Power Steering Res Cap issue
 

What issues would not having the correct power steering reservoir cap create. If the cap is not totally tight i'm assuming air will get in the system which may be causing the steering shudder i have all of a sudden, it wasn't there before. The OEM cap was broken and i'm waiting on another. In the mean time i just have a cap that isn't totally tight but better than nothing......

Actually, the cap is vented (I can't recall where I read that... the owner's manual?), so I doubt that's the cause of your problem.

dcb

Its a bad power steering O-ring between the reservoir tank and the pump itself. This lets air into the system and causes the exact symptoms you describe.

A very easy fix. See the How-To document HERE

Air coming in from the cap cannot be the problem. Every time you take off the cap to check or add fluid, air gets in. The problem is air is getting into the fluid (past a bad O-ring) from the bottom of the fluid reservoir and into the pump itself.

O-ring is about $1.00 from Subaru.

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Should have added PS pump and o-ring replaced about 2 months ago. Power steering line clamp replaced yesterday after failure and releasing ATF all over the place. I wasn't happy at all since about a month ago a trans line clamp failed spewing ATF all over the place, so initially i thought that was the problem AGAIN but when i needed two arms to park the damn car i knew it was the PS THAT WAS SPEWING FLUID not the trans this time......
So it sounds like the PS reservoir cap isn't the issue. Could there be air in the system from reconnecting the PS line? Can you damage the PS Rack driving the car with out fluid. The only driving i actually did after the PS hose clamp failure was a few parking moves here and there.

Mant times, just starting the car turning the steering wheel from lock-to-lock several times is enough to release some of the air in the system.

You could also flush out the PS system to release trapped air. I am assuming you have new ATF in the system. The power steering flushing procedure can be found HERE

As long as there is fluid in the system creating pressure, your rack should be fine.
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After 2 days of riding and topping the reservoir off with ATF everything took care of itself. No more shudder at low speeds and actually the low speed steering is very light, much lighter than it has been the entire time i've owned the vehicle, which is going on 3 years, so it's working as advertised.........
Finally got a new PS reservoir cap today.....Took 5 days to arrive......

Just something people may not be aware of is that Home Depot sells stainless steel hose clamps for really cheap. I have had 100% success with them over the years. They are very strong, won't rust and are a safe solution to re-using old hose clamps. Something to think about if you have had several hose clamp failures...