Is it necessary? Does the manual say when?

Thanks!

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2011 Prius

I haven't yet read an owner's manual the recommends changing (flushing) power steering fluid.... but then again most of the US auto manufacturers don't address the issue of changing brake fluid either! My MB owners manual doesn't recommend it. They probably don't recommend it because it's a messy job and the system isn't designed for a clean change.

A lot of do-it-yourselfers change power steering fluid anyhow. Any contaminant wear debris in the system not caught by the filter gets flushed out with the old fluid. Plus the old fluid may be degraded.

If you do flush the power steering fluid I recommend changing the ps filter at the same time, and don't use ATF. Over the years ATF has evolved with a different additive package that may be hard on seals designed for the old fluid. Use power steering fluid. Considering it's twice as expensive, and you typically use only two quarts for a flush, it's cheap insurance.

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95 E320 Cabriolet, 159K

Thanks, Kestas

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2011 Prius

MB sells their own PS fluid & there is a Febi PS fluid available from Phil. I use a suction gun and suck oil fluid out and add new fluid. Its takes about 3 quarts of fluid to get the system with clean fluid (car running).

HTH,

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Brian Toscano

Using a suction gun won't clean the system very well.

The proper and easy way to flush and change PS fluid is to remove the return line from the pump and lay it down in a drain pan. Remove the reservoir fluid and be prepared with about three quarts of Power Steering Fluid.

Have an assistant start the car and start turning the steering wheel back and forth lock to lock while you pour two quarts of fluid through the system. As soon as it starts blowing air after the second quart, signal assistant to kill engine.

Reconnect return line to pump and fill reservoir with fresh fluid. Have assistant start it up and watch fluid closely while the assistant turns the wheel lock to lock to bleed and take in fresh fluid. Add fluid until system is full.

This is the method covered on the ASE test. I have used this method on MB's and other cars with great success. It is quick and simple and cleans the system well.

Good luck,

Using a suction gun won't clean the system very well.

The proper and easy way to flush and change PS fluid is to remove the return line from the pump and lay it down in a drain pan. Remove the reservoir fluid and be prepared with about three quarts of Power Steering Fluid.

Have an assistant start the car and start turning the steering wheel back and forth lock to lock while you pour two quarts of fluid through the system. As soon as it starts blowing air after the second quart, signal assistant to kill engine.

Reconnect return line to pump and fill reservoir with fresh fluid. Have assistant start it up and watch fluid closely while the assistant turns the wheel lock to lock to bleed and take in fresh fluid. Add fluid until system is full.

This is the method covered on the ASE test.

Good luck,

I've had excellent results using the suction gun and three quarts of fluid. During the process I turn the steering wheel back and forth several times. I can see the fluid clear up as I go along, particularly between quarts 2-3. The fluid stays clear for 20-25Kmi and I change it at 25-30Kmi.

I don't recall what the MB factory procedure for this job is. I believe either way will do the job. And the suction gun only requires one person which may be all that is available for some people.

HTH,

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Brian Toscano

The problem with the suction gun is that you are managing to mostly change the fluid, but you are not getting the system flushed.

Additionally, doing it the ASE way is quicker.

Have a great day,

Please explain the difference between changing the fluid and flushing? Is there an ASE procedure for "flushing" a transmission that is different from using the MB procedure of draining the torque converter and trans pan? (I am asking seriously).

Thanks,

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Brian Toscano

I use the two-person method of flushing the power steering fluid as Larry described. I find the procedure more managable with the wheels off the ground. Less pressure is developed. With the wheels on the ground, the fluid comes out rather forcefully and I find it impossible to keep up with the flowrate.

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95 E320 Cabriolet, 159K

By pouring the fluid THROUGH the system as I described, you are using two quarts of fresh fluid, forced through the system to flush the junk out of the system and into the drain pan.

Merely sucking out fluid and replacing it will remove alot of the stuff that is ALREADY suspended in the fluid, but will not flush THROUGH the system dislodging junk that is around the valves, seals, and internal components.

Yes flushing with my method blows the fluid through VERY rapidly, and it takes only a matter of seconds to go through the two quarts, but this dislodges lots of stuff. After empty and the last of the fresh fluid is poured through, the system will be squeaky clean.

Hope this helps,

Is this the line that when the fluid is flowing goes from the sterring box to the pump or the other one?

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

The return line is the one with a slip fit hose into the reservoir, or a slip fit hose into a stub of pipe sticking out from the reservoir..

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum

I used the same method like Kesta's and believe that's the best method for flushing out power steering fluid. It's more controllable than starting the car and having someone to turn the steering wheel. You can also do it alone.

Eric

messy, but i used that method, it works. And Pyroil power steering fluid works fine, ExxonMobil now makes the dealer stuff.

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1984 380SL-driving and service privileges.