Don't lose sleep over the boost system. Get a pressure actuator and be done with it. I modified a 603.96 pressure actuator to fit the 603.971 but it took bending the heck out of the bracket. gsxr might have pictures of my hack job.

My '93 SD drew shutoff vacuum from the accessory port rather than the brake booster check valve and it worked properly. Make sure there aren't leaks in the accessory line (VCV, etc.). IIRC the shutoff solenoid is the same as the overboost solenoid - flow when not energized, no flow when energized. Make sure you're using the right ports if there are 3 ports. One usually has a vented cap or filter.

Sixto
MB-less

OK, also I was incorrect about the EGR. It was removed by the PO on the engine that was in the W126. But the W140 still has it in place on the manifold and turbo parts I swapped over.

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

But with a bad transducer EGR might not be operating properly causing the ECU to cut boost. Tee a vacuum gauge into the wastegate actuator line. If you don't see vacuum to the actuator, EDS ain't happy. Again, not worth figuring out why, IMO.

Sixto
MB-less

Still have to get the vacuum nightmare sorted out between a 3.0L W126 engine, and a 3.5L W140 engine, but driveable at this point. I will say, these cars are way ahead of W126's in smoothness and refinement. But, I'm thinking the price for that is their complexity vs. the W126.

All in all, a good swap candidate. Not sure I'd do it again though. Way more work than 3.5L to 3.0L W126 to W126. But, so far, so good.

Attached Thumbnails

 

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

What does everybody here think about me making this W140 all Black (No more two tone). I've seen some later model W140's all black. I thought they looked great. Aside from the purist thing, what are some thoughts on going all black vs. redoing it factory two tone?

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D