Early (230/250/280SL) fuel evaporation tank

[66andBlue]

While we have nice diagrams in the technical manual explaining how the evaporation tank on the later 280SL cars work there is nothing about the earlier tank.
Can someone explain to me please how the early tank works?
Also, would be nice to see where the two lines originate inside the tank. Who can post a photo?

It is also noteworthy that the tanks between the 230SL and early 280SL are slightly different resulting in a different pipe order. On the 230SL the pipe going to the outside is in the rear while on the 280SL it is on the front.

[Pawel66]

Alfred,

I am not sure what is missing in the Technical Manual regarding the earlier tanks - seems there is quite a lot there...

Maybe we can add:
- the tank is a very simple device, just with chambers inside that just overflow, no valves are there (I saw a drawing somewhere, I will check Haynes)
- it is not designed to be dismantled to be cleaned; never tried it, but if you cut it to e.g. clean it, you would have to glue it together
- the size and shape of clips holding it to the trunk side panel changed over years (thickness of studs on the tank, clips shape, shape of cut outs in the panel); need to watch what you buy
- the cone is designed with high level phisics  (its shape creates some vacuum)

At least part of the answer you are asking is also in the Tech Manual (a bit of synthesis needed, as for most of modern science) - I attached the picture. The other vent line is, I suppose, the return, so it does not have to be long and lead anywhere.

[Pawel66]

Just maybe to complement the post: I see you have the picture of the early one. The cone connector is the one outside, first to the right if you look at the tank as on your picture. In the later one it is also the one outside, the back of the car (not SLS, but EPC has it a bit wrong, sorry, I wrote it wrong).

I am attaching SLS picture (you have to turn around the tanks on this picture to have it as they are in the car on the right of the trunk).

I am also attaching the picture of the newer tank - the one in which connectors break all the time.

I think in general: the thickest line, a bit aside from the rest, is the line to cone. Then next to it is, I think the line to the nipple outside of the filler neck (I think, not sure).

I also think that  is does not matter which line goes to which nipple as fuels goes up and down in both all the time. The cone one is important.

[Pawel66]

One more picture: this is the EPC picture. It suggests the tank has connectors on its left hand side.

I have never seen this type of tank, but the connections here are fairly straightforward, I think: far left is the cone, the next one is the more outside nipple in the tank.

[66andBlue]

Alfred,
I am not sure what is missing in the Technical Manual regarding the earlier tanks - seems there is quite a lot there...
At least part of the answer you are asking is also in the Tech Manual (a bit of synthesis needed, as for most of modern science) - I attached the picture. The other vent line is, I suppose, the return, so it does not have to be long and lead anywhere.

Pawel,
I was not questioning the information on the fuel tanks but the lack of information about the EARLY expansion tanks.
I was looking at this page:
https://www.sl113.org/wiki/Fuel/VaporTank
and as you can read there is nothing about the earlier evaporation tank.
Unfortunately,  until today I missed the page that paladin added: https://www.sl113.org/wiki/Fuel/VentingSystem
I am glad I found it since I was unaware that the vent line is thicker (6mm) than the other two. Makes it easy to distinguish them.
I guess time has come to combine the two entries in the manual.

I still want to see where the vent pipes are in the small (230SL) and the large (280SL) tank.
Reason being that the 1968 BBB describes a tank (from a different model, not a W113) where the lines are connected to the filler neck (Fig. 47-2/2). That makes a lot of sense - if you fill the neck and you have an un-vented gas cap then the excess fuel goes up the two pipes into the expansion tank. Especially on acceleration or steep hills.
It appears you believe that one vent line goes all the way to the front of the tank. If that is the case then every time you brake or go downhill that line would get filled and fuel would circulate causing increased evaporation (higher fuel consumption) over time.
Are you absolutely sure that inside the expansion tank there are no valves, perhaps just a ball, that close the vent lines?  The fuel tank is always open to the outside via these lines??

Unfortunately,with the switch to the larger tank all the part numbers for the vent pipes and hoses were eliminated. Looking at the SPL for the 280SL it now appears as if the expansion tank came with three vent lines already attached to the tank since there are no longer any entries for the metal pipes - just like the SLS picture shows it.
Now that cannot be correct because we know that some 280SL - mine, paladin's and mrfatboy's - have metal pipes.
When were the metal pipes in the 280SL eliminated??
Lots of uncertainties here, I say.

[Pawel66]

Alfred,

Yes, the info on early expansion tank was in a different place... And the picture of nipples connection inside the tank - also somewhere else.

I was not analysing in detail the enclosed evaporation system, I just took the general idea from it about the "high chamber" in the expansion tank being the one for vapours and leading down to cone. And this makes sense. The nipples being at the filler neck or somewhere else - does not matter - if you fill up too much, fuel will spill through filler. If you accelerate the fuel will go to the back, if you brake the fuel goes to the front. In most of our cars (open evaporation system) one nipple takes fuel from the front (as on the picture I posted above) and the other from the back. The fuel flows back and forth through both lines to and from the expansion tank.

Yes, I am certain the "high chamber" is for vapours. This is logical. And yes, I am certain there is nothing but chambers inside the "regular" expansion tank. I have read it in several places. I think mdsalemi was writing he had cut open one of these tanks and "there was absolutely nothing inside". If you connect cone line to one of the nipple lines connectors - you will get fuel that flows in from the tank to the chamber directly going down to cone. So the cone line is specifically distinguished by being thicker.

On some tanks (mrfatboy's) you can determine that, as you see how the tank is build, you see the "high chamber".

My car is March 1970 280SL and it also has the brass pipes, not the expansion tank with plastic lines coming out. I do not know if this was the original set up or if someone fixed it - as we know these plastic lines usually break away and the only way to repair it is to fit the brass pipes. In my country the common fix is to use one of the standard metal ballpen refills as they fit nicely. In the EPC we do not have the chassis number as of which the expansion tank with fittings was replaced with the one with plastic lines (like on the picture I posted above, from e-bay). But even if you make the EPC search for 113042 parts - it shows the picture with  lines attached to the tank and it does not even show the steel lines nor the hoses between steel lines and tank. It is not the first time when something was just changed without major updates if it did not trigger a lot of changes in other places (like the throttle axle cover for instance  ).

i was going through all that 3-4 years ago as my Madame did not like the fuel smell. I had to re-build the whole arrangement and I had no smell ever since (other than a bad sender gasket in the meantime, but this is another story).

[66andBlue]

Pawel,
as usual your memory hasn't failed you. 👏👏

I found a photo that Detlef Hahn posted on his web site showing the open tank and indeed there is no indication of any check valves.

As to the entry in the 250/280SL spare parts (10142 and 10202) it is very likely that MB screwed up. The pictured tank with the attached three lines (like the current replacement) was most likely never installed at the factory in a 113-043 and 113-044.
I have corrected my earlier post to prevent any confusion.

[Pawel66]

Alfred,

Thank you!. Now as you confirmed and added additional info - it is all really for sure.

I have an excellent memory, it is just short... 

I remember when I had trouble with this "system" I was looking for information what might have clogged inside this tank or if some valve got bound. Then I found it in a couple of places that it is just empty two chambers.

If I were replacing the tank and had nothing but the current replacement part, I would probably cut fittings and install those tiny pipes there to connect the existing hoses/lines combination, which is cool in its unnecessary (Mercedes typical) complication of using (1 tank, 2 clips, 1 cone, 6 hoses, 12 clamps (?), 2 brackets, 2 screws and washers and 3 steel lines) up to 31 parts instead of (1 tank, 2 clips, 1 cone, 3 hoses, 6 clamps (?), 2 brackets, screws and washers) 19 like in the latest solution - if my imagination of holding the plastic lines to trunk wall is correct.

[Shvegel]

As deceptivly simple as those early expansion talks were I bet there was an evolution to get to the final design.  It probably started with one line up to the tank then they figured out under hard acceleration it would overflow the tank so another line was added to the rear of the tank so under acceleration the fuel in the tank could drain back to the front of the tank.  Even the tanks size was probably an issue given that cool fuel sunjected to 120 degree F desert heat will expand quite a bit.