I have a well-maintained E550 with airmatic. All of the struts and springs have been changed with Arnott items about six years ago and last year I replaced the compressor assy as a preventative item.

A few days ago, I noticed that the vehicle was riding high. Not high enough to give me a warning, but visually high. Checking the system, I verified wiring integrity with my scan tool and when I lightly tapped on the vent solenoid at the compressor, the system started to lower the vehicle.

I've read a few articles about this valve sticking. Does anyone recommend that it be pulled and cleaned with spray silicone or something, or just replace the vent solenoid?

 

Even though I had no replies, I wanted to advise everyone of my final diagnosis and repair. It seems that the battery in the vehicle (from the dealer) was 3 1/2 years old. At rest, it only measured 11.3 volts and although it would start the car, there wasn't enough depth to the battery to properly run all of those systems. So, it would lift the vehicle, but the system would not release at the vent valve.

Now that it has a new battery, the voltage is on par and no more issues.

 

I wanted to add another update to this issue if anyone else has a similar issue.

The computer system formerly had low voltage codes and a new battery seemed to fix the issue. But, early in November, the problem returned. I also noted that now the system had high voltage codes in the systems. Driving the vehicle I noticed the occasional voltage spike to 15-16 volts and then returned to normal voltage. Also, the same time the struts were clicking up a storm trying to lower the car to no avail. I wondered if I had an alternator issue but the alternator was changed last year and is a Bosch reman unit.

I decided to test the vent valve on the compressor. When I removed it, there was pressure built up in the system which told me that residual pressure had been trapped at the vent valve. I removed the vent valve, plugged it in and commanded the vehicle to lower. Sure enough, a rush of air and the vehicle settled to ride height! There's my diagnosis, a bad vent valve.

I replaced the vent valve and all is well. There are no more high voltage codes and the voltage has not gone over 14.4 volts during a 30-minute monitoring session. It appears that if the vehicle cannot level itself, the computer strategy is to momentarily up the voltage to see if that will do anything. That's my theory on the high voltage codes that have not returned.

The vent valve was a $19 part. This is continued proof that diagnosing the problem will save dollars.