Turbo Diesel oil in intake manifold?

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Dave - 31 Aug 2003 03:27 GMT

I was changing the glow plug harness in my 1994 S350 (168k) and took
off the intake manifold to get at things. I think I found where the
blue exhaust smoke is coming from. The manifold is caked with thick
oil residue that looks like it has been there for years, but also has
a thinner layer on top that looks rather recent. I can trace it right
back to the turbo.
My guess is that there has always been a little bit of oil coming from
the thing, but now there is a lot. Looks like I'm down about a quart
in 1500 miles. Haven't noticed any oil loss before the last oil change
- at least not much (always leaks a bit here and there).

Are there any seals or gaskets or whatever in the turbo that can be
replaced?

What to do?

Thanks

-Dave Walton

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T.G. Lambach - 31 Aug 2003 06:43 GMT

The intake manifold will be caked with soot and oil. Soot from the EGR
system - normal - and a bit of oil from the crankcase ventilation system
aka as "the breather" - also normal.

I believe there's a vent hose from the top of the valve cover over to
the air cleaner or some point on the air passage to the turbo's air
inlet. There's always a bit of oil in the crankcase fumes and it is what
you see inside the intake manifold. Normal. Don't blame the turbo, they
rarely fail.

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T.G. Lambach - 31 Aug 2003 06:47 GMT

Are you aware of this 3.5 L diesel's reputation for bending its
connection rods?

Oil consumption - usually past the #1 and #4 pistons - is a symptom of
greater things to come. Owners of these engines have not been a happy
lot.

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Dave - 31 Aug 2003 17:06 GMT

I have come across references to this engine problem here and there,
but was unable to find anything that covered it in detail. Is this
fixable?

Thanks

-Dave Walton

> Are you aware of this 3.5 L diesel's reputation for bending its
> connection rods?
>
> Oil consumption - usually past the #1 and #4 pistons - is a symptom of
> greater things to come. Owners of these engines have not been a happy
> lot.

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T.G. Lambach - 31 Aug 2003 20:11 GMT

Although M-B denies that any design defect exists, they did produce a
heavier version connecting rod. However, I recall something about it
having limited availability which doesn't make sense but that's what I
read.

The problem is well known, especially to owners of the engine. I believe
I may have some pictures of the connecting rods and will try to email
them to you directly. I'm not an email expert so don't be surprised if
nothing appears.
Tom

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