I heard somewhere that mercedes started using
a backup vacuum pump for the door lock
system on newer merecedes.
Is this true and is it possible to
put one in a 78 300D?
My system works well, just sometimes when it
is cool out it is slow or doesn't work
if the car sits for a long time.

Thanks!
Matthew

Repair your power door lock system will cost lest $ then putting new system,usually is the door element go out.

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MB STARS Master Guild Technician,12 years MB tech
6 years independent shop owner

The new systems don't have a back-up pump the just use a pump that works both directions.

Your system uses vacuum to lock and to unlock. The new systems have only one line and use vacuum one way and pressure the other way.

You could replace all your vacuum elements a couple times for what the pumps cost alone. Fix your system and I would recommend replacing all the door actuators unless you know there history. The labor to find a small leak will cost as much as the labor to replace all three door elements. If you only replace a single leaker the system works with higher vacuum and the rest are subject to this and fail sooner.


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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Be sure to have the system reservoir checked tooo..I have seen them leak/

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM