working intermittently, what sort of symptoms were associated with the system? Sometimes the pressure relief valve that is designed to bypass the pumps output pressure away from the rack can stick or fail and render an otherwise functional pump, useless as well. It is difficult to diagnose without special gauges and fittings to check outlet pressure at different points in the system but you can try a few things.

• With engine at idle, slightly bump the steering wheel from side to side to apply changing loads to the pump, listen for changes in engine rpm and changes in noises from the pump itself. (A pump that, when steering input is applied, has no effect on engine rpm, indicates that there is no flow through the pump or high pressure being created for output to the rack) Also try turning the wheel all the way, in one direction, against the steering lock and listen again for the pressure changes at the pump such as the pressure relief valve. (A pump that makes no change in audible sound when at full-lock may have no output pressure)
• Check for leaks at the pump (Pump cover, high pressure output and low pressure pickup fittings/lines)
• Check for play in the rack and check for leaks at the rack. This would include the fittings for both the high pressure input and low pressure return. Play can be found between the internal rack rod-to-rack rod bushings and rack body. You can shake the wheel back and forth with the engine off and listen for clunking from the rack. Try doing this while placing a hand on the rack boots to see if the rack rod bushings have failed, if so then the seals have likely failed as well. A good way to check is to loosen the clamp for the rack boots and see if power steering fluid has accumulated inside the boots.