Mercedes W114 250 Coupe - help!

[grober]

Here is a simplified version of how the throttle position linkage effects the throttle pressure acting against the governor pressure which is speed related. Under light acceleration a gear change would take place at a certain speed but under hard acceleration this change point is delayed till further up the rev range. All basically to do with the fact that in a hydraulically controlled box as speed increases hydraulic pressure increases and its how you modify /balance that increase in pressure to get the desired result in relation to road speed /engine speed /gear selected / accelerator position etc

Automatic Transmissions: Valves and Modulators - HowStuffWorks

this is a good nuts and bolts components " video of an autobox hardware.

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[grober]

Here's a picture of slightly later box where the older design regulator/control lever and rod to the throttle linkage has been replaced by the cable type familiar in later models. One of the problems is that on many 2nd hand automatic boxes [ such as your's Charles ] the control lever and rod have been removed leaving only the operating spindle as evidence of the control function.

 

[dokotela]

beautiful cars

 

[Bellow]

Thank you. A follow up question - given it is entirely mechanical (or pressure related) what is it that 'decides'?

Upshifts: Hydraulic pressure obtained from a pump on the gear box's output shaft (hence speed sensitive) wants to upshift but the pressure is opposed by detected travel of the throttle pedal (indicating acceleration not cruise required) via the modulator.
Downshifts: The reverse of the above. Dwindling pressure from the pump on the gear box's output shaft offers less resistance and the primary pump (aided by the modulator' input if the throttle is depressed) wins the day and forces a downshift.

A system of opposing forces with the modulator relaying the driver's wishes when they deviate from the 'pre-programmed' regime.


edit PS.
More normal now is to employ only one (primary) pump and achieve the same effect as a tail shaft mounted one by passing some of its flow via a speed sensitive governor where greater road speed equates with greater flow/pressure being permitted by the governor. (The twin pump analogy is more intuitive if less representative of reality)

 

[Charles Morgan]

You may also have to drill and tap a hole in the inlet manifold somewhere for that metal vacuum pipe with the banjo unions at both ends to connect in but hopefully there will be one there already just blanked off

Manifold sins and wickedness?

 

[Charles Morgan]

Spot the difference?

 

[Charles Morgan]

Made for each other

 

[grober]

a different perspective?

ps yours is obviously ?? the top one with the cam cover off and no injectors and there are slight differences in the roughly central linkage in the photos ??

 

[Charles Morgan]

Mine is the top. Just thought it was worthwhile to post one manual one and one auto one alongside, all other things being equal.

The throttle linkage to auto box has to be the next piece of the jigsaw. A clean up prior to a bit of paint removal in the engine bay (Tony sprayed the inner wings but they weren't perfectly clean) revealed a lot of disconnected wiring and piping - I think I've found the capillary heat gauge tubing and a couple of earths) does indicate that I'm pretty much there on parts, although a lot of things will need doing.

 

[grober]

Here's a picture of a diesel engine auto- I suspect the petrol autobox linkage may be similar running from the front under the manifolds where it gets a signal movement downwards from the injection system throttle body linkage. Mercedes of that era seem to like mounting their throttle linkages on the inlet manifold or cam cover. I imagine its almost impossible to see down there without the engine out of the car?

 

[Bellow]

Here's a picture of a diesel engine auto- I suspect the petrol autobox linkage may be similar running from the front under the manifolds where it gets a signal movement downwards from the injection system throttle body linkage. Mercedes of that era seem to like mounting their throttle linkages on the inlet manifold or cam cover. I imagine its almost impossible to see down there without the engine out of the car?
]

Isn't that it in both photos in post#946, nearer the engine between the manifold runners feeding cylinders# 1 and 2? It being a paralleled linkage from a pivoted part (connected to the throttle pedal), the other linkage going directly to the throttle butterfly?

 

[grober]

Isn't that it in both photos in post#946, nearer the engine between the manifold runners feeding cylinders# 1 and 2? It being a paralleled linkage from a pivoted part (connected to the throttle pedal), the other linkage going directly to the throttle butterfly?

I agree that that's probably correct. I was just puzzled that Charles's car has a manual box so would not require that linkage normally- however it may have another function?? or act merely as some form of idler arm?? it does appear to be slightly different in the two pictures ?

 

[Charles Morgan]

I think the throttle linkages are exactly the same, just different angle of the photo and elevation.

I hope finding the connection is simple, however, like the auto box vacuum line fitting, it would help with the engine and box out!

 

[grober]

In the various rather random pictures I have come across the vacuum line seems to follow the line of the dipstick tube upwards [ in some it appears to be partially clipped to it??] so this might give an indication where it "appears " in the engine compartment- If I was to guess it will attach at the "bulkhead end" of the main inlet manifold plenum chamber???

 

[Charles Morgan]

It is going to fit onto that second hole in the manifold closer to the block (in the photo I posted above). My point is that I can't fit it with the current engine and box in!

 

[Bellow]

I agree that that's probably correct. I was just puzzled that Charles's car has a manual box so would not require that linkage normally- however it may have another function?? or act merely as some form of idler arm?? it does appear to be slightly different in the two pictures ?

It crossed my mind later it was possibly for the (dreaded) D-Jetronic but pic in post#948 shows what I assume is a potentiometer mounted on the throttle spindle for it to misread from.

It is going to fit onto that second hole in the manifold closer to the block (in the photo I posted above).

Definitely it connects with the manifold interior?

 

[Charles Morgan]

Definitely it connects with the manifold interior?

No - a fiddle with some flexible wire indicated it is currently blind. When I get the manifold off I'll have a look at the other vacuum mount - both are exactly the same shape but I suspect the latter has a deeper hole.

 

[Bellow]

I though that might be the case - given there was no mention of it having had a blanking plug. Blowing through it (or not!) would be conclusive.

 

[Charles Morgan]

A quick blast with the air tool and it all bounced back - so I think it's currently blank.

 

[grober]

I would suggest there might be other more likely candidates for the port location.

The blanked off port where screw plug 12 goes?? The front end of the manifold also has a banjo type union 48 but seems to have a bleed screw from a pipe from the aircleaner?