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Power Steering Filter Replacement and Flush
 
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Pelican Technical Article:

Power Steering Filter Replacement and Flush

Steve Vernon

Time:

1 hour1 hr

Tab:

$6 to $30

Talent:

*

Tools:

Turkey baster or fluid pump, 10mm wrench

Applicable Models:

Mercedes-Benz 300CE (1990-93)
Mercedes-Benz 300E (1990-93)
Mercedes-Benz 300TE (1989-92)
Mercedes-Benz E320 (1994-95)

Parts Required:

Power steering filter and fluid

Hot Tip:

Don't open the lines

Performance Gain:

Sharper steering input

Complementary Modification:

Check your steering linkage

There are several thoughts and methods on changing the power steering fluid in a W124. Some people claim that it is a lifetime filter and fluid, to which other people ask, "Then why do they make replacement filters and fluid?" I am not a big believer in lifetime fluids and if there is a changeable filter, I am going to change both the fluid and filter.

If you are going to change the fluid there are two schools of thought on doing it. The first school of thought is to completely flush out the system while simultaneously adding new fluid. This involves opening the return line to the reservoir and placing a large bucket for the fluid to empty into under it while being prepared to add several liters of clean fluid into the reservoir. Have someone start the car and turn the wheel while you are pouring new fluid into the reservoir so it doesn't run dry. I do not recommend this method for a lot of reasons. First: You will use a lot of fluid. You will be shocked at how much of a volume your pump can move, and the fluid is not cheap. Second: It can get extremely messy, as everything is slippery and moving under pressure. Third: If you let your pump run dry, even for a few seconds, you can severally damage it.

I prefer the "old school" method of sucking as much fluid as you can out of the reservoir, replacing the filter and adding new fluid. The fluid will not stay perfectly clean as there is still a fair amount of fluid in the lines and pump, but if you do repeat sucking out the fluid and replacing every couple of weeks eventually you will end up with very clean fluid at a much cheaper cost. Also, the fluid has been in there for years. It can wait a few more weeks until it is all changed out.

The radiator hoses have been removed for photographic purposes only, you do NOT need to remove the hoses to perform this work.

Locate the power steering reservoir just below the thermostat (red arrow).
Figure 1

Locate the power steering reservoir just below the thermostat (red arrow).

Undo the cap (red arrow, it just unscrews) from the reservoir (yellow arrow) and set aside.
Figure 2

Undo the cap (red arrow, it just unscrews) from the reservoir (yellow arrow) and set aside.

Use a turkey baster or fluid pump (yellow arrow) to remove the fluid in the reservoir.
Figure 3

Use a turkey baster or fluid pump (yellow arrow) to remove the fluid in the reservoir.

Push down on the plastic stalk (red arrow), remove the 10mm nut (green arrow) and remove the plastic stalk and spring.
Figure 4

Push down on the plastic stalk (red arrow), remove the 10mm nut (green arrow) and remove the plastic stalk and spring.

Remove the old filter (red arrow).
Figure 5

Remove the old filter (red arrow).

Remove as much fluid as possible and clean the inside of the reservoir (red arrow).
Figure 6

Remove as much fluid as possible and clean the inside of the reservoir (red arrow). Install the new filter, reset the spring, stalk and the 10mm nut. Fill with new fluid. If you want a fuller flush, start the car and turn the wheel a few times, then drain and refill the reservoir with clean fluid. Repeat until the fluid remains clear to its original color.


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Comments and Suggestions:
quest1966 Comments: I found it quite simple and clean to do the following:
1 Jack up the car so both front tires are off the ground. I did this while bleeding the brake lines so the wheels were already off.

2 Detach the return hose, stick it into a 3/4" ID clear hose running to a drain bottle or pan underneath the car. For assurance, place another short hose 7/16" ID over the reservoir intake tube and point it or kink it up to avoid any leakage onto the engine or ground. No pressure will be on this hose.

3 To the inanition key to the 'on' position but do not start, just need to unlock the steering wheel. Turn the steering wheel from lock to lock once to lower the fluid level in the reservoir. Be sure to leave some fluid at the bottom to avoid any air bubbles into the pump.

4 Pull out the filter. I grabbed it with needle nose pliers and wiggled it out.

5 Either suck the remainder out with your tool of choice or turn the wheel more, lock to lock, until the fluid level reaches the bottom but not empty. This will reduce the amount of old fluid mixing with the new fluid which reduces the total fluid needed to fully flush the system.

6 FIll up the reservoir. Turn the wheel more, lock to lock. If you have an assistant, they can turn the wheel back and forth while you continue to fill the reservoir and watch the old fluid coming out the return hose into the clear drain hose.

7 After about 1 quart has been poured into the reservoir, the new clear fluid will start coming out. The old fluid will be noticeably darker. Stop there, install the new filter and plastic stalk/level gauge. If the fluid level is too high, turn the wheel a bit more to bring the fluid to the proper level.

8 Remove the drain hoses and re-attach the return hose to the reservoir. Be sure to tightened the hose clamp securely.

9 Replace the cover with a new gasket. Lower the car and you are off and running.

10 Check the fluid level after your next trip wherever and top off as needed.
April 12, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 

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