So, new 3722 pump and Arnott’s best valve block installed. Malfunction no longer displayed. I left car at maximum height for two weeks with no sagging. Now that I’ve started driving it again and it has returned to normal ride height it seems to me that the air pump runs more frequently than it should.
What’s normal?

 

No one can answer what normal running time is.

Check the connections at the valve block. Perhaps the line to the reservoir is now leaking.

 

By the way, I never change the fittings when I service the system. Only change the fittings if they leak. I also spray the outside of the fitting with silicone before reconnecting, to protect and lubricate the o-rings.

 

for my 2007 GL450, the air pumps would run 4~8 seconds at the beginning of each trip.

 

You should not be able to hear the pump running when driving. But it runs whenever it needs to is the short answer.

if your pump is that noisy, investigate.

 

The OEM pump was not noisy.
The original pump and manifold was replaced in 2022 with a kit from FCP euro (arnott brand)
The new pump is louder, and can be heard when the GL is running (the GL engine is pretty quiet). Other users also reported louder arnott pump.

 

The pump will run much more than that - actually quite often as the car is being used. You just can't hear it.

Sculler... maybe we could compare "run time" in the diagnostics? It wouldn't be definitive since there are multiple variables, though.

 

Yes during the trip it's hard to hear the pump anymore.
heard that there is a air tank/reservoir in GL, it should reduce the number of times the pump kicks in.

 

The system is designed to use the reservoir to adjust ride height when your trip begins.

The pump is activated to refill the reservoir, but it waits until the engine is running in order to mask the noise.

If you hear the pump running every time you start up, the reservoir, or the hoses and connetions leading to it, are probably leaking.

 

not sure if there is a post regarding how to replace the air reservoir, hopefully its not very difficult.
on the other hand, replacing the pump and manifold is pretty easy if the front bumper cover is removed, basically plug and play.

 

Looks like a very easy job but I’ll bet the reservoir is a very spendy part.
I’ll have to check my airline connections at the pump outlet, the valve block and the reservoir with soapy water spray again.

 

The reservoir is readily accessible. It is underneath, just forward of the rear bumper.

I highly doubt the reservoir would spring a leak. Far more likely is the connections, particularly at the valve block, or the line itself, if it got damaged.

 

in my case, since each time the pump only run several seconds, and the GL does not lower itself after parking over night, Seems there is no need to worry about the air suspension system for now.

 

If you have a bidirectional tool, you could check the reservoir pressure for leakdown: at shutdown and after an idle period.

I doubt it is worth tearing apart the interior to check the lines to the back.

I don't notice my air pump running on any regular basis.

 

the whole propose of the pump is to fill than tank with16 bar of air pressure at all times. The tank then inflates each air spring - not the pump.

the pump should be almost silent, barely detectable at idle with an ear by the front right wheel. Doublecheck that you used all the rubber mounting pads and if so in the correct orientation.

 

yes there are rubber boot/bushings on the bolt that connect the pump to the aluminum bumper bar.
those rubber boots are really old.

 

I’m evidently a slow learner but I think I have reached a successful conclusion.
The malfunction was displayed because some former owner had installed a $50 Amazon valve block and my air pump was weak by being over worked.
New 3722 Arnott pump and a 3823 Arnott valve block installed and malfunction display has never returned.
icarsoft MB 2 was very useful once I realized I had to erase the old DCT codes in Airmatic. I now have no DCT codes.
Thanks to all for your help!