* Low Power Steering Fluid: Even after a pump replacement, it's crucial to check and top off the power steering fluid. Air in the system is a common cause of inconsistent assist, especially favoring one side. Make sure the fluid level is correct and bleed the system properly. There might be an air bubble trapped, especially if you didn't fully bleed the system after the pump replacement.
* Air in the Power Steering System: This is the most likely culprit given your symptoms. Air pockets interfere with the hydraulic pressure needed for proper assist. Improper bleeding or a leak somewhere in the system can introduce air. Look for leaks at all connections, hoses, and the pump itself.
* Power Steering Fluid Leaks: Even a small leak can cause problems. Carefully inspect all hoses, connections, and the pump itself for any signs of leakage. A slow leak could be depleting the fluid and introducing air.
* Pressure Switch or Sensor Issue (Less Likely): A faulty pressure sensor or switch could be providing incorrect readings to the system, leading to inconsistent assist. This is less likely given the RPM dependency.
* Problem with the Steering Gear Box (Less Likely): While less probable given your symptoms, a problem within the steering gear itself (internal seals, valve, etc.) could also contribute. This is more likely to cause issues across the steering range, not just a unilateral problem at low RPM.
Troubleshooting Steps:
1. Check and Top Off Power Steering Fluid: This is the first and easiest step. Use the correct type of power steering fluid for your truck (consult your owner's manual).
2. Bleed the Power Steering System: There are different methods to bleed a power steering system. Consult a repair manual specific to your 1999 Chevy 4x4 for the proper procedure. This usually involves turning the steering wheel lock-to-lock while the engine is running and the fluid reservoir is full.
3. Inspect for Leaks: Carefully examine all hoses, connections, and the pump for any leaks. Look for wet spots, fluid drips, or any signs of fluid loss.
4. Check the Power Steering Belt: Ensure the power steering belt is properly tensioned and not slipping. A slipping belt can reduce the pump's effectiveness.
If you've performed these steps and the problem persists, you may need to seek professional help from a mechanic. They have the tools and expertise to diagnose more complex issues, such as a faulty pressure switch or a problem with the steering gear box. They can also definitively rule out any internal issues within the new power steering pump.
