I am trying to fix the shift problems on my 300D Turbo Diesel Transmission. When I try to pull a vaccum reading on the black line running to the modulator on the transmission I cannot get a reaing. I am using a hand operated vaccum pump. When I test the vaccum coming from the vaccum pump with a vaccum guage I get 20 - 25.

Also, the clear plastic vaccum hose is brittle and cracked in several places and the previous owner sleeved it together with a larger diameter rubber vaccum hose. Is there a source for the MB spec vaccum hose that is reasonably priced and do I need to know specifics about diameter etc when I order.

As Always,

Thanks,

Dave

MB 300D 1983 Two weeks in still having fun.

First check your kickdown switch under your gas pedal (I learned that one the hard way). Check my posts by clicking on my name. I made the mistake of going at my vac system willy-nilly; dont if you are doing the same. What are the symptoms exactly and people will help? Look at fastlane and performance products for vac hose. There's tons of prelim. information here to research re: leaks, proper pressure, cracked mod caps, vacuum control valves, etc.

The vacuum line to the mod. could easily be unplugged. After so many years under the car, the rubber hose that connects to the mod. deteriorates and can loosen up. Your mod. should hold vacuum(14Hg?).

I had the same problem. As soon as I got under there and replaced the flexible rubber line between the hard vacuum hose and the modulator it held vacuum.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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Yes, you need to go underneath the car with your vac tester and test AT the modulator. If it holds at the modulator, then work your way back under the hood and fix/replace the offending line. If it won't hold at the modulator, replace the modulator. They do go bad.

Proper diagnosis is the key.

Hope this helps,