Smoke coming out of valve cover vent hole on 300SDL - Page 2 - PeachParts Mercedes-Benz Forum

ah-kay · #16 05-14-2010, 01:49 PM

I think the engine is buring motor oil near where the turbo is when the engine is missing and smoke coming out of the little vent pipe. The exhaust smell is horrible. There is some black smoke but not a lot unless I rev the engine.

What is inside the big rubber accordian tube that the valve cover vent goes into? I suspect something inside is burning oil and is passed to the exhaust, increase the pressure ( not sucking the blowby ) hence smoke coming out from the small vent hole.

Anything I should check near the turbo?

compress ignite · #17 05-14-2010, 02:07 PM

The large diameter hose that feeds the TurboCharger is the Intake from the
Air Cleaner Housing.(It has the smaller diameter Valve Cover Vent hose running
into it in a "T" Upstream of the Turbocharger.)The Turbocharger when the engine
has any RPMs on it produces LARGE Suction on BOTH those hoses.

The Oily Mist and Crankcase/Valvetrain PRESSURE being Vented out the Little
1mm orifice on the side of the Valve cover is PROOF of Excess "Blowby".
Something is putting SO MUCH PRESSURE inside the Valve cover (or the top-
of -Valve Cover Vent hose system is Block[ing]ed) that it's OVERCOMING the
Turbocharger's SUCTION.
('Called a MB Shop Foreman and described your symptoms to him.)

Since you're only experiencing the "Venting" along with rough running the excess Pressure MAY be attributable to Valve Stem Seal problems.
Or some
problem with the Valve Train which is allowing the Cylinder Pressure direct
access to the Valve Cover.If it's on the Exhaust Valve side the incomplete
combustion would lend itself to the "Stinky Exhaust".I'm going out on a limb
and Prognosticate it's an Intake Valve Problem...Bad Seal...It sucks in Oil
from the Valve Cover Lube System...Incomplete Combustion and Oily Exhaust.
OR it may be Both at the same time.

Hell, it could be one or more bad rings.
You need more Diagnostic Info.

Try the "Loosen the capnuts (One at a Time) on top of the injectors trick"
to try and narrow down WHICH cylinder's Valve Stem Seal(or Whatever) is bad.

I'm almost sure a Cylinder Leak Down Test will tell you everything you want
to know.

Oh Yeah,your only Easy Fix option is if the Top of Valve Cover Vent Line
(that runs from the 90 degree plastico fixture in the top of the Valve Cover
to the accordian Tube feeding the Turbocharger) is stopped up.So Check it,FIRST!

compress ignite · #18 05-14-2010, 02:26 PM

No Way this is one of the 3.5 "Rod Benders" is there?

ah-kay · #19 05-14-2010, 02:34 PM

Quote:

Originally Posted by compress ignite

and Prognosticate it's an Intake Valve Problem...Bad Seal...It sucks in Oil
from the Valve Cover Lube System...Incomplete Combustion and Oily Exhaust.
OR it may be Both at the same time.

Hell, it could be one or more bad rings.
You need more Diagnostic Info.

Try the "Loosen the capnuts (One at a Time) on top of the injectors trick"
to try and narrow down WHICH cylinder's Valve Stem Seal(or Whatever) is bad.

I'm almost sure a Cylinder Leak Down Test will tell you everything you want
to know.

Oh Yeah,your only Easy Fix option is if the Top of Valve Cover Vent Line
(that runs from the 90 degree plastico fixture in the top of the Valve Cover
to the accordian Tube feeding the Turbocharger) is stopped up.So Check it,FIRST!

I am no good with engine as I am not that mechanically inclined.

1) I suspect it may be valve issue as I hear metallic tapping sound, sometimes. I will remove the valve cover and take a look.
2) The car has 332K but it always start first time. So there may be blowby but compression should be reasonable.
3) How to perform a 'Cylinder Leak Down'? Any special tool I need?
4) The vent hose is not block as I removed it from the rubber accordian hose and I saw smoke coming out. If I block it then the dip stick pops out and motor oil splashed everywhere. What does it tell us?

ah-kay · #20 05-14-2010, 06:00 PM

Compress-Ignaite: Thanks for the info.

It is a 3.0L, not a 3.5L rod bender. I read up the 'Leak Down Test' on the Internet and will try to do it this w/e or next. I thnk your are right that the test will give me a lot of info.

compress ignite · #21 05-14-2010, 07:49 PM

It's a Super Duper compression type test.
'Uses two gauges to compare how quickly compressed air escapes the Cylinders.
(You'd need an Air Compressor) and the test kit. [example from the H.F. site]
It's a fairly involved (But,step by Step) procedure.

I would not even take the Valve cover off, yet.

The Blow By pressure "Launching" the dipstick (It's got at least one rubber o-ring,securing it in the dipstick tube...Age and Pliability unknown) pretty
much confirms the Shop Foreman's telephonic diagnosis of Too Much Blow By.

You might get lucky and only have a Hydraulic Lifter "Hanging Up" on you.
They are little round hydraulic devices that are in between the valve stems
and the Camshaft that are operated by Oil Pressure.(They take up the slack)
If one (or More) were staying filled it/they might prevent the valve(s) from
closing all the way.The "Fix" (other than replacing) is to run Synthetic Oil
which seems in a lot of cases to clean out the tiny little bores.

The metallic tapping COULD be a lifter.(Of course it could be an Injector)

You now know what the problem is...Just not what's causing it.

AND you've no empirical evidence that the compression is "Good" (within specs) without a compression test.The excess "Blow By" could be caused
by pressure slipping by worn or damaged rings.

compress ignite · #22 05-14-2010, 08:06 PM

"Stumbles" engine.

(Looking for my 5th lesson of the day)

vstech,

Please detail for me the path the pressure takes from the crankcase/valve system to the inside of the Injection Pump ,to sneak in behind/underneath
the Vacuum shutoff valve diaphragm (And semi-operate the fuel shut off
rod)

Thanks!

ah-kay · #23 05-14-2010, 08:43 PM

Quote:

Originally Posted by compress ignite

I would not even take the Valve cover off, yet.

How do I know the valves are at TDC if I do not take the valve cover off?

ak49er · #24 05-14-2010, 10:42 PM

My .02....adjust your valves.

I say this as I have a 1983 300SD, TurboDiesel that had 51,000 miles by two owners. I put another 28,000 on, mostly on WVO, on the highway. And noticed that the breather tube and intake area was becoming dirty with oil, and I could see it puff smoke out of the oil filler cap. I bit the bullet, adjusted my valves, and no more puff of smoke out of the filler, and the intake tract (form valve cover to inside of air filter, is now clean and oil free.

Now with in-spec. valves , the difference is definitely noticable in runablilty and performance.

There is a detailed explanation on how to properly perform the "Blow-By Test" on the www.frybrid.com website. It explains the htoery, precatuions and what to decipher from the test. It is risky, but when done properly, can give needed answers.

Good Luck.

vstech · #25 05-14-2010, 11:08 PM

602/3/6 etc, have hydrolic lifters. nothing to adjust.

vstech · #26 05-14-2010, 11:11 PM

Quote:

Originally Posted by compress ignite

"Stumbles" engine.

(Looking for my 5th lesson of the day)

vstech,

Please detail for me the path the pressure takes from the crankcase/valve system to the inside of the Injection Pump ,to sneak in behind/underneath
the Vacuum shutoff valve diaphragm (And semi-operate the fuel shut off
rod)

Thanks!

um, isn't the IP connected to the crankcase? I know it is oiled by the motor oil, and it's gotta drain somehow...

compress ignite · #27 05-15-2010, 12:02 AM

vstech.

I Think (?) the I.P. drains through the Timing Device.

Ah-Kay,

Correct.

O.K. IF, you're going ahead with Leak Down Test.
You'll need the V.C. Off to be able to see each valves camshaft lobe.

Read everything in the procedures three times , and do not allow yourself to be distracted.

ah-kay · #28 05-21-2010, 01:57 AM

Removed the valve cover ( with great difficulties ) with the intention to do a Leak Down Test. Everything under the valve cover look normal to my untrained eyes. The vent hole is connected to a hook shape tube. I think the tube is normally filled with engine oil which blocks any smoke from coming out. When the pressure is too high then smoke will blow pass the tube and vent through the small hole. This is what I think happens.

I bought the Leak Down Tester from HF but did not realize that I need an adaptor to plug into the injector opening. So I put everything back together for now. Went out for a spin and the car ran perfectly and purred like a cat, no smoke from vent hole. Cleaned up the garage and started the car again to put it back in then the car is missing at idle. Smoke coming from the vent hole. I then loosen the nut on top of the injector one at a time try to isolate a cylinder but smoke did not stop with any one nut.

What does it tell me? All 6 cylinders have bad blowby (331K on car)? Can blowby come and go suddenly? BTW: where can I get a adaptor for the Leak Down Tester? Can I make one?

Thanks in advance.

skelleybenzes · #29 05-25-2010, 09:33 AM

Ah-kay,

I'm experiencing the same issues (perhaps more severe) as you, and have been posting to the thread "OM603 Idles, Won't Pick Up Speed." Just found the excessive crankcase pressure last night, and will follow the thread here to see your progress--you may want to follow mine from today forward if it would help. Good luck!

ah-kay · #30 05-25-2010, 12:14 PM

Quote:

Originally Posted by skelleybenzes

Ah-kay,

I'm experiencing the same issues (perhaps more severe) as you, and have been posting to the thread "OM603 Idles, Won't Pick Up Speed." Just found the excessive crankcase pressure last night, and will follow the thread here to see your progress--you may want to follow mine from today forward if it would help. Good luck!

I will follow yours post with interest. The car's blowby seems come and go. When it does not happen it purrs like a cat and drives really well. When it happens it just misses in idle but if in drive then it also drives very well. I am 'waiting' to do a leak down test. I am in no hurry as it is drivable as it is. I suspect it may the the hydraulic lifter but I am not sure.

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