I think you misunderstand.

The problem the OP has is that he's not sure what's a normal amount of oil in the crankcase breathing pipe. Perhaps he'll post a picture showing what's sitting there at the moment...

...I was saying that if he wasn't prepared to do the borescope thing and I assume doesn't want to make any other measurements or mess about with compressed gas and leak down testers then starting to take a look at the manifolds is the next step.

You can't see much in a cylinder with out a borescope if the pre-chamber is removed so there's no point in removing it if you don't want to go the borescope route.

Looking at the manifolds is much easier and less likely to cause damage to what you've got - removing pre-chambers is a pain in the arse - there's a good chance the locking rings will break and besides a special tool is needed (either real or self made).

More oil in the exhaust manifold than the intake would indicate valve stem related trouble => exhaust manifold wet

More oil in the inlet manifold than the exhaust manifold would indicate would indicate too high crankcase pressure => exhaust manifold sooty but dry or drier than the inlet - oil is being burned

If you remove the manifolds and you can't come to any conclusions then - big deal! You're one step closer to the next stage => remove the head...

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I agree with about 95 percent of what you are saying.... except I think you are a little pessimistic about taking the percombustion chambers out... many good threads, tools available to rent from members the last I knew.. etc...

I really do not understand how ' the next step ' if manifold inspection is inconclusive...is jumping straight to TAKing off the HEAD....
the next step in terms of logical ( economic ) inspection involves taking out the precombustion chambers and checking for bore condition.
AND borescopes are cheap these days compared to the ' good old days'....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Found two threads, neither with the Mercedes special blow by measurement tool listed. Also checked the FSM, no such tool was found.

Great compression but lots of blow by?

Smoke from valve cover

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Even with a borescope, you won't be able to see all surfaces of the cylinder due to focus and angle issues. Unless you have a very expensive borescope like what surgeons use to look up your rear end.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

How's this for a test method?

Run the far end of the crank case breather into a double necked round bottom flask (secured in the engine bay), with a filter over the second neck to prevent oil vapor loss, but allow gas pressure to not build. Hell I' could even throw a condensor over it, or rig up a "catch" can with a vent on it. Cap the crankcase breather hole on the intake manifold and drive to for 50 km.

If I get anything even close to 100mL of oil in the flask, then I know it is all due to oil loss out the crankcase breather.

But, does this get me any closer to knowing if I can just rebuild the head, or if I need to address the cylinders?

__________________
1980 300GD Cabrio

Here are the professionals doing the blow up test..... at 1:20

https://www.youtube.com/watch?v=BtpMTb1gR9w

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Seems like a lot of effort compared with starting to look at stuff, however, if you could catch a large percentage of the oil coming out and measure it then you are on the way to a diagnosis.

If the oil escaping via the crankcase ventilation route is close to the amount of oil you add to the engine then there is a problem with the cylinder wall sealing and this will be more so than the oil dripping down the valve stems route.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

So, I ran this test over the weekend. It was very simple actually. I plugged a length of heater hose I had lying around into a two necked pyrex bottle and clamped that to the air cleaner (I happen to have plenty of lab glass and clamps lying around as well).

A couple of observations:

First, the blow by is pretty heavy and even with a bunch of steel wool jammed in the bottle much of the oil vapor was not captured. From a cold start I drove ~ 50 km and only recovered about 1/10th of the oil I have been consuming. Nonetheless, a fair bit of the oil I'm burning is going via the crankcase breather tube dumping into the intake manifold.

Second, I left it sit like that overnight after the test drive and on the next startup did not observe any blue smoke coming out the tailpipe. I would have expected that if the valve stem guides/seals were a major contributor, it would still smoke at start up even after redirecting the breather tube.

So, it seems to me like I'm looking at rings/pistons/cylinders as the main culprit. I wont know for sure until I dig in and start to disassemble the engine.

I have been trying to figure out how this could have happened during the 4 years the last owner had it (odometer went from 60,000 to 90,000 km). I know that before he bought it it did not consume oil. Based on the repair records I can find he was outsourcing most/all the maintenance (oil change receipts) and within a year of him getting it he had the rear main seal replaced. I suspect that it might have been leaking enough oil at the time that it might have ran low enough to overheat it and create the burning problem I have now.

__________________
1980 300GD Cabrio

Did the oil burning issue exist and was it disclosed to you when purchased or did it develop under your ownership? Leak down test next? Have you checked out the engine breathing system to make sure nothing is blocked?

In 81, Mercedes changed to a cyclonic air cleaner housing that does a better job of separating the blow by gas and returning the oil mist to the crankcase. Not sure if you can upgrade yours to cyclone or if it will help.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

If either low oil or overheating with lack of coolant got too far. This could have taken the temper out of the rings at one time. Usually it is the compression rings that get hit first. Kind of unusual for a rear seal to go out that early but excess sitting around may have been a factor.

The block if milage is truly accurate has only 70 k miles on it so It may not need other than rings. To add another possibility. Hopefully the rings are not broken but compression from cylinder to cylinder seems pretty good for this to be a possibility.

I was also wondering about oil leakage into a cylinder from the head gasket but that would not produce the excess blowby a block with that milage has.

Very low total milage with bad storage conditions. The piston lands may have developed oxides that are immobilizing the rings somewhat.

Aluminium oxide is really tough stuff. They use it to produce decent sandpaper even. At the same time clearances on diesels are small and that's why they seem to be able to sit much longer without seizing. Much may hinge on the accuracy of the 116 kilometers indicated.

Basically what I am thinking is other than some unusual occurance occurring at some time in the past. If you are certain of the milage. This should not be the situation you are experiencing. Now by running a vehicle like this excessively in desert conditions without additional sand filters a condition like this could occur.

I know it was not burning oil when the guy I bought it from got it at 60,000 km and it was burning oil within 500 km of my acquiring it at 90,000 km.

Not sure what you mean by engine breathing system.

It is a w460 with an OM617.931 (derivative of OM617.912) and has a "trumpet" style air cleaner as all w460 300GDs did. The crankcase breather hose plugs directly into the intake manifold.

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1980 300GD Cabrio

I firmly believe the mileage to be true and accurate. I have records from the second owner going back to 1999. He bought it with 40,000 km on the clock and sold it 8 years later with 70,000 km. I bought it 4 years later from the third owner with 90,000 km on it and have some repair records with appropriate mileage in between. I have also spoken to the original owner who brought it over from Germany in 1981 and he only used it as a "farm" vehicle since it was not exactly brought into the country with the full knowledge of the DMV.

I agree that the engine does not have the hours on it to show these symptoms, yet it does. That's why I was hoping that marvel mystery oil, synthetic oil and Italian tuneups might improve the situation. They haven't.

Excess sitting is definitely a possibility.

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1980 300GD Cabrio

Did the person you bought it from experience the same 1 quart of oil consumption per 500 km? Did he mention it and provide any clues as to how and when it started?

"engine breathing" is the Mercedes FSM nomenclature. Look up FSM 01-040 for 82-85 300D, it describes both the old (77-81), and the new (82-85) "engine breathing" systems.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I never met the guy who owned it from 60k to 90k km. I bought it through a third party.

I Googled "FSM 01-040 + OM617" and got back an OM617.95x service manual. Perhaps I wasn't clear, this is a Gelandewagen with a normally aspirated 5 cylinder OM617, not a w123 turbo diesel. The air intake looks more like a euro w123 with an OM617.912 than a US version mercedes 300D.

I don't mean to be rude. I'm honestly asking if there is a breather system besides the intake manifold, that I should be looking at.

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1980 300GD Cabrio

I have no access to a Gwagen manual. I did look at the engine compartment of Fulcrum's GWagen when he stopped by for some 240D parts a few years ago and everythimg in there looked familiar including accessories. Did Mercedes design an intake for the GWagen that's different than a W123 of the same year? Can you post some pics of yours? I was suggesting that you take a look at FSM 01-040 to see if the cyclone air filter housing may be adapted to your engine to lower oil consumption.

Too bad you have no access to the most recent PO. I do not think 3-4k miles avg per year can cause that much oil consumption if it was maintained properly. Something not nice was done to the engine. Ran out of oil? Overheated? Driven pedal to the floor before the engine is fully warmed up? I am out of ideas also.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked