Thank you all again for making this forum such a life saver.
Recently replaced the water pump and she runs cool and even again thanks to the knowledge shared here.

However...
I've noticed lately that my automatic transmission (79 300D) is shifting strangely, shifting later than usual and slipping(?) a bit in the final downshift when braking . The fluid level is OK so I began worrying that it was something major. After reading through several searched threads here and a couple of off site links I believe it to be a vacuum problem (the door locks have gotten very sluggish, too).

I am almost totally unfamiliar with the vacuum system (aside from basic knowledge of phsycis). I plan on keeping this car for as many miles as possible, so I've purchased a metal Mityvac kit (upon advice from the forum). I'm just not sure where to begin checking. Do I start at the vacuum pump and work back to the problem areas or start at the problem and work back to the pump? Any other things I should be looking at here?

__________________
'79 300D "Jaeger"
'61 VW Baja "Frosch"
'92 Honda Shadow 600
'80 Honda 185 (cafe project)

Answer taken from the below web address.

http://www.mercedesdismantlers.com/diesel_vacuum_system#Diesel%20Vacuum%20System%20Troubleshooting

The Mercedes Benz diesel uses a bleed off system to regulate the amount of vacuum supplied to the transmission's vacuum modulator. This variable vacuum system regulates the 722.118 series transmission shift. If the vacuum system is incorrect, the transmission could shift through the gears immediately or have late shifts.

The variable vacuum system for the 722.3-- and 722.416 series transmission regulates how hard or soft the transmission shifts.

The supply is taken from the Power Brake Booster vacuum line ("T" in line). With the engine running, and the transmission full of oil, unplug the supply and install a vacuum gauge. The gauge's needle should jump up to 15" - 20" of vacuum. If the needle rises slowly, your supply is restricted. Remove the gauge and drill the orafice with a 1/16" drill bit. Make sure you do not drill all the way through the supply tube.

Now that the supply is good, you need to re-connect the vacuum line to the Booster Supply Line. Now disconnect the vacuum modulator line from the White Bleed Valve. Plug in the Vacuum gauge in the modulator line's place and take a vacuum reading. It should read 10" - 20" of vacuum. If not, check the white vacuum switches located on the top of the valve cover, blocking each one off to test for a vacuum leak. Check all the vacuum hose connections for leaks and check the EGR valve for leaks, as well. If any are leaking, replace them. Make sure that the linkage arm from the White Bleed Valve to the Injection pump is hooked in properly. If you are getting a good vacuum supply to the White Bleed Valve, but no vacuum to the modulator line, replace the bleed valve. If you are getting good supply to the bleed valve and you are getting 10"-20" of vacuum to the modulator, open and close the throttle slowly, with the engine running, and watch the vacuum gauge. It should drop according to throttle position. I.E.: Half throttle, half vacuum. Full throttle, no vacuum. If you don't get the proper regulation, you must replace the White Bleed Valve. When you finally get good vacuum regulation to the modulator, you are done.

kenn - thanks for the detailed explanation on troubleshooting the vacuum modulated auto tranny...
however...
I made the most basic mistake of becoming overzealous and posting before I had all the facts straight. As it turns out, the research I had done about the tranny problem does NOT pertain to my particular model. I actually have a physical ball and joint arm attached the throttle linkage to regulate shifting.

thanks again, will try not to waste your time in the future...

__________________
'79 300D "Jaeger"
'61 VW Baja "Frosch"
'92 Honda Shadow 600
'80 Honda 185 (cafe project)