Ok guys here is my question.

The locks on my new to me 85 300D have the following issues.

When I'm in the car and lock the driver door the driver rear door locks and so does the passenger front. The passenger side rear is dead. Yet when I get out of the car the key only locks the drivers door and the other 2 that are working will not lock with it. I assume I have a leak in the system because also the car does not shut off as smoothly as my previous diesel. It kinda shutters off. Where should I start guys? Thanks again.