Uh oh. Put power steering fluid in hydraulic reservoir! - Benzworld.org

C + A · 08-22-2005, 06:52 PM

Hello All:

Okay, I subscribed to AllDataDIY, read up as much as I could on the W140's power steering system, then accidentally filled the hydraulic fluid resevoir with the MB power steering fluid, thinking that was the right reservoir. About five minutes later, I noticed the ACTUAL power steering reservoir, which was low, and topped it off.

Now I've got around 500 ml of power steering fluid mixed in with the hydraulic fluid. Am I screwed? What effect, if any, will my mistake make? Should I bleed the hydraulic system and re-fill it with the proper fluid?

I feel pretty dumb, but I really thought I knew what I was doing. Guess I only knew enough to be dangerous!

Any guidance from you chaps would be welcomed.

93 BENZ S400SEL · 08-22-2005, 10:42 PM

What do you mean by hydraulic fluid reservoir? Brake fluid?
PGP

C + A · 08-22-2005, 11:43 PM

Under the plastic cowling on the USA driver's side behind the headlight is a small removable access panel. Opening it up reveals a reservoir with a dipstick in the cap. The label on the top says "Hydraulic Oil." I believe this is where the excess fluid from the self leveling ride height system goes, after just now finding pictures from Merc600sec showing his work with that system.

My concern is that the 500 ml of power steering fluide that is now in that self leveling system will have an adverse effect on the accumulators or something.

Any thoughts or advice?

93 BENZ S400SEL · 08-23-2005, 08:53 AM

Sorry I did not know that as I dont have self leveling system on my car. What is the difference betwen the 2 fluids.A MB dealer parts department that sells the fluids should know.
They may be similar chemically. If not do a Google on both fluids to see the composition.
PGP

pcmaher · 08-23-2005, 09:25 PM

My gut tells me it won't matter. It would be worth a call to a dealer to see if the two oils are similar in composition. I know the suspension oil is Mineral oil based.

C + A · 08-23-2005, 11:01 PM

pcmaher:

Okay, good idea. Thanks!

Earlier today, I purchased some of the hydraulic fluid that is SUPPPOSED to go in that reservoir to compare it with the power steering fluid. The hydraulic fluid is slightly less dense, and lighter in colour than the power steering fluid, but they seemed to have a mostly similar feel.

The hydraulic fluid looks pretty dark, which makes me think it's probably going to want to be flushed pretty soon anyway. I'll be closely reading through the posts regarding accumulators and ride leveling when that time comes.

Thanks again for helping; I appreciate your gut reaction!

[:)]

pcmaher · 08-24-2005, 06:29 AM

Hmmm, if you're hydraulic fluid is dark, it could indicate a problem. How is the ride? Nice and smooth, or harsh? I would flush it in any case. You should read my page on the suspension system to get an understanding of how the rear system works. Click on the link to my webpage under my signature, and got to Projects, ADS Diagnosis. Also, Merc600sec has good photos in his gallery...

http://www.mbnz.org/gallery/showlink.asp?parentid=34&catid=12252&subname=Self% 20Levelling%20bits

Another post that may help...

http://www.mbnz.org/forums/forums/thread-view.asp?tid=1183017&posts=3&hl=

C + A · 08-24-2005, 05:53 PM

Thanks for your guidance.

I was wondering about the relative darkness of the hydraulic fluid. The ride seems fine, apart from the fact that the previous owner put 20" Momo rims and Pirelli ZR low profile tires on the car. It's a pretty "sporty" ride compared with the stock tires and rims on another S class I've driven, but doesn't feel uncomfortable (yet).

I'll read up on the instructions you've provided in your profile section, and the other link you suggested. Thanks again for contributing so much to this forum, pcmaher. Your thoroughness and shared knowledge are much appreciated!

[:)]