Greetings Gentlemen! Here's the deal: On my '85 300D Turbo, the central door lock system will normally work when the engine is running but less than 30 minutes after the engine was shut off, the door lock actuator/diaphragms will not respond/react anymore on the driver's/main lock knob.

1. All 4 doors, including fuel door and trunk lid diaphragms holds vacuum and responds through a MityVac on both lock and unlock hoses.
2. The black vacuum reservoir in the trunk holds vacuum.
3. Transmission shifts normal and smooth.
4. ACC vent diaphragms works and functions as it should.

Now the question is, if anyone of you have had the same symptoms:
1. What could be the culprit?
2. Why is the central lock working when engine is running/idling and not when the engine is turned off.

Any help will be greatly appreciated! Thanks in advance and have a happy holidays!

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'85 300D Turbo - CA Version

2. you have a leak somewhere

1. How about the check valves? Did you check the one in the engine compartment leading to the interior and namely the central locking??

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1982 300TD 210K miles ("The Replacement" aka "The Anvil") - SOLD
1979 300SD 245K miles (never ending project)
2007 Pinarello F3:13
1995 Ducati 916 (SOLD, sniff)
1999 Ducati 900SSie (SOLD)

Sounds like your pump my not be pulling enough vac. Connect your mity vac to one of the ports on the main vac line from the vac pump to the break booster. Plug the other one if you have two. Then start the car. And read the mity vac. If you have over 20" the pump and booster are working properly. If not one is leaking. Next remove the main vac line from the break booster and then plug the end (I usually lick my thumb and put it over the end). Again with the car running read the mity vac. If your reading jumps up to above 20" then the booster is leaking, if there is no change, and it's still low then the pump is at fault. It could be a bad check valve on the pump or the pump may need to be rebuilt.

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Did you verify if your vacuum connectors are good? I ended up replacing all of them in my wagon (they are common culprits for slow leaks). After I did, the hatch actuator needed to be repaired and I have no more leaks. I replaced all the connectors under the hood too, and the whole system works better now.

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Chad
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys

1984 300d Turbo 145k
Door Locks, Fuel And Trunk Lock All The Same Line, My Fuel Door Vacuum Actuator Leaked, Replace All Actuators And Check The 3 Port Check Valve In Left Side Engine Above The Oil Filter And Vacuum Diagrams This Site Do A Search

Thanks for all the help and insights!
Here's what I did:
1. Under the front passenger floor mat, I plugged/capped each line that goes to each door one at a time and run the engine until it starts to hold vacuum and operate the automatic feature but didn't find any one of them diaphragm that is leaking, but still would not hold vacuum when the engine is OFF.
2. Swapped the yellow check valve with a known good check valve, but still, the same, loses vacuum when engine is OFF.
3. Vacuum suction is between 20-22mmHg on both nipple whether the main vacuum hose is connected or not to the brake booster.

Now what????

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'85 300D Turbo - CA Version

If you have a minivac, individually pull a vacuum on each section of the system and see which one(s) leak down more quickly. You have a small leak someplace, just a matter of tracking it down.