Just dealt with something similar over the weekend. In our case, we had the star diagnosis and ran pneumatic tests.

Summarily, it was the valve block leaking. Also dependson how much. Test with spray bottle of appropriate liquid.

Example in video

No kit to fix and part not replaced yet, but in the meantime we sealed up with glue,its holding.

In the image you can see the air leaking so much as we spray with detergent.

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Also its the same car, 2004 s500. Corrossion I believe was the reason it failed so badly. If you can have a scan and all 4 struts drop, its almost certain you should change the valve block and 'pump' up.

Note that you may not hear the leaking, especially when the pump is in action, also the leak may be so slight that you may hardly hear it.

The star system will accurately point you to the problem. In the absence of that, fix /replace valve block

All the best

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Thanks for the excellent information. Soap tested valve block,pump, and storage tank with no leaks on any of these. Going to look into the rear struts tomorrow but still losing the game so far but it isn't over yet. Thanks Noetico!

 

O great, do keep us posted.

All the best

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Hi,

Remember, Valve Blocks can leak off internally as well as externally, but SDS will be required to prove that

HTH,

Cheers Dave

 

SDS can occasionally point to a air valve as being defective, when in fact it is a leaking shock. I had a driver front shock leaking, you could hear the air escaping. Running SDS, it showed a leak at all four shocks, thus pointing to a air block failure. Attached are pics showing SDS pointing to air valve, and after front left shock replacement, then showing all was well with the air block.

Just to recap, the four attached pictures show a failure on all four shicks, yet the only failure was the front left shock, the following set of pics then shows all shocks diagnosing good after the front left shock replacment.

 

Let me ask, regarding the attached images; the test ended with the black bar inside the red area for each test?

Did you test the compressor function? Compressor to valve block. Just curious

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Hi Mike,

Those pics are showing Strut Level Data but SDS will also measure Air Leakage

I'm no expert, as I haven't played with this in a long while, but @cowboyt got very involved with it recently, as did someone else here, EDIT, @noetico and they found SDS will do specific Pressure and Leak Off tests which do indicate where the Fault lies, will indicate which Valve is leaking internally, and apparently it even has a very long timed test for small leaks :dunno:

HTH,

Cheers Dave

 

Precisely, SDS will test each strut for leaks, ie strut to VB, and this is crucial; i can confidently say the control unit actuates the VB to lock each strut at the correct height using the valves within it. So each strut can be tested while the others are locked/closed.

The test pumps each strut and corrects it as needed.

You can even raise each strut manually using f keys, lower, raise... Etc. So you can use this to isolate the vb in a malfunctioning system, I assume the vb has no leaks in this case.

I may have said this before; Once we had a a gl450 to assist with, the VB was having issues, we tested each strut, raised them manually to within recommended height and unplugged the VB, until the owner can replace. Its been almost 3 months now. Whenever we left the vb plugged, the struts collapsed after some hours.

I think from the tests, it is obvious the pressure is maintained in line between the strut and the valve for each strut. In the gl450 above, the problem appeared to be 1 or 2 valves not closing in a timely manner and we had for example, front right rise too high and burst twice.





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This one's quite lengthy, sorry.

One thing I also like to do is use the initial startup function to refresh control modules when necessary.

So when you can, clear any codes and initialize the control module. Then operate it.

Also let me mention that, in testing the leaks, its not sufficient to spray just the tube ends, spray the VB body, underneath where the 2 mounts are and on top, summarily all around the where plastic housing, paying attention to where the plastic housing meets the aluminium case.

There is a long test, for struts as well, basically you just park the car for over 12 hours and see which struts fall, assuming you have done the system tests for leaks between strut and vb and vb to compressor and all passed.

Its logical, if the pressure test that require pumping from the compressor all pass and the valves lock in, the struts should stay pressured, if they fall then your dealing with 1 or more strut leaks.

If in the test, you dont come to the required height in the green area in sds, then you may have a weak pump that simply doesn't get to the required height, and das should tell you.

Now, its all human designed, so the long test is just in case there is a very minute leak in the vb or strut that will be so infinitesimal when the pump is operational or even in a short while, but overtime will considerably drop the pressure.

Im thinking of a paste, like toothpaste, you can put on all connections:

1. Air tube coupling on top of strut
2. Air tube coupling at vb, all
3. Air tube coupling at compressor
4. Air tube coupling at Tank
5. Vb body

Now if you put the paste and keep it parked, hoping the paste doesnt dry out, you may find bubbles in the paste. Should be best with light colored, semi transparent toothpaste.

Pheww... Long post, sorry.

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Hi,

Thanks for responding, it was you I was thinking of above, some very good info in those last 3 posts :wink

Cheers Dave

 

Lol. Thanks Sir. Great inputs from you as well.

Cheers

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:big laugh:

:dunno: about the "Sir" LOL, more like :asshat:

 

OK guys, soI unplugged the VB and now it holds air. So is it the VB or the control module. I'm gonna go with the VB. I'll post when I know more. Thanks for all the replies and info you all provided. Greg

 

Cool, this exact thing happened with a gl450 i talked about earlier in this thread. So you have identified the problem, easy...

 

Definitely the VB. It's not functioning well. What you have is a neat fix while you get a good one, you read my earlier post right, same on a gl450,3 months+ still ok until owner decides to buy the part.

Won't be bad to also reset the control module, try everything agajn conclusively. Thats if you haven't done already