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Discussion Starter #1
I've got a 2011 STI hatch with about 117k on it. I feel like i've always had PS noise but it seems to be worse now. Maybe three years ago i noticed that there appeared to be a slight PS leak under the car, which I determined was most likely the pinion valve seal leaking, but interestingly enough it isn't that bad and doesnt affect my fluid level at all. Recently, i upgraded all the spring clamps in the system to worm drive clamps, replaced the o-ring on the pump with an OEM o-ring (the correct part), and flushed the system and bled as best as i could.

Since doing all of this i eliminated a slight PS noise when turning just after starting the car cold. That is completely gone now, however i notice once the car is sufficiently warmed up if i rev the car up to 2,000rpm (in gear or in neutral) and just slightly turn the wheels in either direction, the pump will start to whine and will continue until about 3,000rpm, when it stops. the noise pitch increases with engine speed and i am certain it is the pump making noise. Overall, my steering feels normal although it does sometimes hesitate just slightly when i'm in that engine speed range and can hear the whine. If i hear that noise and turn off the car, checking the reservoir reveals foaming, so there is definitely air in the system coming from somewhere.

I've removed the belt from the pump and spun it by hand; feels smooth, very little play on the shaft. The pump itself (nor frankly, the entire system other than the pinion valve) does not leak (i almost never have to top off the reservoir unless i am replacing the fluid). I've considered replacing the rack or pinion valve but honestly the leak is minimal, if anything. I figured maybe the pump is bad but it doesnt leak and the shaft and bearings look to be in working order. The lines themselves are still soft (California car, bay area doesnt get too hot or cold and no snow) so I dont see a need to replace it.

I guess my question is whether air could be entering the system through that pinion valve seal. Maybe the movement of the rack is creating a vacuum that is pulling air through the valve, but I've heard that air usually enters the system through the low pressure suction side, which i've tried to remedy with new clamps and an o-ring. Any ideas?
 

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Discussion Starter #2
So I jacked up the front of the car and started it up to try to bleed some air out of the system. With the car running I went ahead and starting turning the wheel from lock to lock, slowly. Immediately the steering wheels and wheel began violently shuddering. I could get the shuddering to stop if i pushed the wheel to lock (I'm guessing there is some relief valve activated at that point), but the shuddering will begin again one you start moving the wheel again. The reservoir will start to overflow and is entirely foamed up with air. i tried letting the air in the reservoir gas off and then turn the wheels back and forth with the engine off until no more bubbles formed, but when i start the car again (wheels still off the ground), the wheels start shuddering again. Turning it back and forth produces even more foam and the pump is groaning like crazy.

I think i am going to replace the pump. The o-ring fix did nothing, a fluid flush did nothing, and adding worm gear clamps to the lines likewise did nothing. There are no apparent leaks at least on the top of the engine (the rack is slightly leaking from the valve but never enough to cause even a drip on my garage floor or diminish the fluid in the reservoir), but obviously the system is getting air from somewhere. The car is non-functional because of this, granted it has 117k miles on it.

Should I just replace the pump? If so, should I go OEM or remanufactured?
 

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Discussion Starter #4
Yeah, that is what I am thinking too. I pulled the pump yesterday and took it apart, and all the components, rotor, vane, etc. are all in good condition (i dont imagine these parts wear at all). I will try to source some new seals for it and reassemble it, or just replace it (though I am hoping to avoid $400 for a new pump).

I noticed the rack had a slight leak as many as 70,000 miles ago. Perhaps by now the whole thing is just toast. Do you think the rack is most likely the source of air at this point?
 

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The steering rack leak issue on our STIs is more common than rod knock or piston ring failures. It's very very common.

It might interest you to know that you can install a 2015 STI steering rack instead if you're going to replace your existing rack. The 2015 STI rack has a quicker ratio and makes a huge difference in driveability.

See my findings in this thread:

Swap a 2015+ Rack into an earlier STI?**** Parts Update Post 1 ****
 

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Had the same issue on my 2011 STI before I sold it, around 120,000km's - I had extended warranty so it was fully covered but the cost was something like $1300 total for the repair, wasn't cheap! As nox said it's about $850-950CAD to buy a 2015 steering rack plus install (save on install if you do it yourself!) good luck!
 

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Discussion Starter #7
Thanks for the replies. I ordered a new 2015 OEM rack and will be installing it Tuesday. I already pulled the old rack and it was pretty wet, so for lack of leaks anywhere else in the system I suspect that was the source of air in the system/malfunction. I also rebuilt the pump (i can provide a list of all the o-rings you need for ps pumps for an 08+ STi if anyone is interested) and replaced the suction hose line, plastic low pressure connector to the top of the ps pump, and the o-ring and metal gasket for the low/hi pressure attachments. I will follow up once everything is installed.
 

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Discussion Starter #8
Well, the install went well other than stripping a nut welded to the chassis (helicoil worked very well). The pump I rebuilt seems to be working well and the noise is much quieter now. I imagine it will dissipate further once all the air is worked out of the system.

Maybe I'm not used to it but the steering definitely feels much stiffer. I figure that's the result of a quicker rack, but am also concerned that it could be something else, maybe i over tightened the steering column u joint where it attaches to the rack splines? Seems unlikely.

Also, since I did the install I've noticed a strange stumble at about 2500rpm. Didnt do that before. I'll check all my vacuum lines but didnt really touch anything other than the ps system. My car was pro tuned several years ago and never exhibited that problem. Cant see how it is related to this but awfully coincidental.
 

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Discussion Starter #10
Thanks. I haven't had a chance to drive it anywhere interesting yet but I do like the lack of play in the center compared to the old rack. Just got it aligned today so I'll put some miles on it this weekend.
 
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