Car down! Need help sourcing Vacuum Control Valve VCV '84 300SD W126 - PeachParts Mercedes-Benz Forum

bodyart27 · #1 06-28-2014, 11:51 AM

Howdy! I was just looking at my User stats and it's been almost 4 years since I've posted. I used to be a rabid "How To" contributor. Then I went off and started a business and had a child.... well you get the picture (no more free time).

So, the real reason for the post is my '84 300SD W126 needs a Vacuum Control Valve or "VCV" and everything I'm reading says the part is no longer made. Part numbers look like it can be either 1230700046 or 6170700246. I could REALLY use a lead on sourcing good one as it's sidelined the car (shifts very hard and I'm afraid it's going to trash the transmission slamming up and down gears).

I've done quite a bit of testing - great vacuum supply up to the "T" to the VCV and off to the transmission. Tested line to transmission - no leaks, replaced rubber where it joins to transmission to make sure I'm not losing vacuum downstream to transmission. MityVac attached to the top of the VCV - won't hold vacuum and the vacuum does not vary when I move the throttle. When I "T" in between the VCV and the transmission with a gauge I get super low levels (almost none) and again no change with throttle or monitoring while driving around. I've adjusted the VCV with the 8mm nut on the front but it's making no difference in performance. Years ago I've tested at that point before when I tuned my transmission shifting and used to get in the "teens," now it's reading like 0-3. Seems like the VCV is not operating and bleeding off way too much vacuum so I can never get an adequate supply to reach the Transmission to soften the shifts.

Any leads on where to get a VCV in good order would be appreciated. Hopefully someone has benefited from one of my "How Tos" write-ups and can return the favor? Scouring eBay the past month and no luck. If you have one for sale please email me info@shellblack.com - Thanks everyone!!!!

JimmyL · #2 06-28-2014, 11:55 AM

Cleanest SD you will EVER find!!!!!!

bodyart27 · #3 06-28-2014, 12:00 PM

I should have figured you'd still be on the board. Mechanically the car has been well maintained, unfortunately the clear coat let go two years ago. Her sad exterior appearance does not reflect how solid she is underneath. Under the hood she still looks pretty damn good though

.
~shell

charmalu · #4 06-28-2014, 12:29 PM

Wow, two old relics from the past.

I have a few of the VCV`s. have no idea if they work, just grab them when I see them in the yards since they are NLA and I have the SD, only one with a auto trans.

Let me know.

Charlie

bodyart27 · #5 06-28-2014, 12:46 PM

Pretty desperate to find one that works so I'll give them a shot. Email at info@shellblack.com so I can send you some $$$ for the parts and shipping.

SD Blue · #6 06-28-2014, 12:49 PM

Wow! The thought came to mind that I may be responding to a several year old post!

I plugged the 1230700046 part # into Bing and came up with a couple of places that claim to have it.

MB Parts World (the dealership in Atlanta)
Benz parts wholesale (Monterey, CA )

Have you tried calling Pelican Parts to see if they have a source?

bodyart27 · #7 06-28-2014, 02:44 PM

MB Parts World in Atlanta was a bust - I tried ordering from them last week. They took the order online then cancelled it 24 hrs later saying no longer available. I'll try Benz parts in Monterey now...

Update - Benz parts monteray took the order online, but the description "VALVECARB" (and no photo) was not encouraging... fingers crossed

bodyart27 · #8 07-02-2014, 10:38 AM

Well Benz parts wholesale (Monterey, CA ) cancelled the order because part no longer available - not surprising.

I have a used part coming my way off of eBay (fingers crossed - my other ebay purchase was a dud).

If anyone has a good used one they are willing to sell let me know! (email - info@shellblack.com)

funola · #9 07-02-2014, 10:51 AM

Are they repairable? Have you tried? Take pics if you take one apart.

toomany MBZ · #10 07-02-2014, 03:09 PM

They do have an adjustment.

Remove the cone shaped thing. Behind that you'll see a two sided nut. With the car running and a gauge on the line that goes to the transmission, turn the nut, it should increase or decrease depending on which way you turn it.

Hope this helps.

Phillytwotank · #11 07-02-2014, 04:23 PM

is there a sure fire way to bench test the VCV? i too have a few laying around but no idea if theyre any good.

toomany MBZ · #12 07-02-2014, 08:08 PM

bodyart27, what is the issue?

How did you determine it is bad?

The below video shows an out of the car VCV in "operation".
https://www.youtube.com/watch?v=Yn1fj9_OTm0

If you are not getting any vacuum measured from the VCV to the transmission, check the vacuum from the main vac line.

bodyart27 · #13 07-06-2014, 04:31 PM

I've now acquired 4 VCVs (1 original + 3 eBay) - none hold vacuum as shown in the YouTube video - MB VCV operation, part #617 070 02 46.avi - YouTube

When bench testing and I apply vacuum with a mighty vac, all bleed vacuum fairly quickly from the top and no amount of playing with the throttle linkage stops it. I have one VCV that "dumps" vacuum quickly like in the video (when at full throttle for firmer shifting), but doesn't hold vacuum steady - just bleeds down quickly.

I've tried adjusting two (the little 8 or 7mm nut) clockwise to try to add more vacuum but they are "maxed" and still don't provide enough vacuum nor will it hold. I'm guessing if they don't hold a vacuum on the bench, trying to adjust is pointless?

Attached is a little drawing on what I'm seeing vac reading wise with car running:
"A" - vacuum strength before it gets to VCV -20 Hg,
"B" - vacuum strength just after the VCV - mostly -8 with an occasional -10 max
"C" - putting a "T" in between the VCV and the Transmission - "0"

So, best I can tell reading other posts - in location "C" (T between VCV and trans) I should be in the mid teens at idle - and I'm at zero to maybe 2.

So just to confirm - if won't hold vac on a bench test - bad?

tangofox007 · #14 07-06-2014, 04:43 PM

Quote:

Originally Posted by bodyart27

So just to confirm - if won't hold vac on a bench test - bad?

I don't think that is a meaningful test of the valve's operation.

bodyart27 · #15 07-06-2014, 04:44 PM

Just more of a curiosity, but I have found three part designs thus far. As "toomany MBZ" mentions there is an adjustment nut underneath that cone shaped cover. It's tough to pull off, but it wiggles straight off (no twisting).

Example 1 - there is a lock nut (7mm) that you loosen before you make the adjustment

Example 2 - the nut is welded / soldered on

Example 3 - this appears to be an aftermarket VCV as the plastic cone it molded to the vacuum attachment tree next too it. The metal throttle arm does has a 617 number stamped to it, but the plastic casing has no other marks.

Photo 4 shows the other design difference - the unit on the left I think is aftermarket (but notice the 617 stamping on the arm). My other three look like the design on the right that have a MB logo or 123 part number.

Just thought that was interesting.