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1972 350sl (4.5) 1987 M6 Euro 1995 840Cia 2012 E550
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42 Posts
Discussion Starter #1
I am in the process of replacing all vacuum componenets to my 1972 450 sl as part of an entire ground-up restoration (lunacy--yes but...). There are three vacuum switch over valves: two on the back fire wall just under the blower cover and one mounted on the radiator reserve tank support. They look like little, round, metal hats. The new valves are completely different!

The two valves at the fire wall have have three openings top, bottom (center), and bottom (lateral).

The valve under the radiator tank (which leads to the distributor vacuum and throttle) has two ports on its underside (a central and lateral port) and none on the top.

The new valves are entirely different and are stamped positions 1)-bottom; position 2)-top; and position 3)-lateral. I understand how these electrically gated valves work.

However, can anyone please give me a precise idea exactly which ports of the OLD valves correspond to the three marked positions (1, 2, and 3) on the new valves? Finally, how do I use the third valve (under the radiator reserve) and what do I do with the third un-used port? My local mercedes folks are utterly unhelpful on this.

Finally, the two-barreled electrical connections do not have a guide pin to ensure polarity. My old set up had the label on the plug facing away from the center of the valve...do I merely continue this theme? How should I re-hook these plugs?

Thanks greatly!

ps: because of the "sticky", I have already replaced all lines, connections, and diaphrams...but this is not as obvious of a direct substitution!
 

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1974 450SL, 140,000 MILES
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8 Posts
Switchover Valves

I do not have your answer but do have a question. Where did you get your new switchover valves? I have a 1974 450SL that I am slowly replacing parts on.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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31,781 Posts
I will trace and verify tomorrow. In the meantime fill in your profile. Helps to know what vehicle we are discussing if it runs into more than one page as well as any resources in the area.
Do you have the manual or the CD?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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31,781 Posts
Another thought. Are you using the EPC? You are going to the dealer but you can save money by looking up your own part numbers and using the on line dealer sites.
 

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It Is What It Is, Dude
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22,839 Posts
.


BSHERMAN said:
Switchover valves: new versus old


Well, I'm no help to you there, but I just wanna ask the guy with the July '04 reg date, "Where the blue blazes ya been?".
 

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1972 350sl (4.5) 1987 M6 Euro 1995 840Cia 2012 E550
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42 Posts
Discussion Starter #8 (Edited)
EPC almost daily. Dealer for the parts I must (I just call in the numbers)....internet for everything else. After stripping the car to the metal, l I have rebuilt the entire suspension, subframes, brakes, firewall, AC system, and the electrical system....frankly I have rebuilt this entire car and know it quite well. I have collecting "goodies" from around the world for this car...my opus. I lived in Germany so acquisition of parts from "Der Vaterland" has made progress a bit easier. I have hard copies of the factory manual as well as the CD. Had my secretary create a hard copy of the entire EPC catalog to allow reference in the garage (3 inch binder!!), and have read the entire catalog twice! (no shitting!). I think I have a solution to my question but I need others with experience to chime in as NO WHERE are the difference in these switches been discussed (I've used the search engines...I already checked). Both my mechanic and the service manager at my local MB have an opinion...but they are in conflict.
As I finish this 8 year project, problems between the parts that exist and the original parts become more apparent...and I have overcome many problems. So I will now begin to use the forum for more of my problems. The car is a 1972 final vin 002781. I have a number of final questions to guide my final reconstruction. I've been checking and closely reading this forum for 6 years.....very, very helpful. I have significant experience on other boards with other cars I have rebuilt. So now I need to bring in others to help me get this car together.

For now, I want to confirm that the vacuum reconstruction is correct.
Hope this gives you a better feel for what this project is really about!
Regards
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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31,781 Posts
I misread the original question. Going out and looking at the old valves and hose routing would not help you. Sorry about that.
 

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1973 450 SL
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1,126 Posts
Is there a reason why your replacing those switchover valves? They last an eternity.

If it's cosmetic you may want to look at what I have done to mine. If yours are shot and need replacement then providing you with images won't help.
 

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1972 350sl (4.5) 1987 M6 Euro 1995 840Cia 2012 E550
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42 Posts
Discussion Starter #11
What did you do? The old metal brightens up on these cars with polishing but not to new state.

With a complete rebuild of this car, I chose to replace or rebuild every system. Sometimes that meant inspection and cleaning (cosmetics), and sometimes outright replacement. In general all rubber in the machine was shot. The plastic has aged very well. I could not get a good feel for the robustness of the valves, so I replaced them. This is likely an expensive "overkill" approach, but is yielding what is essentially a new car. Other than the body and the engine block, everything has been rebuilt or replaced. Any part with a potential for wear (mechanicals, valves...) was replaced. Only other exceptions were the diff and the steering box. Both checked to be very tight and the diff seals and drain bolts were replaced.

So, yes, these switch valves I merely replaced (sorry for the convoluted answer; but I sense the meaning of your question--why replace?)
 

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1973 450 SL
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1,126 Posts
I wanted to maintain originality as much as possible so, in the case of the switchover valves, I used eastwoods cadmium paint kit. These units cannot be re-plated due to the electronics so that is the route that I chose rather than install something that didn't even exist at the time of build.

Here are some photos of the engine bay in my car from which you can get an idea as to how well the cad paint worked. Not perfect, but in my opinion far better than replacement.

Sorry, but I don't have a photo of the valve behind the reservoir.

I also did the Exhaust Manifolds, header pipes and cross over pipe in polished aluminum ceramic coating. Looks a whole lot better than rusted cast metal and keeps the heat a bit lower in the engine compartment.
 

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1972 350sl (4.5) 1987 M6 Euro 1995 840Cia 2012 E550
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42 Posts
Discussion Starter #13
Wow! Very, very nice work. I know what it takes to make that car look so wonderful, especially the intake manifold! New harness...nice! Alternator bracket and supports! I have collected hundreds of pics of early 107 engine bays in preparing for my project...yours is by far the nicest.

I have the three spray cad system you speak of, and have used it on the car in areas I did not want to spend $ on (i.e.: the carrier for the fuel pump assembly). I know it well. I agree this would be the ideal place for the system (that red and green are bit hard to use, though!).

I know how to post pics on Roadfly...I'll figure it out and post some progress pics here.

Still waiting advice on the valve. Since the new valve toggles between ports 1 to 3 when closed (de-energized) and port 2 to port 3 when open (energized), and if you analyze the native set-up with the original valves in place, the MOST reasonable assumption is that the common port (3) corresponds to the bottom center port, the de-energized or open port (1) is the top port; and the energized port (2) is the bottom lateral port. This would allow the right valve to suck the water valve diaphragm when energized while simultaneously the left valve would vent the opposite chamber of the water valve when energized. Just the logic. Any comment?
 

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1972 350sl (4.5) 1987 M6 Euro 1995 840Cia 2012 E550
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42 Posts
Discussion Starter #14
After mapping out the control functions of the valves, it is clear I have them reversed.

The common port is the lateral port on the new and old valves (position 3 on the new vlaves, or the bottom edge port on the old ones.). Position 2 on the new ones (top) is the bottom center port on the old ones. Position 1 (bottom of new ones) is the top center of the old ones. This allows the suction to reverse when activated and the vent to be simultaneously reversed when activated without loosing the vacuum to the vented ports. I have the bottom ports reversed in the description above. If you draw it out it makes sense. The MB tech was correct. My mechanic (former MB foreman, BTW) had it reversed (as I did). Done!
 
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