More info on the hydro pneumatic system problems

Thanks to all for the response regarding my 1984 500SEL and it hydro pneumatic system problems. Heres a little history to answer some of your questions. It has the full system front and rear.When I first bought the car
It would slowly lower if it sat idle for over as week, after about three months it started lowering if it sat for a couple of days, which was not that bad of a problem because as soon as i started it up it would immediately would lift and off I would go, then it became a daily thing and the time between when I stated it and when the pump would engage became longer. About that time the ride began getting firm....Very firm!. I don't know if this has any thing to do with it or not but my a/c fan stopped at around the same time, (I didn't know if the a/c and the hydro pneumatic system used the same relay or something electrical). .And now it will not lift at all. Even though I would like to diagnose and fix it myself I realize that if i do take it to a repair shop I will at least be able to speak intelligently, because up until now all I get is "ya gotta replace the whole system" to the tune of $4000.00 plus
Thanks for the help, Dan
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Could it be belts that failed? You mentioned air-conditioning failing at about same time.
Danno wrote:

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car
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You have a leak which has gotten progressively worse over time. Check the reservior - it's probably empty by now and you're running your pump dry (not good). Park the car somewhere clean, re-fill the reservior, start it up and watch underneath the car for leaks as the system pressurizes. If the system is full of air, this could take a while. Keep watching the level in the reservior and top it off as it goes down (the system will self-bleed). My first thought was the accumulators, but they usually go bad suddenly. Still, if no leak is apparent by a puddle under the car, I suppose it's still a possibility. If that's the case, your fluid will eventually stop disappearing, but your ride will remain very hard.
Bill Balmer 1986 190E 2.3-16
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Cossie wrote:

Hi Bill, Do you happen to know which type of fluid to fill the reservior with? Is it standard hydraulic fluid, or some special type of fluid for this application?
And what are accumulators? Do you have any links to point me to where I could read about them? I just want to get my car riding smooth again. The motor still runs like a young horse, even after 515 tkm, and with the suspension back in shape this car will last me at least 5 more years.
Thanks, Mike
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First, I should qualify my answers with the caveat that they apply to my car. Exactly how the hydropneumatic SLS on your car differs, I don't know, but I believe it is at least similar.
I have always used the hydraulic fluid from the dealer. I don't know if it's different from standard, run-of-the-mill hydraulic fluid in any way. But be careful of what they charge you for it. I bought some from my local dealer at $14/liter, which I thought was kind of high. Several months later (when the other accumulator went out on me) I went back for more and they gave me a price of $42/liter! I complained, telling them that I had gotten it for $14 just a few months back, and without blinking, the parts guy said, "Okay, I'll give it to you for $14." I was happy to get the "low" price, but it made me wonder if he had just pulled the $42 number out of thin air, thinking I was one of his rich, money-no-object customers who wouldn't question it. I'm not.
Accumulators are known by several other names: nitrogen cells, air cells, coconuts. They are spherical (on my car - I've also seen illustrations of a semi-cylindrical shape) and they are mounted under the car inboard of each wheel. They have a diaphragm in the middle. On one side is hydraulic fluid which runs to the shock (damper). On the other side of the diaphragm is nitrogen in gas form, which compresses and expands in relation to the motion of the damper. When the diaphragm ruptures, the whole accumulator fills with hydraulic fluid, negating any damping and making the ride very non-compliant (hard as a rock).
I have replaced both accumulators on my car (it only has SLS in the rear), and it's a pretty easy job. Three bolts to remove the accumulator from a bracket, and some line wrenches to disconnect the hydraulic lines is all you need. After the new accumulator(s) is installed, you just have to fill the reservior, start the car, and keep filling it up until the level stops dropping. The system self-bleeds. Then keep an eye on it for the next few drives, as the level may drop more as the car goes through some compression/expansion cycles.
I got my accumulators from The Benz Bin online. Their service stinks and they usually screw up my order, but their prices are good. The dealer wanted around $200 for each, and I got them for $71, as I recall. Worth the hassle, especially if you're buying two.
Bill Balmer 1986 190E 2.3-16 first 16V in the US featured in Car & Driver - March, 1986
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Cossie wrote:

Thank you for your very detailed answer and explanation. Now I am armed with enough knowledge to fix my car.
-- mike
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Correct me if I'm wrong but I thought hydraulic fluid for MB suspensions was a formulation unique to Mercedes; nothing else works properly.
Again relying on poor memory I think John Olson of the SL Market Letter sells the stuff cheaper than anybody. I might be making that up out of thin air though; check.

They show as $86 on http://parts.mbz.org ; call them and say you want BenzBins price and before he says yes or no start reading off your credit card number. Greed kicks in and you'll get them. The service won't stink and you'll be talking to somebody that actually knows the car not some high school kid that was selling shoes in Wal Mart last summer.
--
OEM parts - Benz: http://parts.mbz.org BMW: http://buyeuroparts.com
http://www.mbz.org | Mailing lists: http://lists.mbz.org
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Danno wrote:

Hi, I have a 1985 500 SEL (with 515 thousand kilometers) and over the past three years I have experienced exactly the same situation that you describe.
I hope that there is something that I can do to fix it. Let me know if you figure anything out.
-- mike
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