Vacuum Lines
 

I am fixing the central locking system on my 77 300D and I need access to the left kick panel or rather behind it. I think the plastic line is broken where it passes through the hinge area. I did not see any screws right off, but I am going to need to get in behind that panel! I think.

Those vacuum controlled central locking systems can be a pain. You would be wise to go through ALL of the vacuum lines and actuators in the central locking system with a vacuum test gun while making this repair. Usually you will find one problem, fix it, put it back together, only to find that there is another leak further down somewhere.

Make sure to check the vacuum resevoir on those because they will be a common problem. They will hold vacuum for a while and slowly leak over the course of a couple days. I spent two full days diagnosing one of those cars at the dealership about 3 months ago. They can either be really easy or a total pain in the a#$.