W111 280SE Coupe central locking - none of the doors lock anymore - vacuum pump or pillar reservoir

Hugo..

The W111 Coupe vacuum line from pump to reservoir runs along the inside of the right rear quarter panel, behind the trim card, then transitions through a grommet into the C-pillar.. the most common failure point is at that grommet - the rubber perishes and the line either pulls out or the connection cracks at the right-angle bend just past the grommet.

Pull the right rear quarter trim only. You will see the line. Inspect at the grommet first. 80% of cases it is there.

If the line is intact at the grommet, the second failure point is the rubber elbow inside the C-pillar where the line connects to the reservoir. That requires headliner drop. Less common but I have seen it twice.

Do not blame the reservoir itself before inspecting the line. The reservoir is a steel sphere and rarely fails.

Hugo. No drinks owed. Steve walked me through this one in 2011 on a 220SEb. The grommet failure is consistent across the Heckflosse, the W111 Coupe, and the early W108.

If you want to make it last, when you fit the new line, use a wrap of self-amalgamating rubber tape at the grommet entry. Not original but stops the next failure for another 30 years.