Hello. My car just started SLAMMING gears lately, so I knew it was a vacuum leak of some sorts.

I got out my mityvac and pulled vacuum on all the lines coming from the vacuum pump. I pulled vacuum on the line going to the vacuum control valve, it was leaking slow. I pulled the line going directly to the tranny, it held vacuum fine. I pulled a vacuum on the control valve itself (with the other ports blocked off), and it was leaking slowly.

Is this my problem? The vacuum control valve? Im assuming it should hold a steady vacuum. I just want to make sure before I order a new one.

thanks

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93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K

It's hard to test the VCV. It doesn't hold vacuum, it's a controlled bleed system. It should get about 25" vac input from the engine, and the ouput is approx 15" at idle, dropping gradually to zero at WOT. You can't really test this without applying a steady vacuum source, though (not a MityVac). I would measure the vac out the output while driving, see if it varies from 15-0 or not. If it does, you have a leak somewhere else (check all fittings, etc). If you're getting 25" in but near zero out all the time, yep, that sounds like a bad VCV. Now, if you're getting a proper signal output... and the tranny is still acting up... it could be a bad modulator at the tranny.

FSM links:

http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/07.1-1826.pdf

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