I have the problem in the same area. But a little bit more serious.
One c280 came to me with complaint that central locking isnt working. Pump motor burned- so i replaced it with a different one (motor not the whole PSE). Everything was working fine ntil car left garage. The vacuum pump started working constantly when the throttle was apllied. Here is the interesting part - the more throttle- the faster pump runs. I checked the line from the pump up to vacuum valve block for leaks- none found. I unplugged all the lines from the vac valve block and tested them- everythig fine.
So i concluded that the problem is in vacuum valve block- got the new one- still no change. I plugged the vacuum line from the intake manifold- no problem. What components are there between the vacuum valve block and the pump vacuum line ?
Should there be a one way valve somewhere? As far as i understand the vacuum valve block should not let the vacuum pump to suck the air from manifold, but in this case it does.
Or is the problem in the PSE? It shuts down when there is sufficient vacuum in the line, so may it be going nuts?
Central lock is workig fine.
So, shortly speaking
there is a twoway connection between the PSE and the manifold.
Thanks for bearing with me, i am out of ideas and cant find any info on this MVA-SRU system.