C250td Oily air pipes

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daver - 08 Mar 2008 18:41 GMT

I'm a bit concerned by how much engine oil there is in the air pipes
on my 1998 c250td

There's quite a bit of oil in all of the air pipes from after the air
filter all the way 'round to the intake manifold so I assume it's
coming from the engine breather through the oil separator.

I tried cleaning out all of the air pipes and the separator but the
oil returned almost immediately.

I did think about buying a new oil seperator but as it's a simple
cyclonic system, without any filter or moving parts as far as I can
see, I thought a new one might not be any better.

Does anyone have ideas to remedy this situation?

Thanks

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-->> T.G. Lambach <<-- - 09 Mar 2008 05:26 GMT

Diesels have the problem you describe. The question is how much lube oil
is consumed this way? A liter per 1,000 miles isn't nice but acceptable.

Basically too much air volume is blowing out of the crankcase and
carrying with it lube oil mist. Why is that happening?

If your motor has done say, 250,000 miles, it could need new rings.

Older diesels exhausted their vacuum pumps into the motor so a vacuum
leak somewhere in the car supplied such excess air. Does your motor (a)
have a vacuum pump and (b) if so does it vent into the motor?

Finally, is the engine's lube oil level BETWEEN the notches on the dip
stick. Some shops overfill and the excess is blown UP the air oil
separator's drain tube on hard acceleration (my experience).

Hope these thoughts help.

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daver - 09 Mar 2008 11:56 GMT

On Mar 9, 4:26 am, "-->> T.G. Lambach <<--" <"T.G. Lambach at
NoHamorSpamcomcast.net"> wrote:

> Diesels have the problem you describe. The question is how much lube oil
> is consumed this way? A liter per 1,000 miles isn't nice but acceptable.
[quoted text clipped - 17 lines]
> © 2008 T.G.Lambach. Publication in any form requires prior written
> permission.

Thankyou for your reply. I'm not too sure how much oil it's using -
I've had the car for a year and it certainly hasn't been using
anything like a liter of oil per 1000 miles in the past, but recently
it overheated (nackered water pump impeller) so I've been doing a bit
of work on the cooling system. Actually, I took it to a garage (non
MB) and they replaced the waterpump and thermostat but it still
overheated. After much mucking about with it myself, I tried turning
the themostat around and it now runs at normal temperature... In the
meantime I'd nackered the radiator with radflush so it got renewed
along with ATF cooling pipes, ATF etc...

As part of this, I cleaned the air pipes while they were off and after
a few short runs (to test ATF level) they are dripping with oil again
inside. I hope the car isn't using more oil than before but will have
to wait to be sure.

Haynes suggests that it does have a vacuum pump - I'll have to do some
more investigating.
I maintain it myself so the oil is at the right level

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-->> T.G. Lambach <<-- - 09 Mar 2008 20:53 GMT

The oil in question is a residue, not cosmetically nice but acceptable.
The overheating you cite, if sever, could have killed the piston rings'
temper and so created an oil burning engine with a lot of compression
loss that causes "blow by" into the crankcase. Hopefully that's not the
case.

Suggest you keep a log to determine exactly how much oil must be added
after X,XXX miles for THAT's the important test.

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daver - 10 Mar 2008 16:32 GMT

Thanks for the advice.
A car that uses up a bit of oil I can live with. At least it doesn't
seem to be putting out any black smoke so I think the best thing to do
is keep an eye on the oil consumption over the next few months. And
hope it passes the emissions test in its next MOT in the summer...

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