Author Topic: Another 6.9 that wont raise (diagnostic tips)  (Read 785 times)

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #15 on: 17 May 2020, 05:47 PM »
Alright,

Took the selector apart, pulled the balls, and left the rods in because I was afraid to go further. I did get the rods to move one way and the other, but they felt a bit sticky.

Re-assembled it all.

Started it up... and still no discernible detents other than a very faint click on one position... no rise.

do I try this all again with the car on jacks?
1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

daantjie

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #16 on: 17 May 2020, 06:47 PM »
Putting the car on jacks is not the answer to get "pump up" as the car has to be "down" for the leveling valves to be in the "filling" position.  Basically with a healthy system, with the car fully down to the ground, upon starting the motor you should see the car rise at both axles after about 20-30 seconds of idling only, no revving should be needed on a good system.  You will see the car rise slowly at first, and then more rapidly towards the end until it settles in the normal driving position.

This might be a dumb question, but are you sure your tank is filled to proper level?  I must ask as often we overlook the simple things ;D

When the car is running, do you see a slow trickle of fluid coming back into the tank via the main filter under the pressure regulator?  You will likely need a strong flashlight to see it but if the system has pressureized (cut over pressure) then the fluid is cycled back into the tank.  One more thing to check is to see if all your lines are hooked up properly.  The main one which you need to check for starters is the connections to the main accumulator, or the "5th sphere", this is the 2nd one in the driver side wheel well.  There needs to be one line into it, and one line out, and they must be connected to the pertinent connections on the both the pressure regulator and the height control switch.  Might be time to take a hard look at the service manual for the hard line connections, one never knows if someone before you monkeyed with the system and messed things up ???
Daniel
1977 450 SEL 6.9 - Astralsilber

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #17 on: 17 May 2020, 07:00 PM »
I would assume the engineers at MB designed the system to pump itself up from dead flat, so I should assume a healthy system can do this.

The tank is almost full to the top, I assumed this was normal and haven't added or subtracted fluid. Should there be less?

As far as the main one, is that the one with the switch on it? I can take a picture of how it's connected, but considering the sphere had overspray from a previous repaint, I'm assuming that it was working when all of that was hooked up, and I re-connected it all the same.

1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

daantjie

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #18 on: 17 May 2020, 09:02 PM »
OK you need to suck out some fluid then, the tank should not be that full, though I am not sure if it will cause a "no rise" condition, but regardless, you need to only fill it as per the marks on the dipstick, there should be a gap between the bottom of the filter and the top of the fluid.

If you look at the service manual here are the "B" lines:

B1 - High pressure feed from the pump into the pressure regulator
B2 - Line from the pressure regulator to the 5th sphere (the one with the pressure sensor on top which activates the warning lamp on dash)
B3 - Line from 5th sphere to the height control switch - connects at the bottom of the switch
B4 - Line from height control switch to the level control valves - connects at the firewall side of the height control switch with the switch in situ
B5 - Line to the accumulators from the level control valves
B6 - Hose to the struts from the accumulators
Daniel
1977 450 SEL 6.9 - Astralsilber

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #19 on: 17 May 2020, 09:05 PM »
There are two lines. I assume i fill to line 2? I guess ill use the pump to empty it :-).

Where can i find the manual?
1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

daantjie

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #20 on: 17 May 2020, 09:13 PM »
Check out the Library on the site, it should all be under "Chassis and Body" under section "32"

Just filling to the first line is fine.  It can be a bit tricky to read the fluid as it is very thin.
« Last Edit: 17 May 2020, 09:19 PM by daantjie »
Daniel
1977 450 SEL 6.9 - Astralsilber

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #21 on: 18 May 2020, 05:04 AM »
Got it,

Geting the level right will be a nice start, the fluid is a little dark at the corners, so I will also have to replace the rubber lines. I'd like to diagnose the issues first.

If its a pump, is there a reputable rebuilder, or do I have to buy a new one, or suggestions?
1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

rumb

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #22 on: 18 May 2020, 05:23 AM »
I'd like to reiterate that the height valves have an operating range. If the car is completely flat it will be past the fill range. The car has to be raised some to get the valve in the operating range. Look at the lever on it. It should not be more than about 30 degrees up, or is it down, cant remember. If further the passage ways inside are blocked off and no fluid will pass.

Rebuilding pump yourself is not that hard.  The rear seal you can get from mercedes.  The orings you can buy for cheap. Mercedesource sells an overpriced kit.  If the inside of the body is scored it will never reseal. Some instructions say to gently heat the body to extract the internal part. I found that sharply rapping it on wooden workbench works better.
I will post orings sizes later.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #23 on: 18 May 2020, 05:28 AM »
This is great info thank you. I think i need to order some extra copper crush washers as my local napa doesnt have em all
1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #24 on: 18 May 2020, 07:27 PM »
Fill is all the way up, which is where the front lever is. I can detach the leveling rod and try to move to to neutral, but I would imagine a healthy pump can work with the "fill" position.

I ordered a used "working" pump. And while I know its a mistake to order used parts, I also ordered seals. If both don't work, I'll send it for rebuild at C&M Hydraulics as they're a state over.

Am I mistaken that the pump is relatively easy to replace? It seems to be "right there"

Oh...and one more thing. I ordered a power steering filter and reservoir filter. But I get a bunch out the top of the cap where the nut sits. is there a trick to these?

Thanks for all the advice so far.


1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

daantjie

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #25 on: 18 May 2020, 08:38 PM »
To remove the pump is not too hard, however make sure you get a good bite on the 4x hex head bolts, so make sure to clean them out well before you introduce the hex bit.  You will see 6x bolts but 2 of them hold the cap and the other 4 are through bolts to hold the pump to the engine.

Also take note of the "drive disk" between the pump and the drive sprocket which is driven off the timing chain.

Make sure you also order the paper gasket, I used some Permatex "Aviation form a gasket" with the paper gasket to get a better seal, but that is just a habit of mine with paper gaskets, use it, don't use it, up to you.
Daniel
1977 450 SEL 6.9 - Astralsilber

john erbe

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #26 on: 19 May 2020, 10:46 AM »
When you attempt again and it wont raise, put a block like a 2x4 under the driver's side front wheel. For whatever the mysterious reason that used to work for me.

secondslc

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #27 on: 19 May 2020, 11:42 AM »
sheesh if its that easy I’ll try it after work!

1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

rumb

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #28 on: 19 May 2020, 12:28 PM »
When you attempt again and it wont raise, put a block like a 2x4 under the driver's side front wheel. For whatever the mysterious reason that used to work for me.

That will put the leveler valve back into the operating range that I have mentioned.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Punker

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Re: Another 6.9 that wont raise (diagnostic tips)
« Reply #29 on: 19 May 2020, 12:48 PM »
What does the pressure control light say? It should light up during start and go out after a few seconds. When it goes out a pressure of at least 100 bar is reached. If it lights up permanently, the system pressure has not been reached,

By the way, all the lines on my control valve were mixed up.

Greetings
1978 Mercedes 6.9 # 4616 - black/black leather
BMW R 25/3