Hi everyone, just wanted to continue the discussion in this thread.

http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/312740-wtb-w123-3-2-way-valves.html#post2884628

First some background info. A while ago I was having shifting problems and decided to check the vacuum modulator and it wasn't holding any vacuum so I replaced it and the new one was fine, but before adjusting it I wanted to make sure the vacuum system was healthy so I hooked up a gauge to the hose that connects to the modulator and I was only getting 3hg vaccum, I figured that wasnt right so I started looking for a leak.

I started at the vacuum pump and everything seems good a steady 22hg vacuum. Went through the diagram checking every single hose,connector and component and everything was good, 22hg all the way until I reach these vacuum valves, with the car idle the vacuum drops to 3hg, the same reading at the modulator. I took them out of the car and tested them and they don't hold any vacuum at all.

I took out the car for a drive again today and the car actually shifted into third but at what sounded like very high RPMs (dont have a tach) and at around 36mph, I didnt want to push it and try to shift into 4th since it wasn't shifting at around 52 mph...The shift from 1st into second is also very rough and at higher rpms than normal. I assume alot of that has to do with the very low (maybe non existent) vacuum to the modulator and the modulator not being adjusted yet.

Someone in the other thread suggested that I remove the egr system and these valves completely, is that possible on the automatic 240d? I was under the impression that on the automatic 82 240ds that at least one of the valves was critical to rerouting and controlling vacuum for proper transmission function, while on most w123 models they only control egr functions.

bump

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Firstly, you must be very careful with the information that you get on here. Many of the people just put forth advice based upon what works on their vehicle. They make the conclusion that such advice will also work on yours, even if your vehicle has a different engine.

In your specific case, the vehicle does not have a Bowden cable, as far as I know. This means that the vacuum system is utilized to control the speed of the shift and it is additionally utilized to control the shift points.

The 3/2 valves are utilized for controlling the shift points on that vehicle and removing them will absolutely put the shift points way higher than you desire.

The proper fix is to procure new 3/2 valves and connect the vacuum system per the FSM.

If you wish to eliminate the EGR, just disconnect the hose at the valve and plug the hose. While it may be possible to eliminate one of the 3/2 valves for the EGR, I'm not well versed in that system to advise.

And, for the future, be careful in what is posted on here. Unfortunately, a lot of it is factually incorrect and is simply put forth by "backyard mechanics" with no knowledge of the system.

THe information about the 3/2 valves is absolutley correct. Unlike the 617 which shift via a bowden cable, the shifting in a 616 is exclussivly controlled by vaccum. I know for I own both an 82 and 83 240D. In my case the PO had totally played with the vaccum hoses and I could not find a diagram to re-hose it correctly. I had to give up after 2 months and take it to a shop who specializes in BMW's and MB's. I had them correct the 3/2 valve hosing and adjust the shift points.
Currently the shift points are correct and vaccum goes to 0 upon pushing to fuel pedal to the floor, hence results in the car down-shifting.
The vaccum coming off the pump is correct at 22 Hg. It is spilt into two pathways. One going to the 3/2 valves and the VCV, the other going to the door locks.
The entire shifting system works by CONTROLLED air leaks, specifically controlled by the VCV on the back of the Injector Pump. The vaccum at the 3/2 valves has to be correct prior to adjusting the vaccum on the transmission and if I remember correctly these valves are connected together. When I purchased the car, the PO told me that the car had a shifting problem and flarred into 3dr gear. It did until the 3/2 valves where replaced. In my case both the 3/2 valves needed to be replaced, which was done. I used a manual vaccum gauge to measure the original 3/2 valves. They both leaked air between the plungers.
As for removing the EGR, this trick I know can be done on the 300D's. My 82 240D did not even have an EGR system installed.

I had asked about your car having two of those valves, in the other thread. I didn't mean to cause any confusion in so doing... but my 300td only has one. I see from your pic you obviously have two.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

http://www.peachparts.com/shopforum/2881868-post40.html

Thanks for the help everyone! I figured I probably needed them because like you guys said my car doesn't have the bowden cable. This is the diagram i'm using and everything seems to be hooked up correctly in my car. Is this the same one in the FSM, I really gotta get one of those..? Thanks again, hope I can find some of these valves.

oops, sorry double post...

My '80 wagon has the same set up as yours. Check for a leak at your modulator....my O-ring was bad. You can test it with a Mighty Vac

__________________
'89 300SE
'02 E320 Wagon

The 3/2 valve is used for the downshift to first gear at take-off. The rest of the shifts are controlled by the VCV, but the vacuum signal of the VCV does run through the 3/2 valves.


If there is not enough vacuum, it will shift at high rpm and very hard.

I agree with you. You say the vacuum to VCV runs through the 3/2 valve.
Or is the 3/2 valve teed into the supply line to the VCV?

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

Depends a bit upon the 3/2 valve, but the valve switches between full vacuum of the pump and the controlled vacuum of the VCV. The VCV vacuum runs through the valve; the full vacuum runs sometimes through the valve.

Were you able to find any? I have a leaky one too!

__________________
http://www.mortgagemitch.com/wheresmyheadat/
1982 240d
1990 525i