Someone please clear this up for me : vac valves on top of Valve cover, EGR AND tran? - PeachParts Mercedes-Benz Forum

MattBelliveau · #1 11-03-2005, 12:37 PM

Could someone please clear this up for me. Those 3/2 valves that sit on top of my valve cover, do these control EGR AND tranny, or just EGR? I'm nearing the end of my tranmission vac problems, and I need to know.

81Wagon · #2 11-03-2005, 12:42 PM

Just the EGR. The tranny is controlled by that white vacuum valve hooked up to the throttle by the IP.

When I removed my EGR I removed the 3/2 valves and all the associated garbage, everything looks much neater now

.

MattBelliveau · #3 11-03-2005, 12:46 PM

Excellent. My tranny problems are solved! Shifts nice and smooth (but not TOO smooth); no whiplash, no banging, not tire chirps at 1-2 shift, no flaring! Thanks. On to the next project.

propigskin · #4 11-03-2005, 02:26 PM

I thought those little white finger looking valves on the valve cover control the transmission. Can someone post a pic of what they removed on top of the valve cover? ive got a 82 300td

tangofox007 · #5 11-03-2005, 02:35 PM

Quote:

Originally Posted by propigskin

I thought those little white finger looking valves on the valve cover control the transmission. Can someone post a pic of what they removed on top of the valve cover? ive got a 82 300td

It is not essential that the valves be removed. Just disconnect the vacuum line to the valves, plug the supply side and those valves will stop causing problems. A one-minute job, counting opening and closing the hood.

propigskin · #6 11-03-2005, 03:58 PM

So basically i can rip the whole black box off (including the tranny valves), plug the supply line and everything will be okay?

thanks
erik

tangofox007 · #7 11-03-2005, 04:16 PM

Quote:

Originally Posted by propigskin

So basically i can rip the whole black box off (including the tranny valves), plug the supply line and everything will be okay?

thanks
erik

They are not tranny valves!!!

propigskin · #8 11-03-2005, 05:05 PM

I always thought those little white levers are for the transmission. That is what they are listed as on the dieselgiant.com

Breckman99 · #9 11-03-2005, 05:31 PM

One of those valves IS for the tranny and is pretty important! Look up some diagrams for more information. I once unhooked all those lines and found out one is crucial to proper transmission adjustment.

Breckman99 · #10 11-03-2005, 05:34 PM

Well I didn't realize you were working on a D. I am not sure if the same system is applied to this model.

Old300D · #11 11-03-2005, 06:12 PM

Quote:

Originally Posted by Breckman99

One of those valves IS for the tranny and is pretty important! Look up some diagrams for more information. I once unhooked all those lines and found out one is crucial to proper transmission adjustment.

No, not even on the SD. DieselGiant is mistaken, the 2-3 valves are for the EGR only. Check the service manual, and other online references, the transmission modulator vacuum is controlled by the injection pump valve only. There is raw vacuum to the 2-3 valves, and the only outlet goes to the EGR valve.

If repairing these valves improves your shifting it's because the leak was large enough to affect the level of vacuum in the distribution hose.

propigskin · #12 11-03-2005, 07:23 PM

So basically, take the whole box off the valve cover and plug the supply line?

any pics would help..thanks!

pawoSD · #13 11-03-2005, 07:23 PM

I think mine leaks, my shifting is not always perfect....can I just take the lines off that air/valve box on top and plug them? My EGR has been long disconnected.....

I think I also need to adjust my bowden cable, I'd like it to draw out shifts longer like our 83 does.....

When barely on the throttle does going into: 2nd at 8mph, 3rd at 16mph, and 4th at 22mph sound right? it holds them longer if I actually press it (1/3 of the way)....it becomes.....2nd at 15mph, 3rd at 28mph (roughly) and 4th around 40mph. Sound right? It just seems like the 83 holds them out a little longer when given the same amount of throttle....

Breckman99 · #14 11-03-2005, 07:24 PM

Well! After a small amount of research I was proved wrong! It seems the system on my car is installed completely wrong! Thank you for the insight. I found this site helpful:
http://www.continentalimports.com/ser_ic20242.html

When I get back home it will be a retune for the tranny!

nhdoc · #15 11-03-2005, 10:19 PM

I can only tell you that on the 240D (W123) there are two of those vacuum switches mounted in a black box on top of the valve cover. One of them controls EGR and one controls vacuum to the modulator on the transmission. You can follow the lines to determine which is which. When I bought my 240D it shifted very hard and it was because the valve was leaking badly and no vacuum was being applied to the transmission modulator (in essenece the tranny thought the car was always under full throttle). I tested the modulator by hooking up a mityvac to the line to the modulator and applied a couple of inches of vaccum to it, which it held and then went for a drive. The shifting was smooth as butter. Then, if you apply even more vacuum you can get the transmission to flare between gears. It's kinda interesting to play with. Anyway, when the valve is working properly it sends vacuum to the tranny to tell it what vacuum would be on a "gasoline" engine...WOT=no vacuum, idle and low load = high vacuum.

Having said that, I would assume the 300D is the same but don't know for sure...still if you see a vacuum line running down to the transmission from one of those valves you can bet it is the same as my 240D.