Sounds like a weak pump. To prove it, simply raise engine speed a few hundred rpm. If the power assist comes back, replace the pump. That is more common on the "ZF" style pump which is a small square unit with a remote-mounted reservoir. When it isn't moving fluid, turning the steering wheel often results in you pushing fluid from the rack and pinion into the reservoir. It overflows because no fluid is being pushed back into the rack. That overflowing is a secondary clue / observation, not a problem in itself.
If the power assist is better one way than the other, suspect internal leakage in the rack and pinion assembly. The assist will come back after a few minutes when the fluid and teflon seals warm up. GM had a really huge problem with that in the their front-wheel-drive cars in the '90s. Their cobble-job repair was designed to get the car through the 50,000 mile warranty so the customer would have to pay for the proper repair. The proper repair for internal leakage is to replace the rack and pinion assembly. Have your mechanic install a name brand rebuilt unit such as Moog or Federal Mogul. (They probably will on their own). Those companies came up with a permanent solution to GM's problem and they incorporate that into all the racks they remanufacture.
Monday, April 11th, 2011 AT 7:43 PM