Duplicate Post from C6 forum. Hoping you guys can help

So, I replaced my power steering pump. At first the steering worked fine at idle and under normal driving. But if I get on the throttle and let off the throttle I lose power steering. If I let the car idle in neutral, then turn the wheel back and forth I feel it reengage. and it works fine until I drive the car hard again. It acts like one of the valves in the system is sticking. The system worked fine before the pump change. So it makes me think the relief valve in the pump is sticking open when I pour the coals to it.
Can anyone offer any advice for diagnostics. Could this be an air bubble in in the system. I feel like I drove it and turned the wheel back and forth enough to bleed it. Maybe that's not the right bleed procedure. I did hand prime the pump before installing the belt
Thanks for any help

 

This is the FSM PS Bleed Procedure for the C6:

Power Steering System Bleeding
Important: Power steering fluid level must be maintained throughout bleed procedure.
1. Fill pump reservoir with fluid to minimum system level, FULL COLD level, or middle of hash mark on cap stick fluid level indicator.
2. Raise the vehicle until the front wheels are off the ground.
3. Key on engine OFF, turn the steering wheel from stop to stop 12 times.
4. Verify power steering fluid level per operating specification.
5. Start the engine. Rotate steering wheel from left to right. Check for sign of cavitation or fluid aeration (pump noise/whining).
6. Verify the fluid level. Repeat the bleed procedure, if necessary.

If bleeding doesn't help then you may need to flush the system:

Power Steering System Flushing
Important: Do not reuse any drained power steering fluid regardless of appearance or condition.

Turn OFF the engine.
Raise the front end of the vehicle off the ground until the tires and wheels turn freely. Refer to Lifting and Jacking the Vehicle.
Place a large container under the fluid return hose in order to collect the draining fluid.
Remove the fluid return hose at the power steering pump reservoir inlet connection.
Plug the reservoir return hose inlet connection on the power steering pump.
Important: This step may require 4 L (4 qt) of power steering fluid until the draining fluid appears clear.

With the key on engine off, turn the steering wheel fully to the left and to the right while an assistant maintains the minimum fluid level in the reservoir using new approved power steering fluid. Continue until the fluid from the return hose runs clear.
Remove the plug from the pump reservoir inlet connection and install the fluid return hose to the pump reservoir.
Important: Do NOT run the engine without the power steering fluid at a minimum system level.

Bleed the power steering system. Refer to Power Steering System Bleeding.
Inspect the power steering fluid for the following indications of contamination:
• Milky fluid - water
• Brown fluid - burnt
• Plastic debris or dirt chunks

If the fluid is contaminated, repeat steps 2-9.
Lower the vehicle and check the Power Steering system for leaks.

Hope this helps. If not then it probably is something wrong with the pump itself since that is the only thing you changed although debris from a failed pump can take down the rack as well. The dealership more than likely has a tool that can test the performance of the pump but I doubt you have one. It is listed here:
https://www.ebay.com/p/Kent-Moore-J-...Cs24/665967058

Bill

 

Thanks Bill.
I should have mentioned why I changed the pump. One of the long M8-1.25 bolts holding the pump to the alternator bracket broke off. It didn't do any damage to the pump. It still worked as it should. But it broke the part of the housing that captures the bolt. So, I'm afraid I may have a faulty remanufactured pump. Before I take it back off, I want to do as much diagnostics as I can in case the pump is ok.

 

Give us a call on Monday and talk with Jeff. He will be able to help solve your issue.

Thanks,
Junior

 

Many quotes by Bill there of "engine OFF". I'm just a diy guy but never did it that way. I always filled more then min. Front Wheels off ground. Start engine. Check fluid level cold filled to middle hot/cold. Turn wheel lock to lock a dozen times motor on which IMO only way to cycle fluid and make system work. Wheels down. Then let fluid cool and measure cold level and that's it. In my time I've replaced maybe a dozen racks Toyotas to vettes to ferraris. All the same.

With engine off I don't see you you can get air out of system. It is the pump that pushes the fluid and the pump has to move to fill the pump from the reservoir. If Bill's list is the GM way...oh well I'm just a hillbilly.

 

I always do it engine off first... can't stand that initial 'empty pump, I'm gonna explode' sound.
But I agree, can't get all the air out without the pump running. Must be just a hillbilly too...

 

I have seen too many helpful posts by Bill so I didn't question his advice. I did just as he suggested and the problem is fixed.

Although I agree it seems the pump should be running, the steering box is pushing the fluid, not the pump. The pump only gives it the power to make it easy. The pump instructions said to hand prime it and i did. So this process proves that the fluid free flows thru the pump when the pump is off. I may be wrong about all this, but the problem is repaired. Thanks to all.
The concern about starting the engine is the pump may hit an air trap and then burn the vanes (the pump is a rotary vane pump) out before the pump gets good oil.