Quick question. I was wondering if the vacuum dashpot was only a single way valve. Should I be able to blow air through it and suck air into it or is it a one way valve?

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'82 240D
Currently running diesel but eventually I will French Fry her

The vacuum pots are designed to work on vacum-hence the name, but I immagine that they will work with pressure. The problem is that they are designed to work with a max. of 14 psi external press. If you subject them to internal press. you stand a good chance of blowing the diaphram off the end.

Are you talking about the vacuum check valves? Example: on a 300 SD there are two check valves (blue on black plastic) that control the door lock function and yes these are one way check valves. BTW: these are very easy to break so watch out or $10 each.

... yes the vacuum diagram for your model MBZ..
see http://www.peterschmid.com/vacuum/1977_1985/616_617_91/616_617_91.jpg
has what is shown as #72 and called a vacuum surge damper but this is also commonly known as a "dashPot". Many parts house even know and sell them as "check valves" but THE ARE NOT a CHECK VALVE... and they do not have any internal diaphragm. They are a simple air/vacuum chamber with the connectors on each end possibly serving as restricted orifices. This vacuum components are installed primarily to retard/dampen the otherwise harsh 1-2 shift on automatic trannyies. I just tested one on both our 1980 240D and 300D [ not in these car's original design] and so my experience with them is fresh, but positive. They only cost $4 -to- $10.
You should be able to blow through them and not cause any damage for there is nothing inside to damage and I don't think your lung-power is enough to damage them... it is just a hollow chamber that acts to delay the vacuum bleeding action of the Vacuum Control Valve [VCV] on the IP. The VCV is the component most responsible for simulating throttle pedal position by controlling the vacuum signal that is sent to the vacuum modulator on the auto tranny.
Good luck,
Sam

Soo thats what a "dashpot" is, thank you, I've wondering about that since that last thread Guess my 240Ds dont have any.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Stevo,
Looking at your Signature list of VEHs I note that you have a couple of MBZs that are "stick shift". There might be a different kind of "DashPot" that was installed or might be useful on these cars... however I think these are connected in the mechanical linkages of the IP and retard the throttle directly and have nothing directly to do with your manual trannies!

Sam

My understanding of a dash pot as it pertains to an automotive application is typically a spring loaded mechanical device that pushes or pulls an arm or linkage (e.g. carburetor choke pull off ect.) with an opposing force applied by vacuum or pressure. On the Mercedes the most common use of a “dash pot” that I have seen is in the climate control system for the vent door(s) controls.

A check valve is basically a vacuum delay valve that holds off vacuum or pressure for a calibrated pre determined amount of time and or lowers the amount of vacuum supplied to the component by reducing the size of the the orifice through which the vacuum passes.

A handheld vacuum pump tester with gauge is indispensable to check any vacuum related system.

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1982 MBZ 300SD Turbo Diesel- just turned 200,000- just breaking her in

Rocketman,
Wikipedia, the free OnLine encyclopedia agrees more with you than me!
Check out their definition at: http://en.wikipedia.org/wiki/Dashpot
"A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring (which acts to resist displacement)."

And as I stated before MBZ calls this vacuum chamber a "surge dampener".

Maybe we need a "Glossary of Terms" for the WebSite/FORUM... for many times I have seen where we get caught up in terms... and this is proof that this includes myself as well. I have seen parts sources call this a "dasPot" and so that's what I started calling it. There are different names used for many different vacuum parts on these Vintage MBZs and some of this I'm sure is due to translation problems.

Sam

You are right Sam, we need a glossary- Mercedes specific.

Sometimes when looking at parts in service manuals and parts catalogs there are three different names for the SAME PART- for all makes not just MBZ!

At least, this has been my experience over the years.

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1982 MBZ 300SD Turbo Diesel- just turned 200,000- just breaking her in

Yes, actually there is a "dash pot" on the throttle linkage of my "85", I'm learning all kinds of thing today

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

... when I first thought about this vintage of MBZs with stick shifts, it didn't make sense that they would have any of the many vacuum components that we know to be part of the auto tranny control system... but then I realized that just maybe these are for control of the turbo as well. Does your stick Euro 240D have a turbo... did it always have a manual tranny? These things might give us insight as to why you have that DashPot!??

Sam

Sam

My "85" is a genuine Euro, headlights to bumpers and as far as I know has always had the 5 speed, but no turbo. I think i have seen that little shock absorber looking "dash pod' on other "later" 240Ds, not just Euros. I cant really say I can tell any difference in throttle response between my two 240s (the 78 of course does't have one)

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

... Well neither of our two 1980(s) shown below had a "dashpot" or "surge damper" or "dampener" and because they both tend to give you a "kick in the pants" when shifting from 1-to-2, and because I saw that later models do have this device connected between their vacuum control valves [VCV] and the auto tranny shift modulator... well I decided to see if one of these cheap air chambers might improve and soften this hard 1-to-2 shift problem. Well it does just that, even more so than I expected. And it is my perception that it also delays the much less objectionable early 3-to-4 shifts... you know the tendency for it to up shift if you don't keep the pedal to the metal!

I'm even toying with the notion of seeing what two of these might do for the shifting... in series and in parallel.

Sam

I haven't driven to many MB automatics but one thing I have noticed about the manuals is the shift to second is difficult to do smoothly compared to gassers I have owned. Must be because the engine slows down fast and the dash pod slows that action. I'll have to have a look at the one on my "85" maybe it needs replacing. Anyway we now know a "dash pot" is not a receptacle sitting on the dash to put your nick nacks in

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Stevo,
Contrary to what the auto parts WebSite's are telling me, I predict that your "Stick Shift" MBZs will have mechanical "dash pods" that are connected directly to the accelerator linkage... NOT vacuum "dashpots" as I have just used and have been talking about on our two 1980 auto tranny cars.

Please come back and POST your findings here so I and others following this now and in the future might benefit.
Sam