My 1980 300D consumes ALOT of oil. I'm talking about a litre every 250 kilometers or so. I get a bit of oil on my driveway but not enough to explain all the missing oil. The car doesn't smoke after initial warmup either.

ANY IDEAS??? I'm worried that one of these days I'll forget and run the car out of oil.

How many miles does the car have on it? Is the car turbo or not? Is the air filter soaked in oil?

Reading all these posts about the latest engine disaster is enough to make anyone paranoid. I check my oil almost every day!

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

The car is a 1980 300D non turbo, approximately 275,000 km.

That IS a lot of oil.....it would have to be smoking if you was burning it at that rate........you need to consider a leak while running......I recomend cleaning the engine with a degreaser to get a idea of where and how fast the leak is. The oil filter housing to block is a prime place for a leak......Not sure if the non-turbos have an oil cooler or not but if it does those lines are another place you can lose a lot.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Odds are that you need reboring, pistons and valve guides but make sure you look before you leap. Do a cylinder leak down test and while pressure is applied to cylinder listen for leakage. If sound is coming from oil filler hole it is worn piston/rings/cylinders. If from intake an intake valve and from exhaust an exhast valve.

You can either bore and use oversize pistons or resleeve and use original pistons. I strongly prefer boring and using oversized pistons because the piston is one of the highest stressed parts in the engine in a diesel and I prefer not to reuse them.

Good luck,

I have seen many diesels which burn a lot of engine oil with NO SMOKE
As an experiment, I ran my OM617 engine on 50% used diesel engine oil. The exhaust did not smell of burnt oil and there was no noticable smoke.

It is possible that you have significant blow-by and the oil vapours are being burned as fuel.
You may have issues with the vacuum pump which if the diaphragm tears can feed a significant amount of engine oil into the air cleaner.
CAUTION You car may candidate for a runaway condition, as the fuel (engine oil) cannot be turned off.
In the event of runaway, you need to stop the engine oil getting to the inlet manifold, or stop air getting into the inlet manifold. Removing vent hoses (from Vac pump / valve cover) will stop oil from those sources. Remove the air cleaner and blocjk the inlet manifold with a thick piece of pine or ply to block the air from getting in.
Obviously, if the engine is in this condition, you will need to keep it in gear and keep your foot on the brake, to keep it stopped. Putting the transmission into neutral or Park would allow the engine to rev beyond redline. Engine destruction would occur soon after.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

"You can either bore and use oversize pistons or resleeve and use original pistons. I strongly prefer boring and using oversized pistons because the piston is one of the highest stressed parts in the engine in a diesel and I prefer not to reuse them." ---- Larry Bible

Larry makes this sound as if you can avoid boring by resleeving and using oversized pistons... this is not true because the bores are bored to each individual piston if you follow the very exacting directions in the MB Factory Shop Manual... which I can not imagine not doing if you want your engine to serve you well after all the work and money you are putting into it.
The Factory Shop Manual gives exact information about checking and reconditioning each part in an engine rebuild... and since we are talking about a non turbo here two factors come into play... first the power output is much less than the turbo.... and the non turbo new pistons are WAY cheaper to buy than the oil cooled annular ring turbo pistons... But if you follow the manual on things like ring land measurement... or compensate by buying special rings which properly fill them you have lots of options once you do a great job of measureing what you have.

Thanks for all the advice, everyone. My brother actually has the original engine torn apart and, hopefully, we'll have that one ready to put back in before this one goes south, if it ever does.

BTW - I've noticed a significant amount of oil on the passenger side of the engine, probably coming from the cam chain tensioner area. Perhaps this explains where the oil is going. When I get a chance, I'll install a new gasket and see if this helps.

Re: blow-by. If this were the case, wouldn't the compression be low? I'm asking because we did a compression test a few months ago and we got pretty high readings.

Technically for blowby,,,if you had regular measurements over the life of the car you might see the relationship... but a one time check is not likely to help...
There are some good threads about this stuff.. but make sure you are not filling up your engine to the max mark on the dipstick... or maybe even check to see if the correct dipstick is installed.. stranger things have happened...
One thing to check if you know you are burning the oil as compared to dripping it out is the valve stem seals... they can allow a lot of oil to get to the combustion chamber while the engine is still in great shape.... and it is a pretty easy and cheap fix...
OH, and be sure to use the updated stem seals if you do this....

I doubt if it's the valve seals, as we replaced them when we replaced the head last fall. I'm going to pursue the leaky cam chain tensioner seal and hope for the best. Fortunately, with a spare engine I can wait to tear apart this one when the other is complete.

the leak you describe from the chain tensioner area is most likely coming from the oil separator tube that connects the oil separator with the crankcase. This is going to happen in an engine with lots of oil usage and blowby.

Good luck,

Quick question regarding the valve stem seals.

I've seen a kit as well as just the seals. Would I need special tools to do the seals, or could I get a way with buying the seals and a new gasket?

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1980 300D 300K KM - parting out
1979 300D 375K KM - parting out
2 300Ds for sale

Just bumping, looking for a response.
thanks

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1980 300D 300K KM - parting out
1979 300D 375K KM - parting out
2 300Ds for sale

If you are carefull, you can install valve seals w/o removing the head. You will have to pull the cam assembly, and don't drop the valves into the cylinders. The valve seals are little more than rubber umbrellas that fit over the top of the valve stem.
The problem is the guides. They are often the real cause of the oil leakage down through the head. They get worn out and can allow a lot of oil into the cylinder head. To replace those you are best to have a machine shop do it, or end up buying more specialty tools than you may want to, with the need to pull and replace, reseal the injection chambers.

I replaced my valve seals last summer without removing the cam at all on my 617 engine. took an old injector and brazed an air chuck onto it, turned whichever cyl I was working on to TDC, and put the air to it. then removed valve springs, and slid the seals on over the little plastic thread protector that came with the seals.

air holds the valves up. needle nose pliers with electrical tape on the jaws hold the valve stem. don't nick them!

still have to remove the cam followers though.
karl