Rocketman – I want to see IF I can help some here and I think it’s best IF I expand it by starting each sentence on its only line, underline the parts I’m responding to and then inject my comment(s) [in purple color] and question(s) [in red color] afterwards. Lets see how this works !? I just noted that you just recently joined the MercedesShop.Com FORUM in Dec, 2008… welcome !
First let me compliment you for doing your “due diligence” / homework before posting.

Note that I have 3 questions above in red that I’d like your responses to…
especially Q1 & Q2 after line [1].

So now where do I begin so I might do some good!...

Q4 – Did you clean out inside of any lines… and particularly the orifices [ #62 & 63]… did you try to loosen up and clean out the VCV?
I like to spray carburetor cleaner into such parts that have plastic/rubber parts and then blow them out gently. Remember that the air flowing in these systems is introducing dirt and this carries towards the vacuum pump… so general cleaning is VERY important. I bring this up because of your mentions of the orifices as noted above! Later maybe we can talk about installing in-line paper media fuel filters to help keep the system clean.

Q5 – In [7] above, why did you choose to add a green orifice [ 0.7mm – the smallest] at the start of the system at the Vac,Pmp-to-Brake Booster line? If I’m correct, these orifices are used to balance Engine/Tranny-Shifter Vacuum Control system so that then the bleeding effect of the VCV will adjust the vacuum being sent to the tranny modulator is close to that of a gas engine’s manifold vacuum when you work the throttle.

At this point my specific recommendations are as follow :

(1) As best you can, please answer my questions above.

(2) Unless you have already done so, I would remove the VCV from the car by unbolting it and disconnecting the plastic sliding latch on the linkage rod that is connected to the throttle linkage that is between the IP and engine block. Completely remove it from the car.

(3) Before doing any cleaning, first gently blow through the VCV using a clean hose connected to the vent connection… and NOTE the VCV’s resistance/flow characteristics as you rotate the linkage lever on the back side… note these characteristics for reference and comparison later after you clean. Also note whether you can feel spring tension/resistance as you rotate the linkage lever. Any adjustment that might be needed at some point in the future would be adjusting the tension of the spiral spring that is also inside the chamber. More on this as/IF necessary.

(4) Clean the VCV by spraying carburetor cleaner into the vent connection and gently blowing the cleaner on through the valve while working the mechanical linkage lever back and forth.

(5) Once you figure you have it dried out inside, then use something that will server to soften and condition the rubber/plastic seat that is inside the chamber… maybe silicone or even Armoral… and once again gentle blow through it while again working the linkage lever !

(6) Again blow gently through the VCV and make a mental comparison with before you cleaned it as to it's flow and resistance charateristics while blowing .

(7) It might be helpful IF you can give us a macro/closeup photo of the VCV while it's out of the car... front and back!
There are different types!


I think I have given you too much as it is… so try to complete the above and report back to us ! Regardless of my having written all of the above, DO NOT LET THIS cause anyone to hold back any ideas you want to interject... please!


Regards,

Thanks for responding SMR.

I will start by clearing up the confusion that I left with my previous posts and answering any of your questions that I can with the information I currently have at hand.

Q1) and Q2) By information and belief, mileage for both car and trans is 145681. When I purchased the car in 2006, it had a working odometer that showed about 135K miles. However, when the odometer was set to rollover to 140K, it rolled to 240K instead. The odometer now is inoperable possibly due to speedo cable failure. The condition of the rest of the car (pedal wear, seat wear, etc.) is consistent with 145K.

Q3) I replaced the green dashpot as part of an overhaul of the vacuum system. Generally speaking I have replaced everything that I could, as long as the item was fairly inexpensive (check valves, connectors, dashpot, yellow splitter valve in lock circuit, lock master switch, thermal vacuum switch, 3/2 valves and levers (mine has 3)). I had already thought of putting the old dashpot back, but the trashman has it.

Q3a) The yellow orifice at 63 was not blocked, but I did try the new yellow orifice and the new blue orifice with no qualitative improvement to the shifting problem. The original yellow orifice is back in place.

Q4) I have been through the entire vacuum system with my handheld pump and all lines are open, to the best of my knowledge. The items that are supposed to hold vacuum (EGR, transmission modulator, VCV) seem to hold it or only leak down very slowly. Note that all these tests were performed with the engine off using the vac pump as the source.

Q4a) I have not removed or disassembled the VCV. I have only shot high pressure air from my compressor into the various ports (I did not overpressurize as the air source was only blown into the ports and was not actually hooked up to the ports).

Q5) After reading the Brotherton article, I noted on page 3 of 6, second paragraph, that he identified a common cause of flaring as high vacuum due to too large or no orifice restriction at 62. I also noted several posts in this thread that seemed to indicate the orifice as a mighty warrior in the battle to fix the shifting problem. I tried both the blue and green, with the green seeming to make a small, qualitative improvement. Since the effect was small, I conclude that the orifice in the Tee is approximately the same size as the green orifice I installed (green orifice remains in place).

General comments in response to your comments.

C1) My VCV is the model that includes the adjustment screw concealed behind the domed plastic cap. Based on the condition of the screw, it has clearly been abused in the past and will not turn, even with considerable torque applied via pliers (slot has been ruined and will not accept screwdriver blade).

C2) The VCV valve was tested without the engine running by using the handheld vacuum pump to apply vacuum (15 in Hg or so) to the top port (where the line to the green dashpot attaches) and then actuating the throttle cam by hand. Vacuum broke and fell proportionally with throttle position. I could also see small step changes that I attributed to the 3/2 valves as I watched the throttle cam actuate them. So, despite the abuse, the VCV does seem to work, in simulation if not in practice.

C3) The tranmission modulator valve was tested using the handheld vacuum pump as the source, attached at the 'b' leg of the Y connector at/near item 71 on the schematic. When pumped up to ~20 in Hg, the vacuum decayed very slowly - taking approximately 5 minutes or so to bleed off. So, no serious leaks here.

C4) The vacuum system, as it was when I purchased the car, had both the HVAC and LOCK systems blocked off and the 3/2 valves were leaky and/or not funcitoning due to worn levers and leaky connections. The previous owner may have tried to compensate for this by 'adjusting' the VCV - thus the abused adjustment screw. Shifting, especially when cold, was delayed and rough in 1/2 and fairly early, but smooth with no falring in 2/3 and 3/4. When I began to rework the system and 'fixed' all of the things mentioned above, the shifting became smooth in 1/2 and badly flaring in 2/3 and 3/4 while all transitions occurred at RPM that was too low. I would be in 4th gear at 15-20 mph with no means to accelerate. At all times relevant to this investigation, the transmission has been very reluctant to downshift and the kickdown switch has been ineffective or inoperable.

C5) When I performed the driving test, the handheld vacuum pump was Teed off from the 'b' leg of the Y connector near schematic item 71. The behavior of the vacuum did not indicate a linear reduction of vacuum with throttle position, as the vacuum seemed to fall to a relatively low value (~2 in Hg or less) as I drove up the hill to get out of the driveway. All shifting seemed to be occurring with vacuum readings that were fairly low, despite throttle positon. This led to my experiment with blocking off the VCV vent port and the associated qualitative improvement. This also seems to indicate that air is leaking into the VCV some other way.

C6) I will attempt to clean out the VCV and report back.

Thank you for your help in this matter.

Unfortunately, certain folks are wasting time and resources steering you to a vacuum problem when their understanding of the system is not comprehensive.

Understand this clearly:

Once vacuum to the transmission has fallen to such low levels (2-5" Hg), the vacuum system cannot fix the flaring. Flaring occurs when you've got too much vacuum. So, chasing vacuum issues at this point is a complete waste of time.

You've got two possibilities:

1) Get under the vehicle and increase the modulator pressure with the adjustment handle. Three turns clockwise on the handle and then take it for a drive.

2) Purchase the superior shift kit and replace some springs inside the valve body. This is not for the faint of heart and requires pristine cleanliness.

where can I get the shiftkit?

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Rocketman,
I think Brian's idea about adjusting the vacuum modulator is where you need to go NEXT for you have NOT mentioned adjusting the modulator in what is obviously your very thorough effort thus far to refurbish the vacuum control side of the "total system". AND your mention of the kickdown not working also sticks in my mind!

We could hold a "chicken-or-egg" argument as to where you should work first but this THREAD was started on the premise that these Engine/Tranny-Shifting Vacuum Control Systems [E/T-SVCS]... these systems were a far greater mystery to me at first and thus as I began to understand their importance on my much simpler 1980 model systems, I then started this THREAD to point out what turned out to be my problem with my car and its newly rebuilt transmission. I’m proud now I did this for this THREAD has proven extremely popular...
[now 53,000+ hits]!!

Thus Rocketman, I still think you were wise to make your considerable effort refurbishing the much misunderstood vacuum control side of the total automatic shifting system(S)… but Brian is correct in that IF you have not started adjusting the vacuum-to-hydraulic modulating valve that is on the tranny, then you have NOT addressed an IMPORTANT part of your total project.

For me I started out by first adjusting the modulator to both extremes [ in and out] all the way and in the process of doing this I counted the number of full turns this takes. Call this "adjustment lattitude". I think it turned our to be 20 to 25 turns. Then I adjusted it back to a mid-way position. From there because my tranny was flaring badly I adjusted the modulator 3 full turns at a time "IN" until I saw improvement. Then I began to make smaller and smaller adjustments. But I was working with a $2,500 rebuilt transmission that the young installing mechanic had completely botched the vacuum plumbing because he tried to use a 1982 diagram and also just did not have the patience or inclination to learn a logical method of first getting the vacuum control side resonably correct first before adjusting the modulator.

YOUR OLDER tranny might work out differently when you get into this IMPORTANT part of your fix. With the still relatively low mileage on your tranny, I am hopeful you will see real progress soon once you doe as Brian is suggesting… and then later you might find it necessary to go back to further checking out the VCV. Believe us, on trannies that are [shall we say] "broken in", you will find yourself back under the car many times before you get things just the way they need to be. I must have done this ~10 times!

Again, congratulations for your work thus far...

But as I closie this, let me do so close by relating an incident I just experienced with my Son's 1980 300D. It suddenly started shifting very poorly with much the same symptoms as you have described with your 1981 model. This was immediately after I had done a oil/filter service and so I was naturally suspect that I might have knocked something off or loose. Sure enough, the mechanical link rod between the VCV and throttle/idle linkage connection point had some how come completely off so the VCV was static... NOT working at all and the static bleed position it was in was what the vacuum side of the control system had to use ! I relate this incident to temper and yes, counter, Brian's idea about the vacuum side of these very common E/T-SVCS problems... the vacuum side is never responsible for the sifting symptoms you have described... the flaring shifts.

Regards,

............thereby resulting in very high vacuum to the modulator at all times with the expected flaring occurring on the 2-3 shift.

Said condition is completely opposite to the current condition stated by Rocketman...........but, thanks for your contribution.

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=2&Product_Code=S68165D

I have been reading the DIY trans links for some time. I still do not have a cohesive understanding of how these transmissions should shift (feel) when properly functioning.

What exactly are the limits of a verifiable flare?

My concern stems from well-timed, but often unnoticeable shifts characterized by an imperceptible change in RPM.

I routed the vacuum system at least twice, I believe I have the proper orifices in the correct spots and my VCV reaches within its stop limits @ WOT.

My next step is to take some vacuum measurements... where should I begin?

__________________

Find the line to the transmission. On the '85, it's probably coming from the blue flying saucer on the driver's fenderwell. Or, it could be coming from the VCV directly if it's an older build.

Get a vacuum gauge and T into this line. Route the vacuum gauge into the cabin and take it for a test drive. Observe the vaccum levels at various pedal positions........idle........1/4 pedal........1/2 pedal.........3/4 pedal........and full pedal.

Report back with results.

I can do that with the gauge on the Mityvac, correct?

And does the trans have to be @ OT?

__________________

Correct.

with the trans @ OT?

__________________

explain.......??

Will I need the trans @ operating temperature before I can take legitimate readings? Shifting changes after warm-up.

__________________

It would be preferable.......you'll need more pedal when the engine is very cold.