mystery tube on front of engine ???

[blairwag]

I have an unidentified tube on the front of my engine. It's of concern because it is dripping motor oil, I *THINK*.

This tube appears to be made of plastic. It's mounted to the front of the engine block just barely behind the upper driver side of the crankshaft pulley / balancer (that big round thing in the lower front of the engine, with the timing marks on it). It is just slightly below the driver side of the water pump.

This tube is mounted with a round brake line like fitting, with a hollow bolt the goes through the center of it (connecting it to the block).

The tube extends upward towards the distributor. It is fastened to the block by a little retainer just behind where the distributor enters the block. The tube then heads away from the engine, towards the driver side fender. It passes right in front of the big black cynindrical filter housing looking thing with the wing nut on top (what is that, an air filter?) and points toward the battery. There it is broken off - with no clue as to where it should go.

What is this tube? Where *SHOULD* it lead? What should I do with it? Is it possible it's spewing oil into my engine compartment?  The whole side of the engine and accessories on the driver side are all wet with oil. I suspect this is the source.

Any advise/help would be totally awesome! TIA :-)


--
~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Blair Wagner: blairwag@earthlink.net
Education is not always knowing the answer,
...but rather knowing where to look for it!
~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Tom]

William,

You did not specify the year of your car but I am assuming it is a later model that vents the fuel vapor from the gas tank/black vapor box in the trunk of the car to the crankcase-sort of a recirculation to keep the vapor from venting to the atmoshphere.  Earlier versions vented to the atmosphere.  I am not sure if this impacts performance or not but I have found that, *generally*,  it is best to get each of the mechanical elements back to original design/function to ensure the car runs at it's best.

Best,

Tom

[blairwag]

Yea, the year / model might be useful information.
The car is a MB 1971 280 SL US delivery, with 4 speed automatic transmission, and frigiking A/C.

I'd love to know for sure what this tube is for, and what to do with it (repair?). If it is spewing oil, I'd *REALLY* like to fix it, and clean the engine up a bit.


--
~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Blair Wagner: blairwag@earthlink.net
Education is not always knowing the answer,
...but rather knowing where to look for it!
~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Tom]

William,

Now that you verified that your car is a late model US spec car, I am sure this is the vent line that takes fuel vapor into the crankcase.  You should find a 2nd open end of a tube that is open near where the kickdown switch emerges at the bottom of the car.  The line is grouped with 2 or three other lines that are metal (brake and fuel lines I think).  You will need to get some additional lengths of the black plastic line and connect it to each of the open ends with a small black rubber vacuum type line.

The cansister you refer to with the wing nut is the power steering reservoir.

Best,

Tom

[blairwag]

Can you give me a little more detail? Where is this "kick down plate"? Not knowing where the other end of this tube is, and not knowing how much of it is broken/removed, can you give me an indication of where this tube/line runs?  Does it go all the way back to the fuel tank? Where does it run? I've looked all around the engine compartment and I can't find another open myster tube that this one might belong to. Where should I look?

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Blair Wagner: blairwag@earthlink.net
Education is not always knowing the answer,
...but rather knowing where to look for it!
~~~~~~~~~~~~~~~~~~~~~~~~~~~

[rwmastel]

William,

Assuming Tom is right (he is a very bright guy!), this tube would run from the fuel tank to the front of the car because, as Tom said, it returns fuel vapor to the engine.  I'm not sure of it's exact path because my car is too old to have one, but it probably runs under the driver's side floor.  Look for the other fuel and brake lines.  The kickdown switch is the switch under your gas pedal that forces the automatic transmission to down shift when you floor it.  Looking at that area from under the car, you should be able to find the lines in question.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[n/a]

William

I think the line you are looking at is an oil line that runs from the engine side of the fuel injection pump to the front left side of the engine block.  It is about 1/8th inch in diameter and made of copper or light gage steel.  The fitting you described on the engine block is a "banjo" fitting.  My 65 230SL has a fuel injection pump oil return only.  My understanding is that later cars had pressure feed (to the fuel injection pump) and a return line.  Joe Alexander has written quite a bit about these pumps and posted some great images.  Try searching the archives for "Injection Pump" or posts by Joe Alexander and I'll bet you'll come across images of the line you are describing.

Good luck and happy new year

TonyM

quote:Originally posted by blairwag

I have an unidentified tube on the front of my engine. It's of concern because it is dripping motor oil, I *THINK*.

This tube appears to be made of plastic. It's mounted to the front of the engine block just barely behind the upper driver side of the crankshaft pulley / balancer (that big round thing in the lower front of the engine, with the timing marks on it). It is just slightly below the driver side of the water pump.

This tube is mounted with a round brake line like fitting, with a hollow bolt the goes through the center of it (connecting it to the block).

The tube extends upward towards the distributor. It is fastened to the block by a little retainer just behind where the distributor enters the block. The tube then heads away from the engine, towards the driver side fender. It passes right in front of the big black cynindrical filter housing looking thing with the wing nut on top (what is that, an air filter?) and points toward the battery. There it is broken off - with no clue as to where it should go.

What is this tube? Where *SHOULD* it lead? What should I do with it? Is it possible it's spewing oil into my engine compartment?  The whole side of the engine and accessories on the driver side are all wet with oil. I suspect this is the source.

Any advise/help would be totally awesome! TIA :-)


--
~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Blair Wagner: blairwag@earthlink.net
Education is not always knowing the answer,
...but rather knowing where to look for it!
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Tony M
1965 230SL (Auto)

[Cees Klumper]

Tony - this is the first thing I thought of, but I think Tom is right, identifying it as part of the emissions controls plumbing. It would help to see a photo. I would guess that if it were the oil line to the FI pump, and it is undone or broken, it could leak a LOT of oil.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[ja17]

Hello William,
Tom is correct on this matter. The tube is a vent which returns fuel vapors
to the engine on USA cars during this era. This keeps fuel vapors from
escaping into the air. Earlier engines had no hole in the engine fitting or plastic
return line.
The return line on your car is not unique to injected engines, but also used
on the USA Mercedes carbureted engines of that era.
This line should run along the left side of the engine compartment and
follow the fuel lines to the  rear of the car. Look under the car on the
driver's side and see if the remnants of the plastic vapor line is still in
place running with the fuel lines.
The other metal line which Tony is referring to is the oil lubrication line for the injection pump which runs from the side of the block to the injection pump.


Joe Alexander
Blacklick, Ohio

[blairwag]

Sure enough, with the help from Tom Sargeant *AND* Joe Alexander, I've identified the mystery tube as the crank case to fuel tank vapor return line. I've located the other side of it. Sheeewwww! I was worried about the possibility of the line being an oil feed to the fuel injection pump. If that was severed, wouldn't that damage the punp in short time?

The tube appears to have been broken and repaired in the past. The repair gave away. I'm sure, using rubber tubing, I can splice the ends back together.

However, since this line broke, I seem to have oil dripping out of it while running. If I repair the tube, won't this nasty oil end up in my fuel tank?  Is this normal?  Is this a symptom of another problem, do you think?

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Blair Wagner: blairwag@earthlink.net
Education is not always knowing the answer,
...but rather knowing where to look for it!
~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Tom]

William,

I guess that oil is escaping from the tube as it connects to the crankcase and pressure from the crankcase is pushing oil out of the tube.  If the tube is reconnected, it seems that positive vapor pressure from the fuel tank will keep the flow toward the crankcase.  There is a check valve in the trunk that should keep oil from making its way back to the gas tank.

Rubber tubing is what the factory used to allow for the various bends that the tube must make to get to the crankcase-adding a few more connections, while not perfect, should be ok.

Best,

Tom

____________________________________

1971 280sl Tunis Beige Metallic
1971 280sl Tobacco Brown
1994 E320 Cabriolet, Smoke Silver
1999 E320 Wagon 4 matic, Brilliant Silver
____________________________________

[ja17]

Thanks Tom,
I corrected my previous post. As Tom described, fuel vapor is vented to the engine from the tank via the plastic line.
I think the early W113 cars had a vented gas cap. Later W113 cars with the plastic vent line did used a sealed gas cap.

Joe Alexander
Blacklick, Ohio