Ryan:

Start in the engine compartment -- the vacuum systems for shutoff and A/C and locks are separate. If both are working funny, I'd suspect either a leaking line (where they both attach or at the booster) or a dead vaccuum pump.

If the diaphram in the vacuum pump is gone, you will be burning oil big time, as in a huge blue cloud out the back and a droning noise from the engine. The check valves can go bad, too.

On the big hose going to the brake booster there will be one or two (or three?) hard plastic lines attached. One should be brown with a blue stripe -- this goes to the ignition switch. The other will be green or blue (or both, I'm not too familiar with this model). One will run the locks, the other the A/C, usually. Check the rubber sleeves at the ends of the lines -- the hard plastic should be OK. The rubber goes bad, and the lines leak. You don't use all that much vacuum for the brakes.

The plastic T in the line can go bad, too.

Further up toward the passenger compartment there will be a couple blue plastic check valves in the line -- these can crack, and leak.

There are also several vacuum reserviors that look like a bunch of plastic balls stuck together, but I'm pretty sure they aren't your problem.

The vacuum lines are pretty easy to identify once you find them -- check all the connections and I'm sure you will find the problem is a rubber connector. They can be replaced with vacuum line of the appropriate size from the autoparts store.

To check the vacuum pump, pull a line off and check that there is strong vacuum in the main line. If you can't find any leaks and there is little or no vaccum in the line, the pump is bad.

You can check for leaks by sucking on a hose, but a mitivac or equivalent hand vacuum pump is MUCH easier -- some of the vacuum reservoirs are pretty large!

Peter

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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!