Everything seems to be working fine now....just trying to figure out what's going on.

1. Took the 1991 300D in for glow plugs.

2. Tech said he noticed that a vacuum line (from actuator in front of coolant reservoir to turbo) was disconnected, so he reconnected it. Whether it was knocked loose by someone else or deliberately disconnected, I have no idea.

3. Drove the car away and noticed very weak acceleration.

4. Disconnected the vacuum line and acceleration came back but now noticed that I had no AC coming out of center vents....obviously a vacuum problem.

5. Tech found that he had knocked a line loose in the area near the glow plugs. He reconnected it.

6. Now, with the second line reconnected and first one disconnected center vents came back but only intermittently.

7. Played around with it for a while (15 minutes), reconnected first line, and now all is well: have both my acceration and consistent center vents with all lines reconnected.

Can anyone help me understand what was going on here?

Do certain parts of the vacuum system take longer to regain pressure than others? I was having trouble figuring out why, for a while, the center vents worked only intermittently.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife