Reccomended Steering Fluid - PeachParts Mercedes-Benz Forum

willw · #1 10-18-2012, 02:28 PM

Hello All,

Quick question, I'm replacing the steering pump filter in my 1984 300SD
federal this weekend. I have no leaks in the system, but I do have a
slight growl when I turn the wheel. My last car had a much worse problem
that I solved with changing the filter, so I'm hoping this will do the trick.

I searched the forum to see what the consensus was on what fluid to use
to replace the current fluid with, but I can't find a definitive answer. I
don't have the owners manual, just the Ebay CD, and the CD is hard to
figure out :-)

So, does anyone have a favorite fluid?

Thanks
Will W

sleepstar · #2 10-18-2012, 02:49 PM

i just use regular power steering fluid. i've had no problems.

Graplr · #3 10-18-2012, 03:02 PM

There is not a definitive answer. From the factory our cars had ATF in the power steering pump. Since then Mercedes has switched to using power steering fluid in their pumps. Some state the additives in modern ATF are not good for our pumps.

I use ATF in mine. I don't think it is too big of a deal which ever you want to use. If you choose to switch to power steering fluid I would completely drain the pump and steering box and flush them otherwise I would stick with ATF.

scottmcphee · #4 10-18-2012, 03:17 PM

ATF DexIII, same as in the tranny.

willw · #5 10-18-2012, 03:58 PM

Thanks for the info!

I don't know what's in the system now, so I think I'll drain it and
fill with regular ATF fluid. That way I have less clutter around the
garage :-)

PackerEdgerton · #6 10-18-2012, 07:46 PM

The owners' manual for my 83 240D calls for ATF. I have flushed and filled with ATF, swapped out the filter, it seems very happy. It has no malfunction or strange noises, so I didn't add anything to the ATF during the R&R maintenance.

For my wife's mini-van (making growling/squeaking noises in the power steering), I swapped out all the power steering fluid with new fluid and then added about 20% Marvel Mystery Oil (MMO) by volume.

The noise immediately went away, and there are no leaks. Everything else seems to be normal.

Sincerely,

Packman

My research noted that MMO is composed of:

70% Light Aromatic Oil (Pale Oil)
- It is a Naphthenic Oil (as is power steering fluid), so while it oxidizes faster than a Paraffinic oil, it does clean and dissolve sludge and carbon well and cleans up after itself from any oxidation. serves as base oil as well. [Naphthenic oils have more solvency and are more polar (they are attracted to metal more), but oxidize faster.

29% Mineral Spirits
- Cleans Varnish very well. General cleaner. Also acts as an antioxidant.

38 parts per million (ppm) Boron
- AW/EP agent, friction reducer, antioxidant

900 ppm Phosporous
- AW/EP agent

1/2% 1, 2 ortho-Dichlorobenzene
- EP agent as it interacts with Iron to form an Iron chloride barrier under any ZDDP or other AW additives. Also very good cleaner/solvent, and friction reducer

1/4% 1, 4 para-Dichlorobenzene
- EP agent as it interacts with Iron to form an Iron chloride barrier under any ZDDP or other AW additives. Also very good cleaner/solvent, and friction reducer

Oil of wintergreen - for the scent
- Not just for the cent, is also a cleaner. may aid lubricity.

Red Dye - for the color
- well this one just colors the stuff

kingwanca · #7 10-20-2012, 02:07 PM

Never been a fan of Chemical Magic fixes, but can testify that the 1/2 VW I fly behind on my Airbike began running rough, Did a leakdown test, 1 cylinder was down at least 40-50 pounds, drained off 1 qt, put in 1 qt MMO, it holds about 3 qts. w/cooler.
Jumped in her and flew around the patch just in case........... she started to smooth out so I left the pattern, put a little over an hour on it and landed.
There had been a huge argument between a few of the guys at the field about MMO and snake-oil in general...................Leakdown in both cylinders was just below 200 psi.
Made a believer outta me, don;t know if a guide was sticking or rings varnished up or both, I just know what the leak down said, Andy

PackerEdgerton · #8 10-20-2012, 03:07 PM

In the case of the wife's minivan, I figured that the ultimate fix was a new power steering pump, and that if the MMO didn't work, then that would be the next step. It does appear that any varnish and/or gummed-up seals making the noise has been temporarily abated, with no loss in function, so I will wait to see how things pan out.

This was just my experiment based on my theory of what was causing the noise, and also checking with the MMO forum (got an answer from an MMO technical expert) before proceeding. The fact that MMO is 70% Light Aromatic Oil (Pale Oil)
(A Naphthenic Oil as is power steering fluid) info came from them.

Anyway, drove the van the other day, noise if 99% gone, and everything seems fine.

Sincerely,

Packman

JHZR2 · #9 10-20-2012, 04:45 PM

Ive found the MB PSF to be fairly well priced from some dealers... $5ish.

torsionbar · #10 10-21-2012, 09:56 PM

I've always used genuine mb ps fluid. it isn't expensive and you know it'll work. better than mystery fluid imo.

PackerEdgerton · #11 10-22-2012, 01:29 AM

Quote:

Originally Posted by torsionbar

I've always used genuine mb ps fluid. it isn't expensive and you know it'll work. better than mystery fluid imo.

Hang on here. He's asking about a W123. My owner's manual specifically calls for ATF. Why go and buy MB PS fluid if the original manual calls for ATF?

If he didn't have a problem with noise, then I would not suggest the MMO. However, I am just saying that it worked for me, and seems to have no ill effects. If he has no issue, then it isn't needed.

Packman.

JHZR2 · #12 10-22-2012, 08:51 AM

What is interesting to me is that no w123 car ive ever owned has ever come to me with red ATF in the PS.

PSF is likely undyed ATF, but I've just never seen ATF in use in w123s!

I don't really care one way or another, and PSF works, as I'm sure ATF does too. ATF does have the benefit of many synthetic variants...

qwerty · #13 10-22-2012, 10:03 AM

Quote:

Originally Posted by JHZR2

What is interesting to me is that no w123 car ive ever owned has ever come to me with red ATF in the PS.

Interesting to you, perhaps.

A data point for everyone else? Not hardly.

Quote:

Originally Posted by JHZR2

...but I've just never seen ATF in use in w123s!

Have you ever seen a W123 owners manual that called for anything but ATF?

Quote:

Originally Posted by JHZR2

PSF is likely undyed ATF...

I am sure that you have never seen any, but some brands of power steering fluid are dyed. Some is even red, just like ATF.

qwerty · #14 10-22-2012, 10:16 AM

Quote:

Originally Posted by PackerEdgerton

Hang on here. He's asking about a W123.

Except that a 1984 300SD is not a W123.

JHZR2 · #15 10-22-2012, 11:38 AM

Quote:

Originally Posted by qwerty

Interesting to you, perhaps.

A data point for everyone else? Not hardly.

Have you ever seen a W123 owners manual that called for anything but ATF?

I am sure that you have never seen any, but some brands of power steering fluid are dyed. Some is even red, just like ATF.

Are you being a troll or just argumentitive? Does my experience with multiple, DEALER maintained MB diesel cars with substantial records from new (my criteria for purchase) have no value?

Why dont you go check the MB Bevo site? There it clearly calls out MB 236.3 as steering gear oil. While there are some ATFs listed on there, none carry ubiquitous specifications (Dex, merc, type A, type F, etc) that you would be buying off the shelf. Manuals listed ATF for power steering. Note the bevo title below. They also list 236.2, which isn't an AT fluid for their transmissions, or per bevo, 236.3, which carries the correct nomenclature to older manuals.

MB 236.3 - Steering gear oils (ATF, Specification 236.3) - Mercedes-Benz Specifications for Operating Fluids

And while over there, check out sheet 231.1, which shows clearly on Page 3-4 that fluid 236.3 is NOT used as an ATF in MB transmissions, and is a purpose-specific steering fluid. There is no instance where 236.3 is used in ATs.

http://bevo.mercedes-benz.com/d/d/en/Spec_231_1.pdf

So if you want to go by the book, the ATF you are selecting may be wrong!

So why not go back and re-read exactly what I said:

Quote:

What is interesting to me is that no w123 car ive ever owned has ever come to me with red ATF in the PS.

PSF is likely undyed ATF, but I've just never seen ATF in use in w123s!

I don't really care one way or another, and PSF works, as I'm sure ATF does too. ATF does have the benefit of many synthetic variants...

Which is consistent with the sheets that Ive linked to.

Now, the 1997 startek guide that is out there (which doesnt list w123 or w126 cars) says that BQ 1 46 0001 is the PS fluid, and that is what people are saying that they use from the dealer, which is a 236.3 fluid.

It does say that an approved Dex III can be used on that document (not stated specifically for 123/126), but remember that there is no Dex III on sheet 236.3. Others on here have stated that leaks have occurred when running ATF (nondescript, so likely Dex III) if you do searches for it. Ive been reading about this since 2002, so something that may be "interesting to me" is still highly relevant.

So go back to what I said.