Upshift delay valve.....Where is the darn thing - PeachParts Mercedes-Benz Forum

agood · #1 06-13-2006, 08:09 PM

I have read all thru this forum and looked on alldata and I cannot find anything near the brake booster with a green vacuum line going to it...I have a code26 and trying to troubleshoot...but gotta find the thing first.

I have a 94 S500....is it some place different on this model?

Thanks

gurban · #2 06-13-2006, 09:08 PM

I've been told it is on the side of the transmission itself. There is a picture of the darn thing somewhere in the forum or on WIS. Hope that helps.

agood · #3 06-13-2006, 10:52 PM

I understood that the switch was near the brake booster and the actual valve was on the transmission....I am trying to locate the switch.

GVB · #4 06-14-2006, 02:26 AM

The upshift delay valve is emissions related only. It wont be hurting anything with the engine or transmission. It keeps the engine at higher rpm's before shifting to a higher gear so the cat heats up faster. Shuts off around 40 degrees C. The electric vacuum switching valve that gives the upshift delay valve the vacuum is located by the brake booster, the green line goes to the valve, and the black line supplies the vacuum. You can test the valve itself by using a vacuum gauge and suppling vacuum to the green line that goes to the valve that is part of the detent cable, if it holds it, it is good. Sometimes though it is a vacuum supply issue. Make sure you have vacuum going to the switching valve first. Like I said before, it is not hurting the car at all. It is just for smog only. If you need to replace the valve it is cheap and not a bad job. The valve retails for about $38.00, and you need not drain any fluid on the transmission, but you will have to adjust the cable.

mbdoc · #5 06-14-2006, 08:04 AM

When you get that code it DOESN'T mean than any "single" PART is the problem.

What that code does mean is that the transmission isn't staying in either 1st OR 2nd gear long enough ONLY in the morning(or cold start) to properly warm-up the catalytic converter(s).

That vacuum operated system needs a good diagnostic test performed.
Vacuum leaks are the most common problems.

agood · #6 06-14-2006, 08:36 AM

Thanks for the replies....but I still can't find it....there are essentially 2 firewalls in my car...one that is close to the engine....and then another that is the cabin wall. I took off the large plastic cover ( the one that hides the cabin air filter) so I could get a good look at the brake booster...and there is nothing anywhere near it that resembles a vacuum switch...There is definitly nothing there that has a green vacuum line going to it.....
Troubleshooting is my goal...and I need to resolve this becuase I have to go have an emission test.....

Anyone got a picture?

GVB · #7 06-14-2006, 10:34 AM

If you cant find the valve, find a shop. It should be a very simple fix for any shop that has experiance with MBZ, heck even a dealer can fix it.

Arthur Dalton · #8 06-14-2006, 10:45 AM

Follow the vac line up from the trans actuator. It goes to the Switch-Over Valve.. most likely problem is the element is leaking at the actuator/servo.

As GVB suggest, get some vac to the the element for testing
I just pull the two lines off the SOV and put them together.. this eliminates the SOV and ECU and gets vac directly to the tranny.. take it for a ride and see if the shift delays.. if it does , you have confirmed the servocable as OK ..

agood · #9 09-11-2006, 10:04 PM

Got the car on a rack the other day and tried to follow the vacuum line up to the swicth...but no luck. There is no vacuum line on the transmission anywhere. Any other ideas?...besides paying someone else to find it...or not.