Vacuum leak for sure. Either the supply hoses are bad (check all the rubber connectors, they are usually dead by now and leaking) or the servos themselves are going. Won't move at all when shot.

Get a MitiVac hand pump, it will be invaluable in chasing down the leaks. I ought to see if I can the the manufacturer to pay me, I recommend them nearly every day on the forum!

Hook up the pump and see if the system as a whole holds vac (the green plastic line by the brake booster). If it does, then the leak is in the engine compartment or the line is plugged, or the vac pump is sick. If it leaks down, the leak(s) are in the climate control and you will have to chase them down.

Good point about the electrical contact, though -- both my W124's have wide temp variations and the 300D runs cold sometimes -- may need to do your repair to mine after I check the sensor hose.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!