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6.9 suspension problems - 6.9 newbie here

Started by s class, 05 September 2007, 04:31 PM

s class

THanks for all the help guys,

The short version of the story is my new front struts arrive next week from Germany, the new spheres a few days later from Autohaus.


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class



[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class

Futher progress - today I removed the suspension pump and stripped it.  I think I know where a lot of the pressure has been going -



THis picture shows the back of the pump.  It had a non-standard seal installed (the black one in the picture)  the other seal is a new MB replacement.  What is tough to see is that the back of the pump had been machined out to about 1mm larger diameter to fit the generic black seal.  This has had 2 consequences :

a) the port which you see at 12 o clock in the seal seat was now blocked off.  What is this port for?

b) the seal was only a loose fit around the shaft.  I could see daylight between them.   :o

So - it must have been leaking into the engine like crazy.  Is that rear seal subjected to the full suspension pressure, or only some 'ambient' pressure in the pump?

Progress... Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

CraigS

Is the one you found off the 420 a direct bolt on ? If so, why spend time on this one ?
[url="http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/"]http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/[/url]

s class

The 420 item is a direct replacement.  When I got the original pump off, the seal looked odd, so I cleaned it up to investigate.  I'm glad I did because it has given me some confidence in the various diagnoses of the problems that have been made. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

oscar

Quote from: s class on 18 September 2007, 01:48 PM
What is tough to see is that the back of the pump had been machined out to about 1mm larger diameter to fit the generic black seal.  This has had 2 consequences :

a) the port which you see at 12 o clock in the seal seat was now blocked off.  What is this port for?

b) the seal was only a loose fit around the shaft.  I could see daylight between them.   :o

So - it must have been leaking into the engine like crazy.  Is that rear seal subjected to the full suspension pressure, or only some 'ambient' pressure in the pump?

Nice struts :)

a) Searching thru my pics my original pump had two half seals INA brand I think, placed back to back or (front to front) and would've obscured that port somewhat too.  This pic has the rubber of the seals picked out but with the metal outer lips remnants intact.  I never took a photo of them removed but I'm sure that port was visible afterwards.




b)  With the pump together and the outlet plugged with a finger, I could blow in the inlet and air escaped between shaft and seal.

The replacement seal fixed everything and is exactly like the one you picture on the left.   I put the seal in upside down to how yours is pictured so the metal lip faces up not down. 

Is it subject to full pressure? Not sure.  Personally I think yes or just about due to the amount of oil I was losing through two separate pumps.  The second one I couldn't blow air past the seal.  Maybe from that port you pictured comes full pressure oil.  I think the shaft has an oil "tunnel","pipe" for want of a better term.  Whether it acts as a return or simply passively helps to lubricate the bushes etc, I dunno.
1973 350SE, my first & fave

koan


The seal on the back of the pump, there is only one but it is  a "special double lip seal" is on the inlet side of the pump and therefore is not under pressure. When it fails suspension fluid is sucked into the engine.

koan
Boogity, Boogity, Boogity, Amen!

oscar

Quote from: koan on 18 September 2007, 04:37 PM
When it fails suspension fluid is sucked into the engine.

I had doubts Koan so I pulled a spare apart, plugged holes, blew thru passages, tried a few combinations and found that, you're absolutely right.  ;) 

I do have a question though, how much suction does the crankcase produce?  I never knew it produced any.  Is it slight or strong?

Basically, that little hole that sclass pictures that puts oil into the section where the rear seal is, is open to the low pressure area of the pump that supplies the pistons. The oil flows into the round crevice highlighted in the second picture by the yellow line.

Here's a pic of that supply hole to compare with sclass' pic


The hole opens to this crevice


More pics here of the pump dissassembled as far as I would dare - has pics of the seal and pistons removed plus shaft http://gallery.w116.org/v/garage/oscars/suspension+pump/

Also, re the double lip seal, I agree that is what is required to reseal the pump.  However, just how someone found a substitute for sclass' pump, my original pump had two single lip seals back to back.  INA brand G 15*23*3 part numbers.  No idea if that's what was in early pumps or someone resealed it with them but a new double lip seal has been on for a year or more in the same pump and it's working a treat.
There's a pic of the said single lip type although torn apart here http://img138.imageshack.us/img138/1900/hydro5mediumqh6.jpg
1973 350SE, my first & fave

koan

Quote from: oscar on 19 September 2007, 06:50 PM

I do have a question though, how much suction does the crankcase produce?  I never knew it produced any.  Is it slight or strong?


The suction comes from the Positive Crankcase Ventilation (PCV) setup. On my engine  clean air from the air filter goes into the valve cover on one side and is drawn off the other cover by a connection to a small orifice near the idle speed screw.
Boogity, Boogity, Boogity, Amen!

s class

Quote from: oscar on 18 September 2007, 04:26 PM
The replacement seal fixed everything and is exactly like the one you picture on the left.   I put the seal in upside down to how yours is pictured so the metal lip faces up not down. 

That is how I understand it is supposed to be. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class

Annoying delay - I have only received one front strut, the one pictured above.  The other one has not arrived yet.  I queried it at the dealer, and the answer from Germany is that there is no stock.  They are awaiting production, and I will get it in late October. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

CraigS

How is that going to sit with the authorities ? Does that give you any form of "out" if you have, or can get, a letter from DC advising that there is no stock ? Puts the 21 days a little out of reach doesn't it.
[url="http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/"]http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/[/url]

s class

21 days has come and gone, I'm into penalties already.  Its one of those things.  And no they are not understanding.  No letter is going to help. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class

Update - I'm duplicating some info that I put in another thread, to tie it all together here :

Today I fitted the 'new' suspension pump, and the next job is to remove the suspension oil tank.  I'm not clear though on how to get it out.  Do I need to disconnect all (5 or so) hydro lines from the valve assembly?  I will also replace the hoses under the tank. 

I have not ordered rear struts, as I would like to still do the leak test before going ahead with that.  The rear struts are not leaking externally, and the rear of the car does not sink overnight, so I had thought they may be OK. 

As to the other items related to the suspension, I'm fitting new upper control arms in the front because they are desperate.  In time I will be replacing the bushes in the front lower control arms and rear trailing arms.  I don't believe I need to do that before the inspection, so I'm leaving it for the time being, as I would like to do that properly, and two-pack paint all the suspension components. 

Here's some pics of the suspension pump mounting flange, and the pump internals for those who haven't seen one. 





[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

CraigS

I assume by this it means to return the car to the ground, and push the suspension knob back to the low driving position.

Quote from: styria on 26 September 2007, 01:40 PM

5. Carefully lower car back onto ground to driving position.

[url="http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/"]http://s109.photobucket.com/albums/n77/Aegeanfoods/My%20Cars/[/url]