For older p/s pumps, roughly up to the mid-80's and/or with V-belt drive, some form of approved ATF is fine; with Mobil-1 probably being the preferred ATF. For newer pumps, I'm kind of changing my thinking back to Constantine's, especially on any car with the expensive dual-converter pump (most with SLS have this). The MB fluid might even be synthetic, for all we know - I haven't investigated that, but I know it's a little spendy at $7-$8 per bottle wholesale.
Now, for the SLS fluid (which goes to a different section of the same pump), you can NOT use ATF. That definitely requires special hydraulic fluid. Not a lot of cars have SLS, though - wagons, and a handful of later sedans, but that's about it. I guess it wasn't a very popular option for some reason. :) -dm > ------------------------------ > Date: Thu, 12 Jan 2006 21:33:34 -0500 > From: "Werner Fehlauer" <[EMAIL PROTECTED]> > Subject: Re: [MBZ] Power Steering pump failure. > > Constantine - I'll take the bait and argue your supposition that there is > some kind of "magic" engineering in Mercedes-Benz PS pumps that require > special "snake oil". > My '90 D has now gone for over 130,000 miles on ATF (put in by a major > dealer originally, and subsequently changed by me every 30k with Mobil1 > synthetic). No leaks, and no problems. I've also changed out the PS oil in > my daughter's '77 300D, my '84SD, and my '83SD. All work just fine. And > I'll live with the superior cold flow characteristics and high temperature > compatibility of Mobil1 any day over whatever dino oil they were thinking of > many years ago in Stuttgart. Sorry, but I just won't buy the argument that > some old Mercedes spec has to be followed, perhaps just because their > engineers either hadn't heard of Synthetic ATF or they hadn't personally > tested it first. > And Mobil1 will NOT cause O-rings and seals that normally are exposed to an > oil, to swell and leak as some urban legend will opine. > > Werner > > > ----- Original Message ----- > From: "Constantine N. Polites" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Thursday, January 12, 2006 4:16 PM > Subject: [MBZ] Power Steering pump failure. > > > >I just finished rebuilding my tandem pump. I sent part of the work out > > because I didn't have the right puller. > > The Vickers pumps made for MB require a special hydraulic oil. If you > > use ATF fluid, eventually there will be > > a failure both internally and externally. Internally, the "O" rings > > will swell and restrict flow. Externally, the main seal > > will deteriorate and you will have a leak. That leak will also keep the > > main bearing from being properly lubricated > > and again you will have a mechanical failure. I'd look first of all at > > the tiny "O" rings. If they are swollen replace them. > > > > Even though I did use the proper hydraulic oil, apparently the PO > > didn't. So I experienced the above conditions. > > > > This may have nothing to do with your conditions but it may help. > > > > Regards, > > Constantine
