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  #1  
Old 08-02-2011, 02:57 PM
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How long should 6.9 suspension stay raised after driving?

I don't own one, but depending on further research I might buy one in a couple years, so I was curious about this. How long should it take for the suspension to go all the way down after driving? Is it like a citroen where it takes less than an hour, or should it stay up longer than that? It seems like most of the pictures show them at driving ride height, which leads me to believe that the ones advertised as "runs and drives" but are flat on the ground in pictures probably need some expensive work. Also, is it true that you can swap normal springs into them? I know its losing part of the point of the car, but not all of them are worth the cost of fixing the suspension anymore and it would save them from pick and pull.
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  #2  
Old 08-02-2011, 08:52 PM
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It should never drop at all. 1/2" in cold weather over 24 hours is acceptable though. Unlike Citroens ,Mercedes have a 5th sphere which will maintain pressure.
No,Normal springs do not swap easily into them. The front spring mounts are missing a few bits and the weight of the engine soon kills the springs and the ride. It's better to go to the M100.cc site and check for cars that are for sale occasionally . That way you will pick up an enthusiast owned car in reasonable condition with plenty of online support from other owners.
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  #3  
Old 08-02-2011, 10:51 PM
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It's impossible for the system to stay permanently pressurized forever. Mine stays up for 2 weeks before the suspension is down.

Yes you can swap out the suspension for coil shock setup but you might as well buy a 450 and call it a day unless you have a lot of money you like to throw away.
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  #4  
Old 08-02-2011, 11:12 PM
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All of the 6.9's I have owned have never sunk. If yours is dropping in two weeks you have a leak.
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  #5  
Old 08-02-2011, 11:47 PM
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I have spent 2 years rebuilding my axle valves and main valve myself and it is true: car will stay for months if your axle valves are good. Car won't drop nor would you loose air pressure in the tank. This is the ideal world. If your car drops in weeks time your axle valves leak for sure. Time to rebuild the air suspension. Don't even think about changing to steel springs.
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Old 08-03-2011, 12:22 AM
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Hmm ok, I will keep that in mind if I ever plan to buy one. I have seen several sitting flat on the ground that are advertised as a running vehicle in good condition. I kinda had a feeling that wasn't normal. I wouldn't put steel springs in a nice one, but Id rather see one with normal suspension still on the road than going to the crusher pretty much complete like the only 6.9 I have ever seen in person.
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  #7  
Old 08-03-2011, 12:54 AM
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Quote:
Originally Posted by werminghausen View Post
I have spent 2 years rebuilding my axle valves and main valve myself and it is true: car will stay for months if your axle valves are good. Car won't drop nor would you loose air pressure in the tank. This is the ideal world. If your car drops in weeks time your axle valves leak for sure. Time to rebuild the air suspension. Don't even think about changing to steel springs.
Unlike the 109, the 6.9s are hydraulic - not air. Different system - but the case is the same, if the system drops it's indicative of a leak. I would not worry about dropping over the course of two weeks, but if it drops in two days, I'd be working on it if it were my car.
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  #8  
Old 08-03-2011, 07:12 AM
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6.9....sure hydraulic. Sorry, my fault.
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  #9  
Old 08-03-2011, 09:04 AM
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Quote:
Originally Posted by Travis_k View Post
I don't own one, but depending on further research I might buy one in a couple years, so I was curious about this. How long should it take for the suspension to go all the way down after driving? Is it like a citroen where it takes less than an hour, or should it stay up longer than that? It seems like most of the pictures show them at driving ride height, which leads me to believe that the ones advertised as "runs and drives" but are flat on the ground in pictures probably need some expensive work. Also, is it true that you can swap normal springs into them? I know its losing part of the point of the car, but not all of them are worth the cost of fixing the suspension anymore and it would save them from pick and pull.
If your Citroen goes down in a half hour, your system needs work.

My DS21 in the garage (old style LHS) has been up holding its own weight for six months.

The newer one I have (DS21 green fluid type) stays up about a day.
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  #10  
Old 08-04-2011, 12:38 AM
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Wink

Before condemning the whole 6.9 car for having lost it's support, it would be best to have a look around under the car and determine it's specific ailment.

It may even be essential to get a diagram of the system and become familiar with the functioning before even trying to evaluate the problem(s). If you can't do that just forget it. You'll screw it up even more trying to fix it. This is one MB that the lesser mechanically inclined should stay away from. Unless that person has some deep pockets. Thinking that you'll end up with the
"Super car" that it seems to promise is pie in the sky if it doesn't get completely done right and one will wish they never heard of it.

Otherwise, find that old 6.9 that is ready for the crusher because it is drooping and let ME buy it. I'm just an old fool with a few hundred to spare.

sparky
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  #11  
Old 08-04-2011, 01:06 AM
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What's the total cost involved in the rebuilding of one of these systems?
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  #12  
Old 08-04-2011, 06:49 AM
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Originally Posted by mercmad6.3 View Post
It should never drop at all. 1/2" in cold weather over 24 hours is acceptable though. Unlike Citroens ,Mercedes have a 5th sphere which will maintain pressure.
Citroens have two extra accumulators in addition to the four main spheres: one for the system and one for the brakes, so that the car stays up and can brake with the engine off.

Thus every Cit has a minimum of 6 spheres to maintaoin pressure for brakes and for the system.

Only Dave Burnham's special custom Cits might have anything else, that I know of. His cars are for things like ice boat racing and special trailers with more hydraulic needs.
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1953 220a project
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  #13  
Old 08-04-2011, 08:29 AM
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Quote:
Originally Posted by PanzerSD View Post
What's the total cost involved in the rebuilding of one of these systems?
The struts are about $1200 each, but they rarely go bad thankfully.

-J
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  #14  
Old 08-05-2011, 08:09 PM
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The system is dirt simple. A pump, struts and spheres as buffers. Last time I bought spheres they were around 125. Struts are high, I have heard there are different ones that work, but I replaced mine with an OEM set I picked up on a whim. The struts will leak, maybe just slightly, they still work fine but you will lose pressure. The spheres do nothing for keeping the system pressurized, they are just hydraulic buffers to keep your teeth from falling out.

I have my old struts, some say they can be rebuilt with new seals, but so far I have been unable to find a place to do it.

If anybody wants to try and rebuild them, it might be worth a shot, I'll sell them since I no longer have the car.

I also have a set of 6.9 rear axles for sale....

Fred Emmerich
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  #15  
Old 08-07-2011, 06:15 PM
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Originally Posted by gs sparhawk View Post


Otherwise, find that old 6.9 that is ready for the crusher because it is drooping and let ME buy it. I'm just an old fool with a few hundred to spare.

sparky
Im not certain why the one i saw in pick and pull was there, I mainly meant that if one needed a complete rebuild of the suspension system, a $2k 6.9 isn't likely to receive a $6-$7k suspension rebuild. I doubt I could ever afford one anyway, but if I could I would try to keep the proper suspension if possible.
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