[W140Gill]

you have a vacuum leak.

It could be from any of the below

* Either one of the bags in the front seats
* The vacuum hose connecters under the front seats
* The vacuum connectors under the rear bench leading into the ZF pump
* or a defective ZF pump($$$$$)

My guess is that the pump in trying to maintain pressure inside the front lumbar bags. As its leaking away the pump detects pressure loss and refills the seats.
If there is a vacuum leak on any of the seats, both will malfunction. They are connected to the same line and operated by the same relay in the ZF pump. Check these lines 1st. The are easily distinguished by their grey colour .There are three lines in all. Two are vacuum - and draw vacuum, the other line is vacuum + and pumps air into the seats.

My ZF pump was recently replaced. the front lumbar support was the first device to fail.
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[W140Gill]

wise move.
Detailers, most mechanics included, dont give a sh!t about your car and rush t...

wise move.
Detailers, most mechanics included, dont give a sh!t about your car and rush to finish the job. I like to watch or check up on them whenever my car is being worked on.
Cleaning is only ever done my me.
My car has just gone onto the shop for a transmission overhaul and front engine gasket replacement (M104). No doubt, I'll be stopping in to check the progress
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