Hydraulic fluid/Power Steering fluid

Hydraulic fluid/Power Steering fluid

Submitted by EZduzit on 05-04-2012

Power Steering fluid/ Hydraulic fluid level

My 1991 MB 560SEL makes noise when I turn right or left when driving. I think it needs Power Steering fluid. However, the Owners Manual only mentions Power Steering fluid but doesn't say where the fluid goes and how much to fill. It only states that it needs 1.4 quarts. Neither does it say how much Hydraulic fluid should the Hydraulic container have in it and to what level. There is a wire around the container (which has a small knob on top) and it appears that it is full to that wire but the container seems only half full. Is the Hydraulic fluid and Power Steering fluid one and the same? I'll have to see if I can buy some online but where? I don't live anywhere near a MB Dealership and I look forward for some information. Thanks!

Posted on 05-08-2012
Fluid Changes

Thank you George for all this extremely useful information. I printed it and since I am not mechanically inclined I will bring it with me to the mechanic shop wherever I go. I think I will risk driving to one of the MB shops I mention in the reply to Jonathan. I checked the Power Steering fluid and it's nearly black. I purchased this vehicle several years ago and I'm not sure when the last service check-up was done. It needs it badly. As soon as I have enough cash on hand I'll take it in. Probably the best place is where the car was originally sold: South Burlington VT.

But I want to thank you again for all of this valuable information George.

Best Regards,

George Murphy
Posted on 05-07-2012
Fluid changes

Automatic Transmission: MB Automatic Transmission fluid. Fluid change 8.1 US qt.<

Dexron III is an alternate for that transmission - available at auto part stores

Power Steering: MB Power Steering fluid. 1.4 US qt.<
Same as transmission

Level Control: Hydraulic fluid. 2.1 US qt.<
I have Febi brand available - contact me at 

Accelerator Control linkage: Hydraulic fluid.<
I use lithium grease

Auto transmission fluid change

Changing the fluid and filter in an automatic transmission is only slightly more difficult than changing engine oil.  It should be done at least every 30,000 miles; more often under dusty conditions.  If you must add fluid between changes, make sure your wiping rags, funnel, and other tools that contact the dipstick are scrupulously clean.  Your automatic transmission cannot tolerate dirt like your engine -- it has many more moving parts and small passages that can be damaged or plugged by dirt.  Be sure to purchase the correct transmission filter - it is best to buy the "kit" as it includes the filter, gasket, and new copper sealing rings for the drain plugs.
Points to remember when changing transmission fluid include:
    1) Some M-B automatic transmissions don't have a drain plug like the engine.  You must remove a bolt connecting one of the cooling lines or possibly the dipstick tube fitting - this will allow most of the old fluid to run out. (On 126 cars, you will have to remove the cross member under the TC housing to remove the pan). Then remove the bolts that secure the shallow pan that covers the bottom of the transmission.  Loosen the bolts in a sequence that allows one corner of the pan to drop down first so the fluid will run out in a small stream. Then carefully dump out the rest of the fluid as you lower the pan.  The filter will then be visible - it looks like the new one you bought before you started this job. The filter is held in place with two or three bolts or screws.
    2) Install the new filter and make sure it is properly seated in place.  Clean the pan, install a new gasket and replace the pan and drain plug (use new sealing ring).
    3) Be sure to drain the torque converter - it holds about three quarts of fluid.  Locate the converter drain plug by manually turning the engine over.  Use a large screwdriver to engage the torque converter and rotate it until the plug is aligned with the access hole. Make sure you turn engine in running direction.
         CAUTION: Use care with the screwdriver, don't take a big "bite" to avoid breaking the aluminum torque converter cover ribs.
         The plug is usually a 5mm hex socket head screw, so you will need a metric hex driver to remove it.  Remove the plug and allow the oil to drain out.  You should also disconnect the transmission cooling lines and allow the old fluid to drain out.
    4) When all fluid has been drained, replace and carefully re-tighten all connections and drain plugs.
    5) Measure the total amount of old fluid that was drained. Make sure the car is level. Refill the transmission first with four quarts of new transmission fluid, then start the car to pump the fluid into the torque converter and cooler. After about three minutes, stop the engine and add the rest of the needed fluid – about 2.5 quarts (If you add all the fluid at once, it will overfill the transmission and run out the rear seal or vent).  Keep in mind that it will take more fluid than listed in the owner’s manual to fill it since you drained the torque converter and the cooler (normal M-B service does not include draining the torque converter or cooler).  If you overfill the transmission, be sure to remove the excess fluid as too much fluid could damage the transmission.
         Dick Gale of Santa Fe, NM(an owner of several SLs) showed me a neat trick for adding small amounts of oil to your automatic transmission through the tiny dipstick tube.  Wipe off the dipstick tube around the top and withdraw the dipstick about 12 inches.  Rest the dipstick against the top of the fluid container so that the fluid will run out on to the dipstick and down into the dipstick tube.  The transmission fluid is thick enough to run down the dipstick without dripping.  Pour the fluid slowly about a half pint at a time.  Check the level with the engine running and the transmission in Park position.
    6) Check the fluid level in accordance with the instructions in your owner’s manual.

Power steering fluid change

The power steering on your Mercedes Benz is a simple hydraulic system which
normally uses automatic transmission fluid.  Check your owners manual for the
correct type.  The system reservoir usually has a filter inside which must be
changed when the fluid is changed--so it is best to do it at this time.  When
buying the power steering reservoir filter, be sure to have the chassis number
of your car and the power steering pump manufacturer's name and model number
(they're on the pump) available for reference.

Procedure -

     1)    You'll need a four-quart capacity container handy to catch the
           old fluid, plus three quarts of new fluid.  Remove the cap, spring, and
           retainer from the reservoir and reach down inside to remove the filter.
           It's about the size of a hockey puck or it may be a ring-type filter.
           Then using a turkey baster or  a Topsider Oil Changer, suck out all the
           old fluid from the reservoir.

           CAREFUL - if the car is warm the fluid may be hot!

     2)    Loosen the hose clamp on the return line to the reservoir and remove the
           hose. Note: The high pressure line generally has a threaded connector at
           the reservoir--don't disconnect it.  The return line is usually clamped to
           the reservoir return pipe. (You may have to plug the return pipe to
           prevent fluid from running out)  Place the empty container under the end
           of the return hose to catch the old fluid as it runs out.

     3)    Have a helper start the car.  As the old fluid is pumped into the
           container, quickly add new fluid to the reservoir--always keeping the
           level in the reservoir at least half full to avoid getting air into the
           system.  Have your helper quickly turn the steering wheel full right and
           full left several times to thoroughly flush the steering box.

     4)    When fresh new fluid appears out the return hose, the system is flushed.
           Stop the engine. Reconnect the return hose to the reservoir and install
           the new filter.  Top up the reservoir to the full mark and reinstall the

Hydraulic fluid change


Application: 123 & 124 wagons, S-class sedans, 6.9s, 201 16-valve


Here's how its done: (Have 2 friends ready - one heavy friend at the rear
of the car and one in the driver's seat standing by to help...(can be any

1 - Remove the fluid return line from the top of hydraulic fluid reservoir
and remove fill cap - use a piece of scrap hose to route return line oil to
a 1 gallon container placed under the car to catch old fluid as it comes out.

2 - The filter is located under the fill cap - part no 002-184-55-01 -
remove old one and leave cap off reservoir.
(Some Euro models require removal of the level control valve from the top of

3 - Have 3 liters of new fluid ready to pour into reservoir - take lid off
bottle (part no 000 989 91 03 - $11 per liter from me) and remove foil
seal because you have to be fast about this.  Use a turkey baster to remove
all old fluid from the reservoir, then add about a liter of new fluid.

4 - Have one friend start the car; have other (heavier) friend bounce rear
of car to exercise rear suspension while you pour new hydraulic fluid into
reservoir as it is pumped through system and into catch bucket under car -
this is called feed and have to keep feeding in new fluid as the
old fluid is pumped into catch bucket under the car.

5 - When new clean fluid emerges from return hose, shut off engine (and stop
bouncing rear of car). Fill reservoir to correct level as marked on side of
reservoir. Install new filter and re-connect return line to closure cap
assembly. Start car and check for leaks and top up fluid level if necessary...

Here is an amendment for exchange of the filter in Euro/full-hydropneumatic
 suspension systems:

1. Put hydropneumatic valve into position M (assembly) all the
   way to the stop by removing retaining ring on level selector
   linkage with retaining ring pliers.

2. Wait about 2 minutes for depressurizing of the system (oil stops

3. Remove two hydraulic lines which lead straight down with 12 mm
   open box wrench.

4. Unscrew valve with two 8 mm nuts from container and remove
   by slightly bending upwards.

5. Unscrew filter holding nut with 10 mm wrench while counter
   holding screw with 3 mm Allen wrench.          

6. Clean seals etc, exchange filter and reassemble. Replace spring
   if broken or too loose, since it acts as oil bypass if filter


Posted on 05-05-2012
I would Not take your car to

I would Not take your car to a dealer...they simply know Nothing of a 126 these days..  Instead, you would be Far better served finding an Indy who is Familiar with your chassis.

As for power steering, MB makes their own, it's clear in can buy it in the febi bottle for a good bit less then the Genuine MB, same exact bottle I might add.  I'm also a big fan of Pentosin CHF 11S, it's an Excellent PS'ing fluid that I've had very good luck with.  If the age of the fluid is unknown, a few quarts and a new power steering filter would make for a good flush kit.  You don't want to fill the reservoir to the very top as the fluid does expand as it warms, fill it too high and it will leak out of the top/make a mess.
A bit of an aside, but I find that once the power steering system starts to leak, ATF seems to be tougher on the suspension bushings that it leaks on to then power steering fluid, suspect differences in the additive package have something to do with it.

The hydraulic fluid is also readily available, there is a screen in the system that should be cleaned/checked for tears on a regular basis..and again, if it's age is unknown a flush is a Wise thing to have done.

For what it's worth, older Mercedes really detest sitting, you would do your 560 quite the favour by getting her out on a more regular basis.  

@ the very least, be sure to change your oil yearly.  Brake fluid every 2 and coolant every 3.  


Posted on 05-05-2012
Not take my car....

Thank you Jonathan for your sound advice. There is no one around here familiar with my Benz although they claim to have experience working on foreign models. I'm far from being mechanically inclined. Adding windshield solution is the extent of it. My 3 choices are to take it to Mercedez-Benz dealers. The first being where it was originally sold: Burlington VT. Another being Syracuse NY; both 150 miles from here. The other choice is Cornwall Ontario but the tax is 15% non-refundable for U.S. citizens. At least they work on Mercedes at the very least they know something rather than nothing about these fine automobiles.

What is a febi bottle? Can I find Pentosin CHF 11S at an auto parts store such as NAPA or Advance Auto Parts? Perhaps they can order same for me? I'll have to check on that and MB products such as Hydraulic fluid from online stores as well. I'm waiting to hear from George who wrote to me earlier to see what he has to say.



Posted on 05-05-2012

Hi George,

Thank for you quick response. Here's what the Owner's Manual states: It appears to be very specific as to what can be used.

Automatic Transmission: MB Automatic Transmission fluid. Fluid change 8.1 US qt.
Power Steering: MB Power Steering fluid. 1.4 US qt.
Level Control: Hydraulic fluid. 2.1 US qt.
Accelerator Control linkage: Hydraulic fluid.

I drive this car less than 1K miles a year and put it in storage in the Fall. Is it safe to just add some fluids for this year since I plan to take it to an authorized MB dealer next year to have everything checked? Or should I have a local mechanic shop do a complete change of fluids? I have no idea where to add the Power Steering fluid as I can see no container for it. I surely would need instructions even if I take it to a local garage (I don't have much trust in them as they have done me wrong in the past).

Let me know George exactly what I need and how much it will cost me + shipping. Thank you for your kind offer.


George Murphy
Posted on 05-04-2012

They are two different types of fluid.

Power steering fluid for your model is ATF (Automatic Transmission Fluid Dexron III or IIIe ) available at any auto parts store.

Hydraulic fluid is MB special or I can send you what you need.

Let me know if you need instructions for changing each fluid . . .