Hi all,
I've been having the slightly annoying problem with my '85 300d of excessively firm shifts. Currently I have the HVAC circuit capped, since I introduced a leak that was causing the car to not shut down. That's fixed for now (and I plan on pulling the dash soon to replace and clamp all the hoses I can.

While I was digging around I finally started "proper" debugging procedures on the system, I have 22 in HG at idle on the main line (seems good), but I noticed on the main supply line from the pump to the brake booster there is a check valve that taps into the large hose and has two smaller fittings. One of those fittings has no vacuum at idle. I'd have to assume that this is a fault, and since it ties into the transmission control system, that's likely my culprit. Can anyone confirm my diagnostics before I order a new main supply line, please?

Also, does anyone know a part number for the vacuum manifold(s) that supply the switchover valves? I'm not sure if it's a single 6-way manifold, or 2 4-way manifolds tied together

Vacuum is only used for smooth downshifts. Your tranny should upshift fine without vac; that is how it is designed. It will clunk on downshifts without vacuum.

Not sure about your switchover valve(s) question. There is only one switchover valve and it has three nipples. One nipple is open to the air and the other two are connected to vac hoses; the switchover valve tells the turbo to provide boost and when. (This is for 300SD and I assume 300D is same.) Perhaps you are talking about the VAV which is a white plastic gizmo with a dome?

Sorry, the switchover valves I'm referring to are for the HVAC system under the dash. There's 5 switchovers with a manifold to connect them together. I could probably build one out of a bunch of fittings, but would like to try to find the real part.

Sorry, not switchover valves - changeover valves.

Called vacuum pods I think.

Is this it?

Performance Analysis | Climate Control | Diaphragms | Blower Motors | Pushbutton Panels | Vacuum Door Locks | Autotemp | Cruise Control | Engine Oil Analysis | Mercedes-Benz Parts | Mercedes-Benz Club of America | Oak Ridge | Car Care - ACC Version I

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84 300SD
85 380SE
83 528e
95 318ic

^ No, that's the early (dreaded servo) version.

Changeover valves connect to HVAC pods.

Can't launch the epc right now.

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83 SD

84 CD

Thanks toomany MBZ - That's pretty much what I need, though mine is a bit different design - I think i'll just make it out of some 3 or 4 way connectors like yours seems to be. Mine uses a pair of slightly different connectors, but as long as I can supply vacuum where I need to, I think it will work.
(Also, I've found some interesting nylon hose clamps that I'm going to use on all the fittings under the dash. They're fairly inexpensive and not very bulky, so it should add a bit of reliability to the system, since all of the fittings are smooth, no barbs)

I have no idea what car that came from, someone thought I might want it.

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83 SD

84 CD