I'm having some vacuum trouble with my 84 300D, For a while I have ahd a leak and my car would not shut off on its own, well i was told how to just bypass that 4 way connector under the hood and I got it to shut off with the key. I got under the hood the other night and used some rtv sealer on the lines to fix the leak, Well it worked great! the car shut right off with the key and my door locks worked great. Then a short bit later when i tried to shut it off it took about 15 - 20 secs after i took the key out to die. I bought all new rubber lines and t connectors for under the hood and its still doing the same thing. Where else should I check for a leak?

Check the line going to the vacuum valve on the ignition switch and the line from the switch to the shut off with a mighty vac. If they test good. check the vacuum valve on the ignition switch with the mighty vac.

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Dave
1983 300D Daily Driver

Try locking the doors when it is having trouble shutting down or lock them BEFORE you shut it down and see if it makes a difference. Your vacuum shutdown pod on the injection pump might be going bad. If you suspect the locks, only disconnect the YELLOW vac line under the hood and plug the rubber connector. That isolates the locks only. See if it shuts down better. A Mightyvac vacuum pump is real handy for these old Mercedes to find the vac leaks at the doors and other vac operated things on the car. Get one at an auto parts store.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

Thank you guys for the info, Ill try it out tomorrow

The leak is coming from the lock system. I bypassed it and the car shuts off fine. I am going go through all of it and I will let you know what I find. Thanks again

You may know this or not but pull up the carpets and look for the vacuum junctions for each door under the plastic guard on the floor. You can then disconect each door by itself and check each vacuum element without pulling apart the door. Generally with the later door lock vac pulls, the boot goes bad where the rod comes out of the vac element. I believe it is on the side that is the "unlock". An external vacuum source is extreamly handy to trouble shoot this problem. I use my electric A/C vac pump and plumbed up a gauge and valve to evacuate the line, close the valve and watch the gauge. Be sure to check BOTH lines coming from each door except the drivers door. The drivers door doesn't have a vacuum element in it, only the vacuum switch valve.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.