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Old 09-03-2021, 01:49 AM   #1
855T
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Default At my wits' end with air in the power steering system

2010 WRX with 70k miles or so.


After months of trying to figure out why the eff I was having a ton of vibration in the wheel at speed, I replaced my wheels with some really nice OZs and took care of 90% of the issue. Now that the wheel wasn't shaking out of my hand on the freeway, I began to notice pretty awful steering kickback and shudder, particularly early in drives, and particularly in hard cornering, often with PS pump noises. I guessed an issue with the power steering, so I replaced the belt (and the AC belt while I was in there) with no benefit.



Next, I figured air. So I replaced the fluid and o-ring where the suction hose meets the pump. No change, maybe a little worse. Replaced the clamps - no change.



Next, I bought an OE suction hose, a new o-ring, fancy t-clamps, and replaced the suction hose from the reservoir to the pump along with the o-ring (again) and essentially all new fluid (again). I moved the wheel lock to lock 50 or so times, waited, did it again 30 minutes later, waited another 30 minutes, and then started the car.



The pump is audibly whining at idle, which isn't something it's ever done before. Tons of foaming in the reservoir when steering. Turning the car on, the fluid in the reservoir drops. Turning the car off, it rises high enough to seep/spray out of the reservoir at the lid.



So, I let it sit for a long time, then did the car-off wheel sawing procedure again, started it up again after waiting, same issue. There is so much air in the system that it is instantly foaming the reservoir when the car is on even without touching the wheel.



I have no idea what to do next. Buy a handheld vacuum pump and try to pull air out that way? Anything else to try?
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Old 09-03-2021, 02:04 AM   #2
supermarkus
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I chased my tail for months with a noisy, leaky o ring. When I did manage to get a seal it was still juddering and whining. Ended up getting a new oem pump to finally fix it. That was three years ago and the replacement is starting to get loud too. These power steering pumps just suck.
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Old 09-03-2021, 07:12 AM   #3
snow_bound26
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Default At my wits' end with air in the power steering system

You may also have a leak in the rack as well
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Old 09-03-2021, 11:34 AM   #4
855T
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I'm going to try pulling a vacuum at the reservoir later today.

I'd assume that a leak anywhere would result in fluid loss given that the rest of the system is under pressure, but what do I know.
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Old 09-03-2021, 12:02 PM   #5
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Quote:
Originally Posted by 855T View Post
I'm going to try pulling a vacuum at the reservoir later today.

I'd assume that a leak anywhere would result in fluid loss given that the rest of the system is under pressure, but what do I know.
I have done that. You'll want to jack up the front end and turn the wheel lock to lock several times while applying vacuum. if you're STILL pulling air out of it after that then you've got a leak.

IF you find that you need to replace the pump unit do NOT use a remanufactured unit. I have been burned by reman pumps (and starters) many times and refuse to use them.
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Old 09-03-2021, 12:10 PM   #6
klinebau
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If you continue to get air in the system, I would tend to think that is related to the suction side (reservoir to pump). I recently diagnosed a similar issue with my '06. To solve it I put new hose clamps on hose from reservoir to pump. I also replaced the o-ring which connects that line to the pump.

One bad thing I did was order a non-subaru o-ring from amazon which was advertised as the correct part. That o-ring must have been slightly too small because it would let air in on cold mornings. I then purchased the correct subaru o-ring and that solved the problem. If you don't have the correct subaru o-ring, this could be your problem.
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Old 09-03-2021, 12:15 PM   #7
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Quote:
Originally Posted by 855T View Post
I'm going to try pulling a vacuum at the reservoir later today.

I'd assume that a leak anywhere would result in fluid loss given that the rest of the system is under pressure, but what do I know.


There's a high pressure side and a low pressure side. When a leak is just starting it will sometimes pull air without leaking fluid on the low pressure side. Let it go long enough and then it will start to leak fluid.

I will admit this system isn't the easiest to purge air from. Even turning the wheel too fast can result in poor bleeding. I typically don't recommend going to full lock when turning the wheel and make it take several seconds per full rotation.
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Old 09-03-2021, 12:50 PM   #8
benflynn
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Electric power steering pump time
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Old 09-03-2021, 04:40 PM   #9
855T
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Update: the vacuum pump confirmed ongoing leakage at the o-ring. I'm going to replace it (for the third time) and RTV the **** out of that area. This is poorly engineered.
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Old 09-03-2021, 06:04 PM   #10
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Another update:

I got the o-ring to seal. It's not yet clear whether this will solve the problem but the foaming/insanity is already vastly reduced. I'll update either way.

Not well-described anywhere else is the specific procedure to get that thing to seat properly, so for future idiots like me looking for this information:

1. Use a narrow turkey baster (a battery filler or similar) or a pump to remove as much fluid from the power steering reservoir as possible.
2. Loosen the 10 mm bolt holding the suction line and elbow to the top of the pump.
3. Pull the elbow out of the top of the pump and raise it in the air to keep fluid from flowing out, and mop up any spillage.
4. The old o-ring will be either on the elbow or inside the receptacle on the top of the pump. You might need to use a rag or the baster to remove some fluid from the cavity to find it and reduce spillage.
5. Place the new o-ring into the cavity, NOT onto the elbow, and ensure it is flush with the bottom of the cavity.
6. Remove the hose clamp between the suction hose and the elbow, making sure to keep the hose elevated to minimize spillage.
7. Clean off the elbow and then place it into the receptacle. You will feel resistance as it slides through the o-ring and seats.
8. Reinstall the bolt holding down the elbow.
9. Reattach the hose to the elbow and tighten the clamp.

At this point, bleed the system however you prefer.

As far as the vacuum pump, can't recommend it enough. I used the Mityvac MV800 manual pump along with the MVA660 power steering adapter. The adapter is not appropriately sized for our reservoirs but can be held in place to check vacuum. The second I applied vacuum, I could hear the elbow connecting the suction line to the pump wheezing.

Last edited by 855T; 09-06-2021 at 08:38 PM. Reason: updated for clarity
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Old 09-04-2021, 08:06 PM   #11
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Unfortunately I found that the elbow/pump union is so poorly designed that even a new elbow and o-ring didn't help me. Good luck. I tried to subaru bond that elbow too and didn't have any luck with a long term fix. Still foamed like mad. Really shouldn't rely on a fastener an inch away from what you're clamping to provide adequate clamping force through plastic in a hot engine bay.
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Old 09-09-2021, 06:43 PM   #12
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Update: I do believe I got all the air out of the system, however I am still able to hear pump whine from time to time at full lock, and the original reason I went down this path - occasional steering wheel shudder and kickback - remains.

Short of replacing the pump and rack, I'm giving up...the new Z looks nice.
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Old 09-10-2021, 11:31 AM   #13
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Be sure to lubricate the new O-rings with PS fluid prior to install!
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Old 09-15-2021, 01:01 PM   #14
855T
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...and we're right back to air in the system and violent kickback over bumps. I'm going to try reseating the o ring one last time, this time with a ton of RTV on and in the elbow.



Related, I spilled a bunch of ATF down the front of the pump when changing the suction hose and now I get some good smoke when the engine gets hot. Well-engineered across the board.
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Old 09-15-2021, 02:43 PM   #15
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I still think it's a leak on the low pressure side. Probably one of the lines coming off the rack. Could also be a worn seal in the rack. Sometimes these things allow air in but no fluid out for a while. Then you'll start seeing them get wet in certain areas.
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Old 09-15-2021, 04:25 PM   #16
855T
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Even if the system holds vacuum? I can get it to 20 mmHg when it's hot or cold and the needle does not move.
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Old 09-16-2021, 01:19 PM   #17
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855T5<744t+t
Megasquirt1 fo life
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Old 09-17-2021, 12:04 PM   #18
855T
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Quote:
Originally Posted by benflynn View Post
855T5<744t+t
Megasquirt1 fo life
I had a 944T first, but at the end of the day, basically everything about the 8 series was superior except which wheels were driven.
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Old 09-17-2021, 01:30 PM   #19
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Replace the rack and go back to enjoying your car.
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