Low pressure, 79 6.9

[gs sparhawk]

The dash light glows some--not bright. low pressure?? Any checks to verify outside of putting a gauge in line. Can do that if necessary.. Car goes up & down with the leveler valve change & stays up. Maybe "If it ain't broke, don't fix it"??

Sparky

[diametricalbenz]

The light will stay on if in any other position (locked or raised) other than fully depressed (self levelling). If it's fully depressed with the light still on then that's not normal function of the light indicator.

[gs sparhawk]

So, can I suppose that it is the light or pressure switch that is not right ----or??---the less palatable conclusion that the pump is tired or the regulator spring is getting weak??

The car goes up OK, so I am presuming that the function of the suspension is the only thing that really matters. I put a new master reservoir and left wheel reservoir in. The ride is improving with each repair but not there yet.
I previously mentioned the changeout of the master and found the bladder gone in the left front also. I can see that, over time, they will all get checked. It is fairly simple to disconnect the center fitting and put a straw into the sphere and see how far in it goes. If it goes to the bottom, it's gone. I notice that the new ones have the bladder right up to the female fitting before installation and I doubt that it would be very much depressed after use and the hose disconnected. Easy to check without totally dismounting. The most irritating issue is getting to all three of the mounting nuts. flex socket is very helpful. MUST use the flare nut wrench on the fittings, though.

Oh, yes, if one simply accepts the fact that one will get hydraulic oil all over themselves, it is less irritating on the nerves.

Sparky

[diametricalbenz]

The pump may be getting tired. It is supposed to be working at 2100-2900psi.

I applaud you on delving into this...hydraulic fluid everywhere included.

[gs sparhawk]

Don't I recall a repair kit mentioned for the pump? Seems like a much better option than a bazillion bucks to MB.

Sparky

[alabbasi]

You can find those suspension pumps on 300TD's and a couple of other models in the junk yard for not a lot. I bought one for $35 on half price Wednesday which came in handy.

[gs sparhawk]

Thank, Al. I'll keep my eyes peeled for one. Even if I really don't need one now, the future is uncertain and I'm still replacing reservoirs. Who knows what is next. Even w/new reservoirs, this car will still not owe me a thing.
Eagerly awaiting that 116-6.9 ride, though.

Sparky

[mercmad6.3]

Before messing with anything remember one thing, pump kits DO NOT WORK!

Next check the cable is pushing home ,the switch for the light is behind the dash and if the engine end of the cable on top of the reservoir is sticking ( very common problem) the cable won't be going home properly.
To undo the cable on the reservoir,undo the circlip on top of the cable don't touch the nut.
Clean the exposed end of the cable with some fine sand paper and spray some teflon spray on the end while getting some one to work the cable in and out.It should be smooth and easy to use without any resistance.

Get better advice here.. www.m-100.cc

[Pooka]

These pumps are only available new and they run about $1050. The pump from the station wagon 123 (from what I have heard) will not put up enough pressure. 2900 PSI is quite a bit. And Mercedes does not sell a rebuild kit.

There is an alternative. These are vane pumps are are simple to rebuild. Just take photos of everything when you are taking it apart so you can put it back in the same way. It is possible to reverse the rotation on these so be carefull.

Take the pump to anyplace that rebuilds hydraulic equipment and see if they can rebuild it for you. Vane pumps are VERY easy to rebuild. All you need are some new vanes and a new inner race. Any good hydraulic repair shop could do this for a lot less than the price of a new one.

I do not know the OEM of this pump and I am sure Mercedes did not build it. If you do this then please post what you find.

Pooka

[mercmad6.3]

The pump is the only one mercedes make. It's fitted to, not only the hydro cars 116-036 and 126-036 but All of the self levelling cars.
The only other pump they made was for the W114 when was first released and is no longer available. The kits are $36 and you can buy them from any mercedes dealer.
The pumps can pump to 5000 PSi without any problem.
The pumps are not easy to rebuild,they are not a vane pump but a rotary piston pump,there's no vanes in there. Once you have removed the inner rotating member you have destroyed the pump as it requires a special guide to fit the two parts back together and not damage the surface of the pump body and the inner seal.
The kit only consists of the lip seal for the drive and the seal for the outer cover.It's a genric mercedes product ,possibly out sourced as a lot of their parts are but who cares? I have done dozens of these things on all vmodels of mercedes So I have some idea of what it what.

[gs sparhawk]

Thanks for the advice. I do see in my 6.9 service addendum that the pumps are, indeed, the radial piston type and I will certainly, not take one apart. This one still supports the car very well. I do not trust the light. I glows partially and not brightly. besides, I am not riding on a 'light'. I am riding on pressure and I have enjough so far. Actually, the pump does not have to supply much volume, just enough to make up for leakage and the occasional cargo addition to the rear seat. It appears to be mostly employed in maintaining pressure to the main reservoir, from which the supply of necessary make-up oil goes to the other four reservoirs. If one studies the section and has a basic understanding of hydraulics, it is a well understood principle that is nicely employed, no magic. But, it does appear to have the ability call up from some owner/mechanics, certain select incantations.

One more sphere/reservoir and I think I'll be riding nicely, livin' large. Well----
---

Now looking at at two TDs, a '66 200D finnie, a 380 SE and a SD. Heck, I'll take 'em all. Got to keep the projects coming.

Sparky

[alabbasi]

Originally Posted by Pooka

The pump from the station wagon 123 (from what I have heard) will not put up enough pressure. 2900 PSI is quite a bit. And Mercedes does not sell a rebuild kit.

I pulled a pump from a wagon to fit to my 6.9. It works just fine. MB does not sell a rebuild kit but the do sell individual seals which may help.

[mercmad6.3]

Al,down here it's listed as kit,two rubber seals in a plastic bag..

Sparky,try bleeding the system before changing the sphere to see if the light goes out. Lift the car in the air so all four wheels are hanging down,pull the knob out as far as you can then run the car for 30 seconds to 1 minute at 2000 RPM. turn it off ,push the knob right home and gently lower the car back on it's wheels. Start the car and let it stabilise and see if the light goes out.
Have you changed the filter at all? .

[gs sparhawk]

yeah, I'll try the up and down move but I have had it every which way doing repairs underneath. The right front corner is hard. No spring whatsoever. Back goes up and down easily. Left front got very compliant after changing the sphere. Kind of like a crazy ride with one corner bad.

I'm not really worried about the pump right now since it goes up readily but the tips on the pump application are very good to have, Al. Thanks. I hope I won't need that bit of knowledge but I'll file it away. Of course, wagons seem almost as rare as the 6.9.

What I really need is the electric switch that screws into the top of the main sphere ---since I broke and welded mine----sitll holding, however. Mucho dinero. And, I'll get to the filter, as well. So many projects, sooo little time!

My biggest challenge is, really, where to keep the expanding family.

'77 230, 75 280, 78 & 80 300CDs, 77 300D sedan, 240Ds, 79 450 SEL 6.9. ( Maybe today, 79 DT), looking at others------------Addiction????? (You wouldn't think that I could find that many orphans in SD, would you?)

Al, you can be my sponsor since you will probably be the most sympathetic and have been to the meetings, I'd guess. ( Hello, I am Sparky, and I am a compulsive MB seeker---I am thankful for Al, who has been alert enough to see my pain and kind enough to support me in seeking help in my time of need.)

Finishing up an engine swap today in my Astrovan. I know, I know--but, it DOES have some metric fittings, if that is any consolation. At least, it is still, "lefty-loosey, righty-tighty".

Thanks, all, for the generous contributions to the common good. We lost a lot of 'community' when the internet came on the scene but we have generated a larger one, it seems, and I am grateful.

Sparky

[gs sparhawk]

Just changed the right front sphere. If I could get close to the engineer who decided how to mount this one, I rip his head off and spit in his neck. Had to remove the air pump to get to some nuts. Threw it away. It was frozen up tight & the belt was off anyway. And then, the pipe fittings. Oh yeah. I had to resort to favorite words to get through this contortionists nightmare. I've been wrenching for a little over 55 years (started when I was 15) and know a few tricks to get nuts & fittings off & on. Had to reach way back into the toolbox. It's a little below freezing and a bit past midnight and in the driveway is not the place to be but, damn, I'm done. Time to go take a ride .
These old bones will enjoy this evening's layout in the hot tub.

Back from the ride. the front is much nicer but the rear is still hard. Guess I'll hit up my connection again. Might as well go for the last two & get it over with. Then, exhaust, straighten up the cc, etc etc--------

Sparky