Smoke coming out of valve cover vent hole on 300SDL - PeachParts Mercedes-Benz Forum

ah-kay · #1 04-22-2010, 10:57 PM

I noticed smoke coming out of this vent hole when the SDL is mis-firing at idle. What can cause smoke to come out? Would it affect idling? Something wrong with the engine? At other times the engine runs very smoothly. Something plugged?

Any input is appreciated.

pawoSD · #2 04-22-2010, 11:15 PM

Plugged vent line or excessive blowby pressure would be my guess.

ah-kay · #3 05-12-2010, 03:40 PM

The engine is missing at idle when smoke is coming out form the vent hole. Other times it is purring like a cat and smooth idling. This project car has 332K miles. What is the problem? Too much blow by? I removed the oil cap and smoke comes out and oil splattering. However, it starts right up with 1 spin and drives well.

What shall I do next? Try adding some Marvel Mystery Oil and soak it for a while? Any idea is welcome.

Diesel911 · #4 05-12-2010, 08:08 PM

I do not know if this is related or not. While my Engine was hot and idling I put my thumb over the Breather Tube that gotes tot he Air Filter.
With it completely blocked in about 7 seconds my Engine started to stumbel and try to shut down. When I removed my Thumb the Engine returned to normal.
(By the way I was told that the above is not a good thing to do as it puts pressure on the Engine Seals; so use your best judgement if you try it.)

So I am guessing that if enough pressure build up it effects the idle.

I am speculating that the pressure is building up and you start to miss and smoke comes out of that vent.
When the pressure reaches a certain point it is relieveing itself some where on/in your Engine and then ounce relieved it takes a while for the pressure to build up again. During that time the smoke at the vent hole stops and your Engine runs OK.

It might be interesting to pull the Breather Tube off of the Air Filter and see what is coming out of it and see if it changes anything. Could be your Breather system needs cleaning.

More sepeculation.
If it is really smoke and not Oil Vapor may be there is something going on with an Exhaust Valve that is seating intermittantly during the Power Stroke and hot expanding combustion gas is getting past the valve and coming out of the Stem Seal and at the same time the poor compression is is causing a miss.

See if you can locate a specific Cylinder as the cause of the miss by doing the Injector Cut Out test.

layback40 · #5 05-12-2010, 08:29 PM

Isnt that little hole for a screw that holds a bracket in place? I would put a small bolt/screw in it to block it off. I dont believe its meant to breath out that hole. Some one please correct me if I am wrong. Neither of my 617's have a breather there.

vstech · #6 05-12-2010, 09:15 PM

Quote:

Originally Posted by Diesel911

I do not know if this is related or not. While my Engine was hot and idling I put my thumb over the Breather Tube that gotes tot he Air Filter.
With it completely blocked in about 7 seconds my Engine started to stumbel and try to shut down. When I removed my Thumb the Engine returned to normal.
(By the way I was told that the above is not a good thing to do as it puts pressure on the Engine Seals; so use your best judgement if you try it.)

So I am guessing that if enough pressure build up it effects the idle.

I am speculating that the pressure is building up and you start to miss and smoke comes out of that vent.
When the pressure reaches a certain point it is relieveing itself some where on/in your Engine and then ounce relieved it takes a while for the pressure to build up again. During that time the smoke at the vent hole stops and your Engine runs OK.

It might be interesting to pull the Breather Tube off of the Air Filter and see what is coming out of it and see if it changes anything. Could be your Breather system needs cleaning.

More sepeculation.
If it is really smoke and not Oil Vapor may be there is something going on with an Exhaust Valve that is seating intermittantly during the Power Stroke and hot expanding combustion gas is getting past the valve and coming out of the Stem Seal and at the same time the poor compression is is causing a miss.

See if you can locate a specific Cylinder as the cause of the miss by doing the Injector Cut Out test.

your car stumbles because the vent gasses push against the fuel shutoff diaphragm. it is indeed a bad thing to do this.

Diesel911 · #7 05-13-2010, 10:56 AM

Quote:

Originally Posted by vstech

your car stumbles because the vent gasses push against the fuel shutoff diaphragm. it is indeed a bad thing to do this.

It makes sense if the other side of the Shutoff is exposed to the Crankcase Pressure, thanks for the info; I had not thought of that!

compress ignite · #8 05-13-2010, 01:07 PM

Layback40,

All EGR equipped (And electro/vacuum actuated throttle equipped) engines
have the 1mm vent.
It MUST remain un-obstructed.

Uggrrrkkkkk! EDIT:

I have no idea if the 1mm valve cover vent is Vacuum or Pressure (???)
The Urdu instructions speak of dangers of Oil Sump being emptied by Vacuum
BUT CALL the 1mm vent "Pressure" in the Pictogram's legend.

[Section 01-040 crankcase ventilation ]
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/01-040.pdf

Normally ,on the Turbo-ed Om 60(2,3).XXX engines the Breather hose from the top
of the Valve cover to the Turbo intake hose has Suction on it and Takes care
of any errant gasses in the Valve cover.

In this case,"ZomeZing" is wrong with the Vent's oil separation function
(SEE all the oily mess underneath it on the Valve Cover side?).
AND I suspect the Vent hose from top of Valve Cover to Turbo intake is Occluded Also.
If (as I now interpret the Engineer's Scribe's instructions) the 1mm Vent is
working ...Having Oily Mist "Blow Out" it's Orifice,indicates two possibilities
1.Too much pressure inside the Valve Cover
(Overcoming the natural vacuum which should present with the intake sucking on the Valve Cover to intake vent hose.)
( Maybe the Vent Hose is occluded?)(or the 90 degree Plastico fitting?)
2.laws of Physical Universe suspended inside this particular valve cover's
1mm Vent apparatus.

ah-kay · #9 05-13-2010, 04:47 PM

Quote:

Originally Posted by compress ignite

Layback40,

The Vent Opening in side of Valve cover is an OM 602,OM 603 "Thang".
It MUST remain un-obstructed.It's the last ditch defense for engine seals.

Normally ,on the Turbo-ed Om 60X.XXX engines the Breather hose from the top
of the Valve cover to the Turbo intake hose has Suction on it and Takes care
of any errant gasses in the Valve cover.

In this case,"ZomeZing" is wrong with the Vent's oil separation function(SEE all
the oily mess underneath it?).AND I suspect the Vent hose from top of Valve
Cover to Turbo intake is Occluded Also.

Where shall I check for blockages? Need some pointers here.

Thanks

Crazy_Nate · #10 05-13-2010, 06:49 PM

Where's the PDF from?

The hole on your valve cover is not in the same location. Different engine revision / documentation?

ah-kay · #11 05-13-2010, 09:14 PM

Quote:

Originally Posted by Crazy_Nate

Where's the PDF from?

The hole on your valve cover is not in the same location. Different engine revision / documentation?

The PDF file is a link I found in this forum to illustrate the vent hole. The actual engine is a 603 as shown in the picture. Vent hole is on the left rear of the valve cover.

layback40 · #12 05-14-2010, 07:31 AM

Thanks compress , Its great to learn some thing new. I dont think my NA 602 has that hole. I cant find it.

04 Diesel · #13 05-14-2010, 07:54 AM

My 602 has the same hole.

compress ignite · #14 05-14-2010, 08:04 AM

So Damn small you might miss it.
When you take the Valve Cover off and turn it upside down,you'll see a cover
plate over the Baffle apparatus that is supposed to prevent the Vaporized Oil
discharge. 'You're seeing from the 1mm vent hole.

[So much fun wrapping your head around the Ulan Bator translation of Navaho
interpretation of Instructions dictated by the Engineers in German to scribes
who only speak Urdu.]
I have no idea if the 1mm vent is actually a Vacuum vent or Pressure. it's
function is to prevent the "Zomezing" from sucking the Sump Dry.
[Now corrected in earlier reply]

Section 01-040 crankcase ventilation (Pictograms below):
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/01-040.pdf

2.The Rubber Vent hose from the Valve cover to the Intake[upstream of the Turbo] must be clean and able to pass the "Blowby" from Valve cover to Intake.
(And the 90 degree plastico fitting on top of the Valve Cover)
(The 90 degree fitting will usually be "Heat Hardened" and a Witch to R+R
without "Pranging" it...Careful)

compress ignite · #15 05-14-2010, 09:10 AM

Layback40,

If I'm reading the Urdu correctly the 1mm vent will be in all EGR equipped engine
valve covers.(Which have the Damn Electro/Vacuum operated "Throttle" in
the Intake between the air cleaner and the Crossover Pipe.)

Ah-Kay,

The oil separation apparatus (And spring powered vent)
inside the underside of the Valve cover is not "Dis-Assemble" enabled.
(I just went out and pulled the Valve cover off the Exemplar 602.)
There is a very thin Aluminum Plate sort of "Riveted" onto the Vent Chamber.
(Small Aluminum posts "Peened" over on the Aluminum Plate to secure it
to the Vent Chamber.)
You might be able to GENTLY drill out the "Peened" heads for access.
(Or use a set of "Side Cutters" on them)...No Idea how to re-secure,Yet.

I'd be tempted to turn the Valve cover upside down and fill the Vent Chamber
with some sort of GENTLE solvent...Let it soak a coupla days ...
Then drain and blow dry.
The Concern AGAIN is for the Vent Diaphragm...If it's Non-Viton
Rubber it'll be in danger with a strong Bio-Diesel or Solvent Soak.

If as I suspect the Diaphragm is Rubber,I'd want to be careful about what kind of cleaning agents used.