dampener thing in throttle linkage

[Joe]

What is the device that controls retraction of the throttle linkage? This sits on the intake manifold and has a spring and bellows on it. Mine is clearly shot. Is it necessary?
Joe
1965 manual tranny

[rwmastel]

Not sure what you mean.  Do you have a picture?  How about a part number?  Can you write a more detailed description of how it looks or what it's attached to?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[A Dalton]

As you have noticed, it is a decel linkage damper.
 Called a DASHPOT.. the adjustment is for the link to be just Off the end pin when the throttle PLATE is at 4 degrees open.

[hands_aus]

Hi,
I could be wrong but I think the early cars did not have the dampener.
It is missing from my early 250sl, 1967.

Bob (Brisbane,Australia)
early 250 SL, RHD

[George Davis]

I don't think the dashpot is absolutely necessary, as mine is shot too, but I suspect it would be helpful in getting smoother shifts at low rpms by keeping the revs from dropping too fast.  It probably reduces emissions a little bit, too, as the CO and HC emissions on my car jump up when the throttle is closed.

Trouble is, these dashpots aren't as cheap as they should be and in my limited experience they don't last very long.  I may replace mine and see how long it lasts.  If it has to be replaced every year or two, maybe that isn't too bad.

George Davis
'69 280 SL Euro manual

[rwmastel]

Anyone have a picture of this dashpot?  How do you know that it's bad?  Is it a visual inspection?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[230SL67]

This device on my automatic maintains the idle speed when sitting at a traffic light with the car in gear, otherwise the idle speed is too low.  It is also found on cars with A/C, same purpose.

Chris

[George Davis]

The dashpot (if I did this correctly).  I think it's only found on manual shift cars, the automatics have the constant idle solenoid.



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George Davis
'69 280 SL Euro manual

[Joe]

The plunger on mine is very easy to push in by hand, and sticks closed. I think it is obvious it is not doing anything, and wonder if I really need it. My car is a Euro model, 1965, manual, so its use to maintain engine speed at idle and its contribution to decreased emissions do not apply. Also, I do not have air conditioning. It may be that it was added as a requirement when the car was imported to the US.?
Its interesting to me that Bob does not have one. Does anyone else here with a 230SL not have this device at all?
Joe

[George Davis]

Forgot to add this:

the purpose of the dashpot is to slow down throttle closing for the last little bit of travel.  It's basically a pneumatic damper, has a rubber diaphram inside.  If the throttle just snaps completely shut when it's released, the dashpot isn't working.  When the engine is revved and the linkage released, the engine should not return to idle immediately, but should gradually slow to idle over a couple of seconds or so.  I'm sure there's a spec in the BBB, but I don't know it off-hand.

George Davis
'69 280 SL Euro manual

[Cees Klumper]

This "dashpot" is very different from the constant speed solenoid that is found on the automatic and A/C-equipped cars which some of you have referred to. This latter item is an electrically-actuated device which raises the idle speed when the car is put in gear and/or the A/C is actuated, in order to compensate for the additional strain on the engine.
My understanding is also that the dashpot for manual cars is to prevent the throttle from returning to idle too quickly. I have two of these and one is operational, the other is shot. They cost around $180 here in Holland which seems steep for such a simple device.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[A Dalton]

I have seen more without the dashpot than with..
 And I think they take a lot of the shock wear  out of the linkage , specially on a stick shift.
 The ball joints take a beating without one , and tight links are a MUST for calibrated A/F metering on mechanical FI.

 That, aside from smother shifts, would seem to me to be better with one than not....

[hands_aus]

George,

Given your last statement, I think an auto would benefit from a dampener too.
I think my car is original but who knows?
It is nearly 37 years old (10th May) and had 2 previous owners.

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Ben]

My '64 Euro manual has one.......and it works too !

You can feel it if you rev the engine and whip your foot off the gas pedal, the revs drop to about 1000 and then slow drop further !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[Naj ✝︎]

I think you need the damper for two reasons:
1. Allow time for the idling circuit to take over air flow from the main manifold.
2.If the throttle plate is properly adjusted, you wouldn't want it slamming against the throttle body each time you lift the pedal.
Just my $0.02
naj

65 230SL
68 280SL

[George Davis]

I've seen similar dashpots on other cars but they were always shot... leading me to believe they generally have a short service life.  I'm amazed that Ben has one that works.

I think A. Dalton and Naj raise some good points as to why it's desirable to have a working dashpot.  I did a little searching yesterday and located a company that sells a similar-looking dashpot for a good price.  I may order one, and if it works out well, I'll post it here.

Bob, I think the automatics might benefit, too, but as far as I can tell, dashpots were not fitted to automatic Pagodas and there is no provision for mounting them.  Joe, Dan and others would know for sure.

George Davis
'69 280 SL Euro manual

[Ben]

Do manual transmission cars with power steering, or A/C or both have the dashpot or the solenoid ?

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[Cees Klumper]

AFAIK manual cars with A/C also should have a constant speed solenoid.

It would not make sense just for the power steering, since that is always working (so that the idle settings will incorporate the drag on the engine for it as well as for the alternator etc), as opposed to the A/C which can be turned on and off.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[Ben]

Ahh yes .......thanks Cees !

thats one less thing I need to worry about !!

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[George Davis]

Follow-up, a cheap dashpot alternative.  I ordered a $21 dashpot from Pony Carburetors ( ponycarburetors.com ) that fits 1963 and later 2100 and 4100 carbs.  It is similar in appearance to the old dashpot, except that the push rod that contacts the linkage is too short, and the mounting stud is also too short.  And the threads are 5/16 SAE, too.

But, the new dashpot is made by the same company as the old, and I was able to simply pull the push rod out of the old and press it into the new, using the old longer spring and dust boot as well.  The too-short mounting stud is more trouble, but by: (1) shortening the stud about 3/16 inch, (2) screwing a coupling nut, shortened to about 5/8-3/4 inch onto the stud (basically converting the stud from male to female), and (3) screwing a screw and jam nut through the mounting bracket and into the coupling nut, it can be mounted.  Adjustment is made by shimming with washers between the coupling nut and mounting bracket.  I'll try to post a picture one of these days.

At any rate, a cheap, slightly unoriginal but functioning dashpot can be had for $21 plus $5.50 shipping (at least for US owners), plus a little hardware and a half-hour's work.

George Davis
'69 280 SL Euro manual

[Joe]

George, have you seen any difference in how the car performs?
Joe

[George Davis]

Joe,

the dashpot just slows down how quickly the engine returns to idle during a gear shift.  In around-town low-rpm driving, shifting is a bit smoother because of this.  Otherwise no difference.

George Davis
'69 280 SL Euro manual