Just bought the car 2006 ML500, car was not starting and all 4 suspension where down bottomed out. Fix the no start and now left with suspension problem. The scanner code I got is 5508 and 5400 cleared the code tried to raise the car the compressor does not engage. I checked the fuse in the trunk and 40 amp fuse and relay front passenger side. The relay has been changed to hella by p.o. checked The relay resistance as well it is good, changed 40 amp even took compressor out and bench tested with 12v the air is very strong could not block since I dont have the pressure tester. Checked the connector to the compressor and it is getting 14v while car is on. Question is why is the compressor not engaging? After I cleared the code 5508 returned and visit workshop. I hear hissing sound around the power steering reservoir while car is running. I do not know if that is normal. Is the air reservoir tank front driver side where I hear the hissing?

 

The reservoirs are located in the rear.

The leak you are hearing is probably coming from the left side strut.

 

Thank you for fast response and diagram.
All the airbags dont have air in them. I jumped the compressor with 12v after I installed it back in the car with car running raised button pushed no air went to the struts. I do not know how long it take to fill reservoir before the air suspension rises....

 

You must have a scanner to read the codes in the Airmatic Cont. Module. Look at all the possibilities.

 

I did mention the codes. First time I scanned it 5508 and 5400 was the code. After resting I keep getting 5508 pressure leak.....

 

Sorry for the miss on the codes, getting too old.

Soapy water in a spray bottle and spray around the top of the left front strut where the pressure line is,

 

No worries long story so easy to miss.
I tried it before with no luck but I didnt wait 15-30 mins which I will do it again. One problem though the struts have zero air in them, how can I manually fill the struts to check for leaks. P.o said two front struts where changed but it's safe to assume they are not changed.

 

look at the volt on left rear level sensor, it looks very low on comparison to the others. Passenger side front I have lifted up little with jack that's why the reading is positive.

 

Thank you everyone that helped!! Fixed the problem when I changed the Airomatic air compressor.