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BigPimpin 08-13-2001 11:21 PM

Power steering fluid
My '88 420SEL is VERY slowly leaking power steering fluid, it starts to groan when I turn the wheels every two or three months or so. My mechanic installed a kit to stop the leaking, but I almost doubt that he did anything, because the problem's come back.

Anyway, my question is, is the a serious problem, or should I just keep adding fluid as needed? And, how do I know how much fluid there should be? I don't see any markings on the inside of the resevior (I don't really know what to call it). I bought MB power steering fluid, I just need to know how much to add. Thanks alot for any help.

Stan Pittman 08-13-2001 11:56 PM

You can just keep adding fluid if you don't mind the mess and it will be alright. It's not that expensive to reseal the pump or gear if thats what it takes to remedie the problem.

MikeTangas 08-14-2001 12:51 AM

Check the condition of your low pressure return hose. You may find that over the years the hose has begun to break down and is seeping the fluid through the hose. Do you have a fender well that is wet with steering fluid?

The return line on mine is held in place with small hose clamps, since it isn't a pressure line that is OK. I simply replaced the return line using 19/32 (I think??) crankcase ventilation line. Make sure the hose you use is rated for petroleum products, heater hose will not work.

Check the link for further details.

BigPimpin 08-14-2001 01:56 AM

Is it possible to add too much fluid though? Or should I just fill it to the top?

MikeTangas 08-14-2001 10:46 AM

There should be a mark or a line stamped into the body of the reservoir approximately 3/8 from the top. Fill to that line and you'll be full. Allow the level to drop too low and you will start sucking air into the system. If that happens the steering will make all sorts of noise and the fluid will appear pink and frothy.

BigPimpin 08-14-2001 12:47 PM

Thanks alot.

Marks88 08-14-2001 12:58 PM

Big Pimpin,

Don't want to ask the obvious, but has the P/S filter been changed? I had a similar problem on my 88 300E. Filter replacement and new fluid did the trick.


BigPimpin 08-14-2001 09:59 PM

I assumed that was done at the 120k mile service, but if it acts up again, I'll look into that. I added more fluid, and it works great now. Thanks.

MikeTangas 08-14-2001 11:40 PM

Now to locate where the fluid is going. Since replacing the return hose and resealing the gearbox last year I have not had to add one bit of steering fluid.

MikeF 08-15-2001 08:28 PM

OK. . .I changed my PS fluid last weekend and attempted to replace the filter. How do you get the %$*@* out? I unscrewed the stem/spring nut but it will not back off and it seems that the whole shaft just turns. I gave up.

Any ideas?


CJ 08-15-2001 08:38 PM

The filter lifts straight out.

David C Klasse 08-15-2001 09:05 PM

And as I recall, I had to use 2 screwdrivers to actually pull it out.

MikeTangas 08-15-2001 11:43 PM

At the bottom of the reservoir is a plate with a series of holes in it. That is the "steady plate". Just hook a small screwdriver or two into the holes and lift the plate straight up. The filter resides under the steay plate.

MikeF 08-16-2001 11:39 AM

I'm guessing we're talking about different setups. There is a shaft that runs up through the filter which has a white plastic sleeve which is about 1/2" in diameter. It is much bigger than the center hole in the filter. That sleeve rides on a spring that goes through the filter and into the nether regions of the ps pump. There is a small nut which is threaded onto the shaft that holds the sleeve and spring in place. This sleeve/spring is what places upward pressure on the reservoir lid. To put the lid on, you have to press down so that the cap nut will thread onto the shaft and enable the lid to seal to the reservoir. Does this make sense?

Essentially, there is no way to simply lift out the filter without removing the sleeve...and the entire shaft turns when I attempt to remove the nut holding the sleeve/spring in place.

Maybe I'm overlooking something obvious.


MikeTangas 08-16-2001 02:03 PM

OK. Mine has a steel sleeve over the spring, but it is not retained by any nut. Once the lid is off, the sleeve and spring simply pull up, then the steady plate etc. I cannot say if the 300E should have a nut retaining everythin inside. perhaps one of the E owners can chime in.

Have you owned the car since new? If not perhaps the PO added a little something extra to hold the innerds in place. Can you push down on the sleeve enough to see the unthreaded portion of the rod below the nut? If so, try to gently get on that portion with a small set of vise grips to hold the rod steady while removing the nut.

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