I am about to start searching for my problem.

Shouldn't I be able to search for the problem with the car in park and running. I don't see why it would be necesary to vacuum test the system while the car is driving since I'm just searching for where the vac is lost. Am I correct?

Yes you can test for vacuum going into the VCV (and all prior points)at a standstill. You'll have to test the output of the VCV while driving though, I think since you need to open the rack to see how the VCV responds.

Conceptually what the VCV should be doing is mimicking the behavior of vacuum in a gasoline engine under various load conditions.

Yes. You can search for your vacuum leak with the car in the driveway.

Tried and trued sequence
 

x2



nckmsn - modulator is last period.

There's a sequence to the testing of the vacuum system repeated ad infinitum in the multitude of vacuum related threads turned up via search. This article is priceless insofar as chasing down vacuum issues: everything mapped out. Here is another: http://www.peachparts.com/shopforum/diesel-discussion/158216-its-critical-how-you-set-your-transmissions-vacuum-system-your-diesel-mbz.html . Now that you've invested in a vacuum pump, you are on the path to enlightenment. It will prove to be one of the wisest "investments" as an diesel benz owner. Oh, and highly doubt the pinching of the vacuum line will have an effect unless you are seriously clamping down with your fingers or some other implement. Simply folding over of the clear tubing is irrelevant. If you're concerned about this get some rubber/fuel hose from the local parts store if you don't already have some. I've sourced 5/32" hose at local parts house which is one or two thousandths smaller than the 4mm MB spec., if I'm not mistaken. Six feet will run you less than a ten spot. My hh vacuum pump is on the perma-ride-along for a couple months now as I shake down various parts. It has commandeered the vent line into the cabin at the end of the previously mentioned hose. I always know the vacuum just downstream of VCV, clip off a length of hose whenever needed...you get the picture.

Luke, may the search be with you.


FNHB

Thank you for the post!. I agree now that I have the vac I can utilize the search function!

I am going to test and report my findings shortly as I dont have to go to work today!!!!!!!

Okay. So the line going into the top of the vcv tees and one line goes into the top of the vcv and the other line goes to the transmission. Assuming this is set up correctly I have the following results.

At idle in park I get a reading of 17 going into the vcv. Then the line going to the transmission reads maybe 1. It looks like the vcv is leaking and stealing the vac from the transmission. It makes sense that the vcv would have the ability to regulat the vac from high to zero, but should it be sending no vac to the transmission at idle. Also when I rev up the motor the vac line to the transmission remains at zero. Maybe you have to be ingear for the line to the transmission to have any vac.

Is my vcv shot?

if i can put up with it,wouldnt i want a nice firm shift?i like the chirp of first to secong gear shifts when accelerator is on the floor too.is there less wear on the trans the less time it spends between shifts?does milage come into play here when firming shift???
What are the pros and cons of just disconnecting the vacuum line before the transmission and plugging it?

Trust me, you wouldnt want to drive a round that much with as hard as it shifts. It is not firm, it is very hard.

Should I pull the vcv to inspect?

I presume that you removed the line from the VCV and attached the gauge. At that point, the reading was 17.

Then you reconnected the hose to the top of the VCV and disconnected the line to the transmission. You then connected the gauge to the end of the T where the transmission line had been.

If I am correct in these assumptions............because your posting details were inadequate...........then the VCV is shot and must be replaced.

Yes you are correct in my assumptions. I have removed the vcv and determined that it leaks. What are members doing to replace these since they are no longer available? Also, I remember reading a thread where someone was actually taking the vcv apart to repair.

Is the vcv from a 123 and a 116 the same or interchangable?

x2

Hmmm. Just re-read his post and initially I had a different interpretation. Yours is more likely correct, though.

What I pictured was his mityvac connection to the tranny being directly to the line down to it. Proper TS procedure would be taking a reading at the line exiting the vcv before moving on to the hard plastic line to AT. I would start by correctly adjusting the vcv before pronouncing its demise. It could be that the linkage is set to where it is actually leaking out and never passing any vacuum. Then check the hard plastic vac line dropping down to side of tranny. Pull vac on it to see if it holds. Be prepared to replace rubber fitting at modulator, you'll understand when you get there. Think constant bombardment from anything escaping the engine bay and also anyything kicked up from the road along with the usual suspects, heat and age and whatnot.

NCKMSN - Did you at least read through the first link above. If this clicks the rest is icing.


FNHB

Ahh...timing
 

Was posting at the same time as you. Try the linkage adjust in my previous posting. Don't call it prematurely, these are not very easy to come by in working condition. Still possible, just time consuming if anything. If you do need a replacement, I have a couple in superb condition. Let me know and we'll work something out.


FNHB

Yes I did read throught the link. I ended up removing the vcv and added vac to it with the cam in all positions. It leaks in all position too much for any vac to go to the transmission. I am now going to the local vintage mercedes junkyard to buy another vcv for $10.

Where did you pull the vac from, it isn't clearly stated. If you are trying to pull vac through it with the handpump, notgonnadoit. You're correct though about leaking in all positions excluding full closed, ergo my linkage suggestion. The diesel's vacuum pump will provide constant and adequate vac to test the vcv and this can be done without removing it from the ip. You'll also witness the scale of leakage on the mityvac guage, as it increases. Just disconnect the linkage that drops down between the ip and block and connects it to rest of throttle linkage. No offense but your readiness to jump on a purchase, no matter how minimal, seems a bit quick and in the end may not accomplish anything positive. If you insist, though, good luck with your trip, I do hope you find one.



FNHB