Does anyone know what it is for? Is it for the steering wheel pump?

It is below the minimum currently and would like to know what to use to top it up / change it. The service book does not refer to it at all, so I presume one never changes it. But on older cars I have noticed it becomes thin, watery like, so I am sure it does need to be changed.

"Hydraulic fluid" is typically the name used for brake fluid > as the brakes use a hydraulic piston/cylinder design.

MB use DOT-4 fluid. [at least my 97 C230 uses DOT-4]

Brake fluid should be changed every two years > as it is "hydroscopic" >> it absorbs water vapor > which in turn lowers the boiling point of the fluid > which lowers the thermal efficiency of the fluid.

There is a specific "power steering fluid" for the power steering system of the car

Is this a station wagon or sedan - they are different.

The wagon has a reservoir in the front, left corner of the engine compartment. That reservoir feeds an engine driven hydraulic pump. The pump supplies both the power steering and the self-leveling rear suspension.

The sedan has a more conventional setup, with an engine driven power steering pump with integral reservoir.

I'm not up to speed on the fluid requirements for either...

- JimY

Yes it is the "wagon" (we call them estates here).

The service booklet does not mention it, but I know on my old Peugeot the steering pump fluid was getting hot (that is normal) and very very watery, so I changed it. So do I need to change it at all? The car is 4 years old and has covered 25K miles.

On my 95 e320 wagon (124) it has the pump which operates the rear self-leveling system and the power steering. However, the power steering fluid resevoir is located directly atop the pump, while the rear leveling suspension resevoir is located in the left front corner of the underhood area, and uses a special fluid which I purchased from MB. My car was low on this fluid for some time however, with seemingly no side effects.

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2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro

Ah, I neglected to notice you were across the pond, otherwise I would have directed you to examine beneath the passenger side of the bonnet...

The 124 and 210 chassis estate cars are rather different in this area. The 124 uses a "dual pump" which provides hydraulic pressure for both power steering and self leveling, but uses separate fluids to do so. It contains a typical small reservoir for the power steering fluid and in addition is plumbed to the larger reservoir for the leveling system. A common problem is a failing seal and the pump mixing the two fluids together.

The 210 is simpler, with only the larger reservoir and the same hydraulic fluid powering both steering and suspension.

MB does not specify any change interval for this fluid (neither did they for the 124 suspension). The conventional wisdom on the earlier cars was to change the fluid every 3-4 years. My personal opinion is don't bother, that is overkill. With only 25K miles in four years, just top off the fluid and don't worry about it. Your owners manual should specify the fluid required. Likely it is only available at the main dealer, or from a Mercedes specialist.

- JimY

I also own a 2001 E320T. My approved fluid booklet dated October 2000 (which may have changed by now) lists three different approved hydraulic oils for various MB's:

For the 600 sedan, MB part no. 100 890 00 11
For the load leveling system, hydropneumatic suspension, hydraulic soft top, 4matic, ASD, MB part no. 000 989 91 03 10
For tandem pumps with common oil reservoir for steering and level control in E-class, Model Year 1996 (aka W210 vehicles), MB part no. 001 989 20 03 01

I assume that each oil has different additives to handle the specific application, with the 210 oil having to work with the self leveling system and power steering. My guess is that non-purists just buy the generic Febi oil (for the 124's) and use it in the 210's. Similar to when I worked on 600s with bad hydraulic systems and would find that PO or previous mechanic would have substituted ATF in place of the approved (and very expensive even in the 80's) MB oil. Costly mistake. Common wisdom on 124's which should be applicable to 210's would be to change the fluid and filter at the resevoir every 2 to 4 years. In my experience, there is a big difference in the color of clean fluid and used fluid. I have not changed mine yet but I expect to soon. I will let you know how it goes. Mark

On my 124 wagon I changed the suspension fluid @ the 30K mile major service intervals. Very little difference in color between the ~three year old fluid and the new. The old fluid was still almost completely clear. So my opinion is that it was overkill. But then again, it was only $30 once every three years - hardly breaks the bank.

- JimY

The fluid I added came a Mercedes specialist. It came in a blue plastic container and had the Bilstein name on it. The new fluid was clear, what is in the tank is nearly black.

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2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro

Troverman, that was my experience with my '91 TE. Probably had never been changed before I changed it at 113K mi. Interesting that the 123 wagons had paper filters, the 124 wagons have fine plastic screen filters, and the 210 wagons have reverted to paper filters. I would venture a guess that the paper filters filter finer particles than the plastic screen filters. The oil in my 210 wagon has not been changed in 80K mi. and is starting to darken. Definitely time for a change. Mark

I own a 2000 E320 wagon. I know that my MB keeps hydraulic fluid #001. Now it has pretty dark color and I consider to change it soon.
Guys, do you know anything about Synthetic hydraulic oil: Pentosin CHF 11S? Does anyone tried to use it in self-leveling system?

Sorry, not sure about the Pentosin--I used Bilstein fluid which is OEM, bought from an MB indie.

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2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro

Changing it is definitely a good idea if it hasn't been done yet. However, keep in mind that the new fluid color will turn dark very quickly as well. It just does that! I used Febi-Bilstein hydraulic fluid as well, which is OEM and can be purchased online instead of the dealer for much cheaper. Good place is ***************. It think it's like $8 vs. $20 plus at the dealer. It takes less than a liter to replace the reservoir. Here is a link: http://www.***************/search/product.aspx?sid=1xjvai55s5ag1tiuhsipm555&makeid=800016@Mercedes&modelid=1387605@E320%204MATIC&year=2002&cid=98@Fluids%20%26%20Chemicals&gid=7607@Hydraulic/Suspension%20Fluid

Bansai, that fluid requirement for our 2002 wagon is somewhat "unique". It's made by FUCHS and is available ONLY thru the dealership from what I can tell. Think: per litre

Also, Pentosin is not an suitable alternative for our car. Refer to the label on the top of the reservoir...part number is right there.

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1998 W210 diesel (wiped out by a texter)
Baum spring compressor "for rent"

Thanks uberwgn!
I already know that.. I bought one liter such of fluid gold from MB dealership (they charged me $35 for one bottle )...
But I'm guessing that it would be not enough.
My 2000 wagon uses synthetic based fluid 001.989.20.03.10 as your.
I've seen Febi/Bilstein fluid at local store. This fluid has mineral base and probably is not compatible with mine.

Why I thought about Pentosin CSF 11S. I heard that new W211 wagons use it at their suspension self-leveling system. Might be it will compatible with our system as well?