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When should I Change Or Flush The Power Steering Fluid In My Subaru?

When should I change or flush my Power Steering in my Subaru?

One fluid that often goes neglected in a Subaru is the Power steering fluid, other than calling out the occasional inspection Subaru doesn’t really specify any real service interval and as such we have over the last few years dealt with more and more power steering fluid related symptoms.

The design of the 2000 and newer models creates a situation where old fluid can create power steering symptoms as well as take a toll on seals and internal components as well.  The fluid in the Power steering system is a hydraulic type fluid and in many applications automatic transmission fluid such as Dextron III is used.   There is not a drain plug for the fluid, the systems typically don’t have any type of filtering device and the fluid actually can become dirty pretty quickly.  The best way to deal with this is to flush out the fluid; at our shop we use a power steering flush machine with a flushing agent and some fluid conditioner when needed and offer to change out the fluid in the reservoir during a 30/60/90k service included if that’s al that is needed.  At home you can use a turkey baster to remove the fluid in the reservoir but you will have to do this, then re fill several times before you have even remotely clean fluid.

The newer model Subaru vehicles can suffer from old fluid over time taking a toll on the return line o-ring which can create a small air leak causing the fluid to become aerated, this will typically start out as a cold engine only symptom gradually becoming worse  and if not dealt with can eventually damage the power steering pump.

We have simply replaced the fluid on many H6 models from 2001 to 2004 to eliminate a cold engine growl or whine type noise being emitted from the power steering pump.   The 2000 to 2009 4 cylinder models can have an o-ring that will no longer seal when cold as a result of the fluid causing it to shrink over time and no longer seal until the o-ring warms up and expands into the sealing body of the power steering pump.

It has been a common repair for many years to reseal the power steering pump do to external fluid leaks (typically after many miles). On the 2000 and newer models we have observed less external leaks but more actual symptoms however,  which at a minimum require  you to replace the return line o-ring and perform a flush if there is a power steering type noise as a result of fluid aeration.

I would like to point out that a loose or worn power steering belt can cause noise and symptoms as well, please don’t automatically assume that after reading this article that you need to reseal your power steering pump

If you are a local customer and would like to schedule a power steering system flush you can do so below.

If you are somewhere else in the country or the globe for that matter and have a power steering type noise there isn’t much we can do for you over the phone that we haven’t already tried to address on the website under two separate articles this one and the other is here Power steering problems Explained.

I Hope this helps!

Justin

All Wheel Drive Auto

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About the Author

All Wheel Drive Auto is a unique independent Subaru service & repair facility. We combine years of dealer experience with a local neighborhood shop atmosphere. We use Subaru parts & test Equipment and have the expert knowledge to fix it right the first time.

Comments (18)

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  1. Robert Thomas says:

    I have a 2004 Subaru Forester with 105,000 miles. From a cold start, steering right or left is very hard and bumps. After the initial couple of turns it is then okay until car has sat and gotten cold again. There is no noise associated with the problem. My mechanic, who has not felt the problem, changed the power steering fluid and checked the system but reports they couldn’t find any problem in the system. However, the problem continues and appears to be lasting longer after a cold start. Any suggestions? I am in Jacksonville, FL, so coming in is not an option. Any direction you can provide will be very much appreciated.

    • Justin Stobb says:

      Hi Robert,

      Sounds like a weak pump, but the seals internal in the rack could be swollen as well.

      The most common is the pump, there is no port to check pressure and gauge against specs I am afraid so this is a Experience type of a call for a Technician some may be uncomfortable doing this. I know that even here if we run into something we cant “prove” we will only make a suggestion to a customer and hope for the best, its not an exact science, as the market place wont bear the costs.

      Justin

      • Robert Thomas says:

        Hi Justin,
        Thank you for your reply. Something new has just occurred which may or may not affect your response. This morning, with temps at 31 degrees, as I experienced the ‘bumps’ while turning the stearing wheel, the ‘brake’ and ‘battery’ lights on the dash flashed on and off at each ‘bump’ of the wheel. Any possible correlation? Thanks again for your help.

        • Robert Thomas says:

          Problem turned out to be a bad belt (slipping). Replaced the engine belt and the problem went away.

        • Justin Stobb says:

          The brake and battery light make my think something with a main battery connection such as the positive or negative battery cables being losse at either the battery or engine.

          Id start with inspecting those items

          Hope that helps

          Justin

  2. faye chester says:

    Hi Justin,

    I have frequently visited your website for repair clues with my 2001 subaru legacy wagon. Often I have found valuable suggestions. This time I have a power steering question. fluid is leaking out as soon as it is put in and I have lost steering power. I had the rack replaced about 8 months ago, the fluid appears to be leaking from one of the two lines leading to the rack. Any ideas or comments are appreciated. Unfortunately, I’m in Virginia and not near your facility.

  3. Vince says:

    Thank you for the detailed yet simple explanation. It was spot on with the troubles I was experiencing.

  4. Jon Thomas says:

    Justin,

    My son was just deployed and left me with his 2009 Subaru Forester to periodically drive while he is gone. The Forester has a severe power steering related noise and he had a mechanic check it. They said the problem was a kinked line, or some type of obstruction in the lines and that the pump should be replaced. I took it to a mechanic here and they say the rack is the problem, that the fluid is very dirty, but that it is circulating. I plan on taking it to another mechanic to try to get another opinion. They can’t find a local supplier for the rack if that does need to be replaced.
    I have two questions, first, your thoughts on what’s wrong. Secondly, is there somewhere on line I can get quality Subaru parts at reasonable price . Any suppliers I should stay away from.

    • Justin Stobb says:

      Hello Jon,

      I would start with allowing someone that Knows Subaru have a look and get the right answer the first time.

      I would stay away from anything that wasn’t an original type part for a 2009 Forester.

      -Justin

  5. Toby Gardner says:

    Justin
    Is there any way you could provide the Subaru part number for the return line o-ring for a 2002 Subaru Legacy 2.5L SOHC wagon? I had the power steering fluid changed but my mechanic here was not able to find the proper o-ring.

    Thanks for all the great information on this site.

    • Justin Stobb says:

      Hello Toby,

      So there are two different part numbers for the o-ring

      34439 AE00A
      34439 AE020

      We usually take it out and match it.

      You could always call the Dealer with your VIN number and ask them to verify when you go into pick one up.

      -Justin

      • Toby says:

        Justin
        Thank you very much for this info. If I get the o-ring and go back to the mechanic they need to flush and replace the power steering fluid AGAIN, since they will be opening up the line, correct? Just want to make sure I get this done right. Again, wish you guys had chains through the country!

        • Justin Stobb says:

          They need to do what ever they have to to remove the air out of the system. We call it pump priming, or bleeding the air out. Just what ever they do get the air out after replacing the o-ring and you should be all set.

          -Justin

  6. James says:

    I have a 2004 WRX with 114k miles since new and its power steering fluid has never been changed. No leaks yet though. Is Valvoline MaxLife DEX/MERC ATF a suitable fluid? I wonder if it will help/delay the older seals when they eventually leak. Or should I stay with the ATF they sell in the dealership?

    Really appreciate your site!

  7. Heidi s. says:

    According to my mechanic I needed a “full fluid flush” on my 2006 Subaru forester. This, he said, will eliminate the “chattering” and initial “creeks” in turning at start up. He also replaced the front brakes due to a high pitched “warning noise” I was hearing while driving. He indicated that with all fluid flushed I should be able to know that was the ” fix” to my problem AFTER about 500-1000 miles of driving, as ” it takes a while to get all the new fresh fluids throughout the machine” . That seems weird to me, is that correct?
    Please advise :)

    Heidi

    • Justin Stobb says:

      Hello Heidi,

      If the power steering system is having an issue and the diagnoses is contaminated fluid, yes it needs to be flushed, no it shouldn’t take 1000 miles to know if its going to be fixed.

      If its the transmission that’s being flushed and also and additive put in to correct “torque binding” on turns, yes a flush will help with an additive and yes it could take a bit to know if its going to work.

      Because you did not specify what was being flushed I gave you the two possibilities I could think of.

      -Justin

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