2006 benz high pressure hose we replaced the power steering pump three times and still hearing a whinning noise could this be the prolbem

no info generic answer was it bleed of air --correctly installed --fluid replaced correct level---possible rack or gear box failing

A whinning noise while turning is an indication of a worn bearing. The extra pressure put against the bearing/race during the turn and the closing of a gap creates this noise.I would chech the axle bearings on the side of the truck on the outside the curve when you hear it. What I'm saying is if you hear it when you turn left....check the right side bearing

Whinning Causes
The whining noise you hear coming from the power steering pump is one of three things. The first is more of a loud "hush" than a whine; this is the sound of fluid rushing through the bypass valve when you turn the wheel all the way to one side or the other. Sometimes the bypass valve malfunctions or doesn't open all the way, causing pressure to back up in the pump and cause your engine rpm to drop. The second and third causes result from cavitation -- vacuum pockets created behind the rotor's vane blades as a result of extremely high pump action -- or air in the lines.

I just finished replacing mine.

It is much easier if you do these steps:

1. Remove the serpentine belt.
2. Remove the nuts holding the main fuse box over the battery.
3. Remove the reinforcing bar over the battery.
4. Remove the battery.
5. Remove the windsheild washer tank.
6. Now you have access to remove the pump pulley. Without removing the stuff, it may be possible, but it will be extremely difficult.
7. Remove the pump pulley.
8. Loosen the high pressure hose fitting.
9. Remove the return line clamp.
10. Remove the power steering pump mounting bolts.
11. Remove the high pressure hose fitting.
12. Remove the power steering pump while sliding off the low pressure hose.
13. Remove the clips holding the reservoir on the pump.
14. Remove the reservoir.
15. Install new o-ring on the reservoir.
16. Install reservoir on new pump.
17. Install clips to hold reservoir on pump.
18. Install new o-ring on high pressure fitting.
19. Place new pump in position while sliding on low pressure hose.
20. Loosely attache high pressure fitting.
21. Tighten pump to mounts.
22. Tighten high pressure fitting.
23. Install clamp on low pressure hose.
24. Install power steering pulley.
25. Install washer reservoir.
26. Install battery.
27. Install reinforcing cross member.
28. Install fuse panel.
29. Install serpentine belt.
30. Bleed the power steering system.

are you sure the noise is comming from pump and not the belt tension pulley right next to it ?

I use a wiffle ball bat with both end caps cut off (hollow tube) held to my ear to help localize noises on running engines I have even found tricky intake vac leaks with that trick

you may need to replace your steering fluid. dirty steering fluid can cause to make your steering wheel hard to turn.

90% of the time the problem is not the pump, but the hose connections. Detach the connections, clean any debis on the threads and reattach. Be careful not to cross thread when reattaching and don't over-tighten. Making a connection too tight might warp the connection and cause a leak. In severe cases you may need to replace the hoses. They are available at most auto parts store and will save you $$ over going to a dealer.

the rack and pinion unit may have a pinhole leak

If the pump is low or empty, the most likely cause would be the high pressure hose is leaking and needs to be replaced. If the power steering reservoir is full and the pump is still making noise then it could be the pump or a restriction in the rack valve body.

Generally it should work it's way out by itself, but you can remove air by turning the wheels all the way in one direction (hold it there a few seconds) then repeat in other direction...check fluid level and that's all. If noise lasts more than a few hours, then pump has sustained some damage.