i've done a search but nothing specific to the w126.

for the 90 350sdl, what is the proper level for the Power steering fluid. It does not seem to have a "max/min".

is dextron III aft ok to use?
where is the p/s filter?
if i were to drain and replace the fluid, is the drain on the steering box itself?

do you have any advice if the fluid is clearly leaking from the steering box?

any last minute pitfalls before i take the plunge and r/r the fluid or is it just like changing the oil (drain and fill)?

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Ben
1987 190d 2.5Turbo

if you insist on using ATF, use type F.

there are min/max marks inside the reservoir... or just fill it up to 'mostly full' (1" below the rim of the cap)

filter is at the bottom of the reservoir.

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what is the proper p/s fluid? does it have to be MB p/s fluid or can i just use regularly branded P/S fluid from autozone?

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Ben
1987 190d 2.5Turbo

generic p/s is fine

there is a drain on the str box... but you might not get all the fluid out and it will take a long time. Good idea to drain at least some from that bolt though.

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The way I did mine was get a turkey baster to suck out as much fluid as possible from the resivoir while the p/s drain plug on the gear box was out. Then you will see the filter at the bottom of the resivoir. I then turned the steering wheel as much as possible left to right (WITH THE CAR OFF!) to get the excess fluid into the res. Then suck out the rest with the baster. Put plug back in, filter then top off with the fluid of your choice. (I say that because of the myriad of threads that people respond / post with in regards to the use of all kinds of different oils and their applications. If really dirty keep filling and flushig with the above prescribed method. Then enjoy!

is there a danger of trapping air in the system? is there an air bleeding procedure?

approximately how much fluid does the whole thing hold?

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Ben
1987 190d 2.5Turbo

I think under normal circumstances it will bleed itself naturally but I'm not sure. I use generic parts store "power steering fluid" labeled as such, not atf. There's an ongoing debate around here as to whether the standard dexron/mercon III atf disintegrates seals in the system or not. The "general" conclusion is "yes it does", or "I'm not saying I don't believe you but I've used it for 50,000 miles without any trouble" followed by "mine sprung a leak the week after I put it in." I avoided it all by just using labeled PSF. Mine had ATF in it prior to my changing it (years ago) and ever since then, it seems to keep turning back to the ATF color in spite of my always replenishing with clear-ish fluid. I'm surprised it has that much left over but I guess anything's possible. If it's actually the pump disintegrating or something I'll just wait for it to fail. I've got a leak in a hose somewhere; the level will stay filled properly for literally weeks and then one day I'll start the car the day after it was fine and the thing will make groaning noises every time I turn the wheel, and when I start filling from the quart I always carry in the trunk, I find it just about down to the filter. Refill, and it's good for another random period of time.

I've never found min-max marks. I just fill to within an inch or so of the top and figure it's going to leak out anyway. I don't think it makes much difference. As long as 1) the fluid covers the inlet at all times, and 2) it's not so full that it can't ever return fluid to the reservoir -- I think it's irrelevant exactly how much is in there.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Others have changed by running the car with the return line in a jug, helper pouring fluid into the reservoir until the return comes out clean (while turning the wheels).

I've done the reservoir and filter only method, because it's easier (albeit less complete).

I believe that the max mark is on the plastic piece in the center.

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Gone to the dark side

- Jeff

http://www.peachparts.com/Wikka/PsFluidFlush

Did this on my 300SD and took all of 15 minutes. That old stuff was nasty!
As a plus, i don't have any groans from the ps pump anymore. I just used generic ps fluid...FWIW.

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----Adam

1985 300SD 322,000

No danger of getting air in the system, it is self bleeding. The fluid level at operating temp. is 1 1/4" to 1 1/2" from the top of the reservoir, that is where the mim, max would be, if your pump had that plastic sleeve.