need help with 300td hydraulic suspension - Page 2 - PeachParts Mercedes-Benz Forum

Maxbumpo · #16 10-22-2007, 07:26 AM

Bruckman's post continued:

TO BLEED:
- Engine off, rear of car over a pit or on ramps, open the bleed screw. The car will fall slightly.
- Without added load, opening the bleed screw does NOTHING to bleed the struts, so leave the bleed screw open, get out from under the car and add as much weight as possible to the car, especially the rear. Use patio stones, tools, kitty litter, children, friends, etc. The goal is to push the rear of the car down as far as possible to expel air from the struts and lines.
- -With the car loaded, and having CLEANED the reservoir and replaced the filter and filled the fluid to the MAX mark, have an assistant start the engine.
- -Watch the fluid emerging from the bleed screw. When you see a steady stream of clean fluid (blue, not black!), close the screw. Don't bleed for too long or you'll drain the reservoir.
- -With the screw closed, the car should rise to normal ride height.
This could take a couple of minutes unless the engine is run at a fast idle. You now have only a little bit of trapped air located at the top of each strut.
- -Open the bleed screw again slowly and carefully. Beware that the car will fall, pushing the air out of the struts and lines, back to the level controller/bleed screw. Once the car sags, close the bleed screw and allow the car to rise to normal height.
- -Leave the engine running while you unload everything/everyone from the car.

As a follow-up to my last message, BEFORE beginning any work on the self-leveling system, you should read 32-501.pdf in the Chassis section of the W123 manuals. Contact me if you don't have access to
32-501.

The self-leveling system is very simple and extremely reliable given its capabilities. The biggest problem with the self-leveling system is that most mechanics, dealers included, don't seem to understand it. They throw parts at it instead.

So many times I've read about struts being replaced when, unless they actually LEAK, there is basically NOTHING in a hydraulic strut that wears out! The damping action is achieved through the restriction of fluid movement, and hydraulic fluid moving through a steel orifice doesn't cause wear! In 32-501 in the diagram 1324-8161/1 showing the cutaway strut you can see the flow restrictor about halfway down the strut, attached to the top of the piston.

Once you see how it works you begin to appreciate the elegant simplicity of it, from the inherent variable-rate nature of nitrogen gas, to the redundant security of having both steel and hydraulic springing in case the leveling system fails.

D.

johninva · #17 10-22-2007, 08:37 AM

ok let me see if i have this straight ...

Quote:

If the original rod setting is lost, try this: with engine running, disconnect rod and move the lever to the neutral position

is the neutral position when the rear is all the way lowered ?

and if in this neutral position the clearance between wheel center and fender is less than the aforementioned correct height but the the rear will rise with manual control of the lever -> that this points to a bad bit in the valve that controls the idle leveling part of the valve ?

JimmyL · #18 10-22-2007, 09:50 AM

Interesting info from M. Dillon. I also duly noted his opinion that the wagon height is hydraulically dependent. It isn't the springs that give the wagon the correct height as has been discussed recently.
I am guessing the the link is supposed to be adjustable since it is in fact made with adjustable end pieces.

I think the misunderstanding is the arm off the valve assembly. The arm that the adjustable link attaches to. It grips the shaft coming out of the valve assembly, and it's position is specific. The link is supposed to be adjustable in order to achieve the correct static height. That is why they give the correct spec from center of wheel to arch.....

johninva · #19 10-22-2007, 10:27 AM

my understanding from maxbumpo's post is that even with the link unattached from the valve arm and with the valve arm at the neutral position the car should be maintaining the 13 or so inch static height and that having to adjust the link to raise the rear up to achieve the correct height is BAD and that it is an indication that the valve is not functioning correctly.

Is this the correct understanding ?

JimmyL · #20 10-22-2007, 10:59 AM

The valve is just flowing and restricting fluid. How would it be bad to be in a certain position??

johninva · #21 10-22-2007, 11:20 AM

Quote:

2. Both before and after replacing the spheres, the rear suspension sagged within a few minutes of shutdown, or even while running after highway driving on warm days. The problem was an internal leak in the self-leveling valve, which maintains a base pressure at all times even without cargo. If your car droops it is NOT the rear springs, it's the valve failing to hold the base pressure.

Quote:

Once everything is hooked up again, you should be able to start the car and watch it rise to normal operating height EVEN IF the actuating lever on the valve is set to release the pressure in the system. I left the actuating lever disconnected initially so that I could verify the function of the valve etc. The car should maintain a basic height/pressure with the lever in the neutral or "release" positions. Moving the lever to the "fill" position should result in an even higher ride (unless a corresponding weight has been added to the car).

i'd assumed the neutral position was when the valve ought to be maintaining this "base pressure" and giving you proper unloaded ride height.

Quote:

The valve is just flowing and restricting fluid. How would it be bad to be in a certain position??

i dont know - but isnt that what he seems to be saying - that if your waggon is saggin and your shocks aint leakin that your valve is busted - or else you would have proper ride height in the neutral or release positions of the lever ?

Maxbumpo · #22 10-22-2007, 01:42 PM

Quote:

Originally Posted by johninva

my understanding from maxbumpo's post is that even with the link unattached from the valve arm and with the valve arm at the neutral position the car should be maintaining the 13 or so inch static height and that having to adjust the link to raise the rear up to achieve the correct height is BAD and that it is an indication that the valve is not functioning correctly.

Is this the correct understanding ?

Yes.

Maxbumpo · #23 10-22-2007, 01:47 PM

Quote:

Originally Posted by JimmyL

The valve is just flowing and restricting fluid. How would it be bad to be in a certain position??

The control valve has three different valves inside.
1) Base pressure valve, which maintains base pressure to set correct ride height when vehicle is unloaded.
2) Adjusting valve to increase beyond base pressure when loaded (this is the one connected to the arm/rod/torsion bar).
3) Overpressure valve (safety relief).

If you leave it in the 'Fill' position and keep a higher-than-normal pressure in the system, the base pressure valve WILL fail, and when you park the car the rear end will sag. Eventually, it will sag all the time.

johninva · #24 10-23-2007, 08:01 AM

so until 2 days i could never see the tops of my tires on the rear, i impatiently adjusted the adjustable link to have the car raise up to get the 13.5" clearance from center of wheel cap to fender lip. Then I learned that this was BAD to have the valve in the fill position to maintain a static unloaded height. So i crawled under there, undid the connection from the link to the arm and lowered the arm to netural/release position, the car barely dropped at all, still can see tops of tires for sure, its like it is all of a sudden maintaining base pressure. could some internals on the valve have been gunked up or stuck ? also i noted that where the link is adjusted to now is where it ruffly should be according to the nail through the hole on the lever into the hole on the valve body method. also also now the ride seems a little bouncy, maybe a bad accumulator or two, is there anyway to do a quick test without removing from the vehicle, i tap on one it sounds hollow, i tap on the other it sounds not hollow ?
thanks for all your help

JimmyL · #25 10-23-2007, 10:06 AM

You would never want to replace just one accumulator. It is like replacing one shock. They're about a hunnert bucks apiece, and then you KNOW you are good there for a long time. They make a huge difference! With things working properly, there is no bounce AT ALL, and it absorbs bumps and dips beyond what you think it could do.....

nscarr · #26 10-28-2007, 10:46 PM

hi--

question on the new wagon--finally got around to looking at the sls and have the following situation:

1) rear end sag
2) no fluid in reservoir and one engine compartment fitting disconnected
3) gas shocks inside springs (picture 1)
4) nothing attached to accumulators (picture 3)
5) ride is okay, but speed bumps cause... bump

so i'm concluding that my sls was disconnected. would the hydraulic shocks normally sit within the springs?

in the picture 2 below, is this the normal setup for the shock?

i'm in the process of removing other parts of the system, and was wondering if some folks with experience could opine on what springs and shocks to use--was thinking of using **************.com's kit--any experience there?

thanks a bunch!
-noah

#27 10-28-2007, 10:50 PM

Somebody replaced yours with normal shocks. What about the pump on the engine, what did they do with it?

Avoid Mercedesource completely, they are crooks.

nscarr · #28 10-28-2007, 10:51 PM

so would you recommend the 126 springs with bilstein hds?

#29 10-28-2007, 10:59 PM

I'd suggest air shocks.

http://www.monroe.com/products/mp_detail.asp?cat=0&detail=Max%20Air

Maxbumpo · #30 10-29-2007, 07:51 AM

Quote:

Originally Posted by nscarr

so would you recommend the 126 springs with bilstein hds?

I'd suggest you restore the SLS to factory specs; nothing else will even come close to the ride comfort and utility. Basically, your car is crippled and dangerous to drive in that condition.