This is just a little extra info-- and probably too late. I have a 79
300 TD, they have a vacuum pump on the front of the engine , and it has a pin that pushes the rubber diaphragm back and forth. I had oil getting into the lines to the air intake, etc. I bought a new (old stock) diaphragm from a private mechanic, and ignored the instructions about '" preload",, I just took out the old one and put in the new one, it took about 1 1/2 hours, and it works ok. lorenzo...