Vacuum @ wastegate solenoid vs. EGR solenoid 98 E300D
 

Just when I thought it was safe to go back in the water here comes my old friend P0243 code. Turbocharger circuit A. I posted a few days ago that the problem was resolved when I discovered a rusty nipple on the wastegate that was making for a poor vacuum seal. It did work for awhile but code reappeared.

Here's what I've done so far. I checked vacuum at the inlet line from the main vacuum line to the EGR and had 27" steady at idle. Wastegate line, 5" at idle. Made me think a cracked line from the wye to the wastegate solenoid, so I jumpered it with a test line and same thing.

Next I swapped lines into the wye so as to exchange the line to the EGR and wastegate. Same thing, wastegate 5", EGR 27".

Finally I just connected a direct line to the wastegate solenoid to the main vacuum line and temporarily eliminated the wye and got 27" at the solenoid.

So my questions are: If its just a simple wye in the vacuum line why is there a difference on the wastegate side being lower? Does anyone find a similar difference in their vacuum at these points? If so, why, and what should proper vacuums be at these points?

Finally I have re-installed the wye with both lines hooked up properly and no codes yet but only a few miles under my belt so far.

As my Dad would say, "I don't think I understand everything I know about this device".
Any help and guidance would be appreciated, because I'm not too optimistic that the issue is resolved.

Not exactly sure what you are trying to explain but you should have max vacuum on the line going to the wastegate actuator (after the solenoid) while the car is idling.

I guess the simplest way I can explain it is that I have two different vacuum levels coming from the wye that connects to the vacuum manifold just before the brake booster. When I have both the EGR and Wastegate lines connected I get 27" from the wye outlet to the EGR and 5" on the one to the Wastegate.

The manifold nipple gives 27" but when I connect the wye it splits out as above. The wye seems intact and I can switch the sides of the wye but it always ends up with 5" for the Wastegate and 27" for the EGR.

You got a leak somewhere that needs to be resolved before you go much further.