Whatever you do, don't vacuum test the ALDA!

I'm guessing the plastic thing is the VCV. A slow leak on top is typical. I don't know about the bottom. It won't hold vacuum if it's a vent line.

The transmission modulator should hold vacuum. Sounds like you need a new one but at least you're weren't pulling ATF into your MityVac, right?

Sixto
87 300D

Sixto,

thanks for the warning on the ALDA! I was just about to vac test it! No ATF was pulled into the mityvac, but I didn't test it for an extended period of time, I pumped maybe 15 seconds, and I couldn't believe how fast the pressure was dropping to I checked the seal between all the hoses & connectors. So maybe 30 seconds of it being under vacuum. I guess the modulator being bad makes sense, ever since I got the car it's had shifting issues. Will buy one & see how it goes

Many thanks,
Michael W.

__________________
1984 300sd auto with 246,000 miles

Check diaphram in brake booster. With engine on and vacuum built up place your foot on the brake peddle and hold it on for 30 secs or so. If there is a leak in the diaphram you will notice the brakes now have no boost and you have to push down hard on the peddle to make them work, just as you described.