So I have been slowly going through my vacuum system to test for leaks, diagnose problems, and generally try and relieve frustration with my 83 300D.

Today I was testing with the Mighty Vac and applied too much force to what I guess is termed an 'orifice' [bad word choice IMHO but nobody's asking]. As you can see, I plugged it with a screw; I don't think I screwed it in far enough to enlarge the back of the hole where it connects with the main vac supply that continues on to the booster.

Image:


I decided to drive the vehicle carefully to test this out. I knew that the ignition vacuum was still intact and that the brakes worked, although I figured I'd have to manually shift the transmission.

I did disconnect the vac line that feeds the transmission while the car was not running. It did not hold vacuum. I am preparing to drive the car with MightyVac attached and see if it makes a difference. Could this be a failed 'modulator' [don't know if I am using the correct terminology yet]. Sorry for the poor image quality; hopefully you can see the crack in the 'connector':




To my surprise, not only were the brakes much stiffer than usual [in a good way, more responsive] but the car shifted as it usually does: ok into 1 and 2, then into 3 briefly and all the way to 4, bogging down the acceleration until I get up to speed.

So, my question is can I drive it like this until I replace the broken part? I am replacing the vacuum pump next week and can do the work then.

I don't mind having to put some 'effort' into driving the car for now until I fix it. I gotta get to work somehow. Do I need to arrange another ride lol?!

Thank you in advance.

PS: I shrank the images about 5 times but they keep showing up here as full sized. I use photobucket. Any recommendations for other platforms? Thanks.

yeah replace that cap with the crack in it! the entire modulator might not be bad. the cap can be ordered as a separate part

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1981 NA 300D 310k miles

Just drove the car with the Mighty Vac [MV] hooked up and pumped it up to 15-20 during shifts and, to echo tons of other posters on this forum with similar experiences, IT WAS LIKE BUTTER!!!!

HOLY COW MOOOO!!!!

Enough silliness. Really glad I bought the MV.

Leak is definitely either the line itself or the modulator is bad or that cracked cap perhaps is the culprit.

That problem goes on back burner as I attempt the valve cover gasket change.

Thanks Sleepstar. Will do that.

Well you have proved to yourself and many others, that vacuum does not control the shifting. The vacuum modulator is there to smooth out or to soften the shift. Your transmission appreciates a hard shift, but people don't. Anyway, always make sure you have adequate vacuum for stopping. You really stop the car without it. Nobody wants an accident.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!