Power steering pumps don't typically fail intermittently, then work again. There are some that get weak and don't produce enough pressure at idle. There can also be internal leakage in the spool valve of rack and pinion steering gears. That will cause intermittent power assist when the fluid is still cold, but it almost always affects turning in only one direction first, then the other direction weeks later. For what you described I would suspect the drive belt for the pump is slipping. If your engine uses a spring-loaded tensioner pulley, check that to be sure it's not rusted tight and that it is holding sufficient tension on the belt. Have a helper turn the steering wheel back and forth with the engine running while you dribble a little water on the belt.
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Saturday, March 2nd, 2013 AT 2:31 AM