PeachParts Mercedes-Benz Forum - View Single Post - need help with 300td hydraulic suspension

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.