Last night the wife started her 2012 ML350 (Bluetec) in the driveway and I immediately heard a sharp knocking sound over and above the normal diesel noise. I immediately popped the hood and isolated it down to the vacuum pump. Putting my hand on the pump I could feel it rapping internally in time with the knocking sound. After about 3 minutes of idling, the knocking/rapping became intermittent, and at the 5 minute mark went away entirely.

Since it is the wife's daily driver I am not going to mess around and plan on ordering a new pump straight away. Anyone ever had to change one out or able to offer any tips? Lastly I know a dying vacuum pump can potentially destroy one of the older diesel engines (OM617, OM602, etc) Is it the same danger with the OM642? I ask as she may need to drive it for a few days until the new pump arrives.

Thanks

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)

Just remove the 4 bolts , line up the shaft reinstall 1/2 hour job