machild

CLS 55 with 67K miles. Car had not been started in a couple of weeks and when I did start it, I received car too low message and to wait briefly while it rises. I heard the air suspension compressor come as I woke up the car, but the car never did rise.

I hooked up Star and found a couple fault codes and one for the air system for high ambient temps (we had near 100*F here recently, but that doesn’t seem all that hot). I cleared codes and after starting the car again ran another Star scan to see if new fault codes were set. No codes.

I went through the Airmatic module and attempted to raise or lower the car corner by corner with no success. The air reservoir was reported to be at 7.14bar and the rear height was listed as -26 while the front was reported at -92.

I’ve done a search here on the issue but have not found my situation. Not sure where to start on chasing down the issue – air distribution valve?

nd-photo.nl

The distribution block would also be my first best guess...Could also be the compressor purge valve which is stuck open? If its the original compressor, that might also be something to look into.

To be honest, seems I also have an air leak again, focussed on the rear left...

machild

Thanks, Andy. I'm pretty sure it is the original compressor. Based on what I have seen so far, with 67K miles it would be a bit early to typically expect a bad comperssor. Not that it can't be, just not typical. Is the purge valve part of the compessor or stand alone?

nd-photo.nl

Its part of the compressor, but you can service/replace them separately

machild

Thank you for this. Is there a way to test whether the purge valve is defective? And what/why is the purge valve purging?

A brief update - I started the car to see if it would rise. It did and I measured ~26 inches (660mm) from the floor to the highest point of the fender wheel opening. This was both front and back wheel openings. The rise switch on the shifter console is set for the rised position. I don't have a reference point as to the typical measurment for a fully stock (including wheels) CLS 55. The message on the dash continues to state 'wait breifly while the car is rising'. Of course, the message never went away.

After that measurement, I began to lift the car with a two post lift. The car had been lifted maybe 3-4 inches when there was a loud and significant whoosh of air from the front of the car. I assume that was some type of exhausting of the compressed air from the system. That did not occur when the car has been lifted in the past so I'm thinking it may have been from a leak source?

nd-photo.nl

If I am driving the car, I hear a whooshing noise every now and then from the front of the car, which is the purge valve working (purging excess pressure). It should also do this when you close the car, as it will then self level before it will sleep.

Coincidentally, I measured the fender gap in the rear as I am chasing my leak as well. It was 680mm (stock 19 inch AMG wheel, 285/30/19 tyre), but I believe it should sit even a little bit higher.

machild

I typically have heard my compressor run for a few secounds when I wake the car but never I never heard whoosh on lowering or otherwise. I typically drive in the lower setting and only raise the car when going into a steep drive opening or such. When I do rasie and lower it there is no whoosh. But, I guess the whoosh is part of the system. Thanks for the height check, 20mm difference in ride height is notable.

Are you using soapy water when looking for leaks?

Rune

I recently had to play with this too, and I always found it useful to do the compressor test first via star, just to rule that out.

The purge valve can also be actuated via star, which was quite useful when trying to diagnose things. In my case I had corroded/broken wires leading to the purge vale, which led to intermittent contact. Fixed this sourcing a new connector with pigtail, and soldering it on.

Another recent issue was that the connector for the pump power had developed an intermittent loose connection. This time a little tightening of the pins and some dielectric grease seems to have sorted it out.. for now (grin).

Good luck,
Rune

machild

@Rune This is helpful. I didn't see a test for the compressor or the purge valve in Star. I'll revisit it.

nd-photo.nl

No me neither (Autel), I only noticed the compressor test

machild

Ha - maybe we need some screen shots @Rune

Rune

hehe.. would not be the first time my mind inserted plausible but false information .
I know the compressor test menu is there, and will look for the purge valve tonight, and take a few screenshots.

Stay tuned,
Rune

machild

Anything you can come up with is most appreciated!