Have you closly looked at the airline itself?

I would replace the lines just as a matter of maintenance if I was having the issues you are. Can't remember if I read of these lines cracking specifically but all plastic airlines deteriorate.

 

What can happen which causes one air spring to drop is that there is an external "mechanical" leak somewhere in the "middle" of the air system - that is near the compressor, or in the compressor air dryer cap or the big air tank; that sort of thing that lets air out slowly overnight even if the system is depowered.

In your case, envision where the front block valves all three orifices, or at least the centre orifice are sealing well and essentially no air escapes from the front two air springs.

Now consider that if the orifice in the rear block valve that feeds the left rear air spring leaks and also that centre orifice, then air from the left rear air spring could flow thru the rear block valve to the "middle" area and then escape out say a leak in the air tank.

You would not be looking for a slow external leak in the "middle" parts, but that is where it could be. Being a slow leak, during the day, the air compressor has no problem keeping up.

 

All of the lines "look" ok, I have sprayed them all down everywhere, all connections, all valve blocks, reservoir, pump, no visible leaks.



I guess I am considering replacing the rear valve block...can I swap the front one to the back for testing purposes?

 

The leak is not that slow, it is visibly dropping in a matter of 30 minutes...not to the bump stop but about an inch.

 

So I swapped the valve blocks and now the right front is leaking down. Valve block it is. What is the actual difference between the front and rear? It isn't behaving any different, still needs software update.

 

First off, I am surprised the swap worked. I thought there would be a connector shape issue.

Does that mean you also put the front block valve in the rear and all was good at the back?

Other than physical, I do not know if there are differences between front and rear, but I think if I recall correctly, the orifices sizes are different - pretty certain I am correct re orifice size.

In other words, if the rear is bad, you need a new rear block valve and the front unit belongs in the front.

All this is good news however.

 

actually everything fit just perfect, fittings, connector plug...everything, as if they are completely the same.

Ao agter the swap: rear did not lose height, front right did lose height.

 

That is real good news - that the swap for test purposes worked well. That is the first time I have heard of anyone doing that so well done.

I am pretty certain I am correct about the orifice sizes being different. The idea is to match the rate of fall of both the front and rear.

The older FFRR did the camel thing, front down, then rear, or vice versa, but with the 3, the idea was to have front and rear drop or rise at the same rate.

The block valve orifices are the timing device re deflation and I suppose inflation, so due to differing air volumes of the front vs the rear air springs, the orifices sizes were made to differ.

 

Oh yeah, that makes sense. I thought you meant the hose connections. Internally they are differewnt yes.

 

The majority of the air lines are nominal 6mm, and a few 10 mm.

Re fitting size, 6mm is close to 1/4" but that is the problem, close.

One can buy the 6mm fittings at Mercedes, Audie etc as all the EU guys use metric; also Toyota etc.

I think also Ford and GM now use 6mm fittings on their new production high end air suspension vehicles also.

Most US domestic highway tractors such as Kenworth use 1/4" or larger SAE air lines.