w201 vacuum question
 

I have read that a vacuum leak can cause hard shifting. Where does the vacuum hose relating to this connect to so I can test how well the line holds a vacuum?

http://img.photobucket.com/albums/09...lepartsid3.jpg

you can see here the vacume connection at the air intake end but I dunno where it goes to.

Mike.

That goes to the modulator on the side of the transmission.

Check for vacuum at the modulator line, idling the vacuum reading on a good engine is 14” to 22”
Then check for vacuum response, a quick opening and closing of the throttle should cause the vacuum to drop below 5” then rebound to 23’ or more. . If you do not have the proper reading, follow the line up and check for leaks.

vacuum
 

What if you've checked it back to where it breaks off from the main line? How do I know if it is the pump not working properly? I feel some but not much vacuum. Thanks, Hedwig, 81 300sd

The whole point of vacuum modulators is to modulate shift pressure in relationship to vacuum, which on gas cars is directly related to engine load.

No pumps on recent MB gas motors. Vacuum is from the manifold.

diesel vacuum
 

I am wondering about the vacuum for an 81 300sd. I am talking about my last post about the vacuum pump.

wow mike, thats perfect. I had been able to find the end of the line at the yellow plastic box mounted on the trans but the hose went up over the trans and I couldnt trace it.
I will take the hose off near the intake opening and will check the vacuum. I'll post my results.

Also, I have a question about the throttle cable that goes to the transmission...
My Haynes manual wasnt very descriptive in how to adjust it, any suggestions, and what can be changed by adjusting it?

The line holds a vacuum fine.....
Could the modulator itself be bad?

I have heard that there is an adjustment that controlls the intensity of the shift... but how to make the adjustment is unknown to me. My guess would be at the modulator but then again I don't know if such an adjustment is possible on your model.

The vacuum modulator is what determines how hard the car shifts. The less vacuum the bigger load on the engine and the harder it shifts, which is why a vacuum leak would cause it to always shift hard, I just dont know if the modulator itself can go bad and cause hard shifts all the time.
The info I'm looking for is probably somewhere on these forums, I just gotta find it