Suspension levelling valve

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W108-1967 250S
500 K
Posts: 516
Joined: Mon 11 Oct, 2010 9:28 pm
Model you own: w210
Location: Tamworth NSW

Suspension levelling valve

Post by W108-1967 250S » Thu 09 Jun, 2016 9:54 am

My W210 E240 Wagon has given me the last 5 years trouble free luxurious motoring, bought second hand she is now 16 years old so not a bad record. :occasion4: After a good wash she looks very good, like a quality car should!

However, a problem which has come up before, some years back in the service record, is a small leak coming from the suspension levelling valve attached to the middle of the rear torsion bar. I had a road worthy rego renewal check done recently and the testing officer reported there was a minor fluid leak from the "rear brake restricting valve".

Anything with brakes causes me to toss and turn at night.... A quick look up her rear with my trolley jack and trestles, confirmed it was the suspension levelling valve. My understanding is depending on weight loaded in the rear, this valve will send fluid to the rear shocks which have these nitrogen filled spherical bottles on them, levelling the suspension. The sensing valve is a small unit attached to a pretty flimsy bracket, with a sensing arm that is attached to the rear torsion bar....so trying to tighten pipe fittings will not be easy (mounting bracket quickly starts to distort) without supporting it? I see it has a bleed nipple on it, I assume to bleed the system if the valve is replaced? I think the only fix is valve replacement? :pale: How do you bleed this system? Is it a DIY? Any advice/inputs appreciated. The leak is pretty minor but it drips onto the diff and is making the diff and drive shafts "oily" over time!

W108-1967 250S
500 K
Posts: 516
Joined: Mon 11 Oct, 2010 9:28 pm
Model you own: w210
Location: Tamworth NSW

Re: Suspension levelling valve

Post by W108-1967 250S » Sat 05 Aug, 2017 9:16 pm

Well the saga of the "sagging rear" has concluded! Will try keep it short. Was not so much the rear levelling system which is fairly simple as such, but was more getting the run around by stealerships!! :argue:
Firstly, after roadworthy inspectors accusing my car of having a leaking rear brake fluid pressure reducing valve leak, I managed to convince them it was the rear suspension levelling valve that was leaking. Should have ordered one from the sponsor I know....sorry!! Anyhow got a franchise dealer specialising in European cars to carry out an A service which had come up and as such asked them to replace the valve. This they did, but after getting it back the rear suspension was riding very hard indeed. So after some research I found out:
The levelling system runs off the power steering system using the power steering pump and the same fancy fluid, which is $$$$$$$$! Incidentally, the fluid reservoir has a little paper cartridge filter incorporated into the return line...mine was filthy, clearly hadn't been replaced in ages....I have now put in a new filter. The rear "shocks" are not shocks they are hydraulic jacks. If you drive with hard suspension you will damage their seals...$$$$$$$$$$$$$$$
The actual shocks are in fact pressure spheres in the system lines, charged with high pressure nitrogen. The nitrogen is compressed by the fluid in the spheres which have a rubber membrane separating fluid and nitrogen. This provides the shock absorption. When these fail through age, the spheres completely fill with fluid and the suspension rides hard as hell!
So decided I would replace the nitro spheres myself. Got under car (not something I like doing....with axle stands, wish I had a hoist, life would be simple... :wall: ) and saw that the link attaching the new valve to the rear suspension torsion bar which adjusts the height as the torsion bar position moves when you load lots of beer in the back....had been broken and rather crudely re-attached with cable ties... :angry4:
Sooo, after ordering new nitro spheres through stealership (tricky as considered dangerous goods due pressurised spheres so can't air freight say the Yank spares websites?) the spheres shipping from Singapore, I decide to get stealership to sort out the spheres and while they are under the car, fix the link.
This is where it gets interesting...they sort spheres, rear end has its old famous E class magic carpet ride back.....but...they tell me to fix the link, I have to buy a new valve, as "its all one unit" :drunken: ..$$$$$$$$$$$$$!! Strange think I, as I'm sure my pics show a part number on it. But now go back to crowd who worked their artistry with cable ties and tell them Mercedes Benz does not use cable ties in their suspension design and that I'm not happy...They agree to fix the link and surprise,
20170730_153004.jpg
surprise, have no problem ordering a new link, also from Singapore....Stealerships....very good nickname!!! :angry5:
Still not finalised as after they "fix" the link, I take family on outing. After getting home I see the rear is riding very high...?? Must be the link which needs adjusting....so back onto the axle stands she goes and under her rump I go....only to see the locating pin and bolt which attach the triangular shaped plate on the link to the valve, has lost the bolt and as a result the link has dropped right of the adjusting valve arm, which now uncontrolled, had started pumpimg the back up higher and higher....Boy oh boy! So after re-attaching it with a nice new shiny nyloc nut from my stock in the garage, I adjust the link slightly, check everything is tight and take her for a test drive....get back and see the rear wheels are sitting perfectly in the wheel arches and finally the saga of the sagging rear appears over.....if you want it done properly......do it yourself!!
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