Australian 6.9 low in rear but OK in front; also goes to High position at front

[6.9original]

Hi All -

I've been away for 3 weeks and came back to a very low rear end on the 6.9 (left and right).

When idling, it maintains normal height in the front (even left and right) and also responds to the raised H position at the front only.

There's no leak from back struts so I wonder if the back valve has stopped working while unused for that 3 week period? Or is it another easy fix?

Any help on the initial approach to the problem would be appreciated before I insert blocks and tow to workshop.

Thanks and regards.

[TJ 450]

It might be the rear valve but could also be the front even though it appears ok. Most likely scenario is one of the valves bypassing internally and you can see this by watching the fluid return in the tank, there will be a high volume returning if there is a malfunction.

Tim

[daantjie]

Start by cleaning your tank out and clean the little filter in the pressure regulator.  To find this one if you do not know already, you need to unbolt the "throttle screw" from the pressure regulator (from memory this is a 12mm bolt) facing the fire wall (bulk head) in situ.  Once removed you will need to suck this little filter out as it sits deep into this channel and the residual fluid tends to want to keep it sucked into it's port.  Be extremely careful not to lose this little filter as they are no longer available.  Clean out the pressure regulator while you're at it as well with some compressed air and carb cleaner once you have it on the bench (you will need to pull it anyway to replace the filter).  Use good flare wrenches as the hydro lines can be very tightly bolted onto the valve.
Then drop a new filter in the tank (under the pressure regulator),as well as fluid flush. Always start simple. Then I would move to the leveling valves. Probably a tiny piece of debris causing non seating of a check valve.

[6.9original]

Thanks, Tim and Daniel.
I will first clean the filters and check pressure and condition of fluid generally.
The rotating disk controlled by the dash knob (wire now disconnected) that selects Normal-Locked-High turns without resistance which is not right (it used to).
Cheers,
David.

[TJ 450]

Okay, another thing to check after cleaning everything out (before removing valves), is to prime the main high pressure feed as there may be an airlock.

To do this you need to remove the hose from the main pressure regulator and redirect into the tank, then start the car and run until a high volume of fluid is flowing. Once done, kill the ignition and refit hose. If the disc still flops around then, continue troubleshooting as before.

Tim

[6.9original]

Hi All, as part of the suspension overhaul, we're sourcing 5 x new nitrogen accumulator spheres. Car will be in Sydney. Australian members with a recent good lead on affordable spheres, where did you get them and how much please? Availability in Australia is essential. Lemfoerder, Febi-Bilstein or Corteco. I'm aware front are different to rear, etc. Thanks! 6.9 number #4811.

[6.9original]

The cells are classed as dangerous good so air transport is problematic. Any ideas on local supplier that's reasonably priced and suitable for 6.9s, Australian members?

[TJ 450]

I would have suggested MB Spares, but they are no longer an option. If being shipped from overseas, it would have to go via sea.

I wonder how much the dealers charge these days?

Tim

[6.9original]

AUD780 each from MB main dealer.

[6.9original]

$550 from independent. 7 years ago I paid $$335.