I might be inclined to do a compression test, to see if all the cyls are in good order, at 92 K miles, they should be, but who knows...

Im trying to think of something that could cause that kind of pressure in the crank case to force the oil up.

When you run the car at idle or in neutral in the driveway can you see the oil comming up into the air filter housing,

If you left the oil dipstick out, does oil come out there?

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1984 Euro 300SDC, (4spd standard)
1986 Toyota Landcruiser Diesel HJ60 5spd X2

Gone but not forgotten (some sold, some stripped)
1983 300 SD, 1985 300 SD, 1983 240D, 1986 300 SDL, 1985 300 SDL, 1983 300 D, 1984 300 D, 1985 300SD, 1987 300 SDL, 1983 300 SD, 1985 300 TD Euro, 1983 380SEC, 1990 300 D, 1987 300D, 1982 300D, 1982 300D, 1994 E420, 1987 300 TD, 1987 300 D, 1984 300 D

Here's what I would do: Buy some flexible hose the same size as your breather hose. Run the hose from the valve cover to near the bottom of a milk jug. Run another hose from near the top of the milk jug over to the manifold. You will have created a kind of oil separator. The fumes from the engine should still be able to travel over to the manifold but any oil should accumulate in the bottom of the jug.

Theoretically, the air filter should not make a big difference since, unless you have the older style intake with a butterfly valve, there should be virtually no vacuum in the intake. However, if your oil fumes are plugging up the air filter, this will cause vacuum in the intake manifold and suck more and more fumes from the engine back into the engine.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The car runs strong... if there were a compression problem, wouldn't the car run weak? (I don't know the first thing about doing a compression test... )

I just went downstairs and did the oil dipstick test... With the car at idle, absolutely nothing comes out of that hole (with engine cold).

You got me thinking about something... I remember tightening up the screw clamp that I placed long ago on the upper breather elbow (the one connecting to the top of the valve cover), and this shortly before this problem started occurring. Is it possible that, when the screw clamp was not this tight, some pressure/fumes escaped from there and, now that it is much tighter, that pressure is causing this issue? (the breather hose connects to the manifold intake JUST below the air filter housing...) Perhaps, that's something I should try (loosing up that screw clamp) and see if it fixes things.

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

I'd rather try that experiment with the bottle connected to the lower part of the breather hose, if I can get to manage it... (it saves time...) I'll try that later today.

I'll also try loosing that screw clamp - it might just be as simple as that...

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

By the way, just in order to test things for a couple of minutes, is it safe to run the engine with the air filter/air filter housing off the manifold intake?

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

If you're talking about the inlet to the intake manifold, I don't see the point of attaching it there. There is virtually no possibility that the oil is coming back up thru the intake manifold. It is almost certainly coming thru the vent hose off the valve cover.

Yes it is ok to run it for a few minutes with the air filter removed.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

No, I'm talking about attaching it to the lower end of the breather hose that comes out of the valve cover...

I'll experiment in the early afternoon: breather hose (tube coming from valve cover, or vent hose to use your wording) into plastic bottle, and will take off the whole air filter housing to see if oil sprays up forcefully from the intake manifold (while the vent hose is disconnected from there).

That should tell the whole story...

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

I can't think of anyway that oil would come up out of the intake. I think you'll get oil in the bottle. But then again, stranger things have happened.

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No matter how many times you explain it to me, I'm still right.....Surf-n-Turf

I concur. If it sprays up, we definitely want live video!

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Very funny

OK, I did that test and

from the intake manifold: not one single oil drop
from the breather hose (from the valve cover): not one single oil drop
from the vac pump hose that goes to air filter: PLENTY OF OIL!

So the diagnosis is, according to what was said before, a faulty vac pump diaphragm (and possibly valve checks).

Very strange is that the brakes seem to be working fine (maybe they never did, so I wasn't able to tell), and that there was no oil in the vac lines that I checked, and that the hose from pump to air filter looked clear - all of which would point elsewhere than a pump diaphragm failure... Anyways...

At this point I have two questions...

Where is most advisable to get the vac pump diaphragm (and valve checks?), online or from a local dealer? (if I can save 20 bucks, to me it's all bread from heaven)

Even though I looked at the pictures suggested in an earlier post, I still don't feel I understand the correct procedure for operating on the pump... Is there a tutorial somewhere, or can someone explain the procedure step-by-step?
Also, are we sure that I won't need to remove the radiator on the 240D in order to work on the pump? (the space between the front of the pump and the radiator, after removing the fan blade and its housing, seems awfully limited to me...)

Thanks so much for the invaluable help all of you have been providing!

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

Check here with Phil. I think when I bought mine a few months ago, ******** had the best price by quite a bit. Make sure you get the correct parts. There is an early and late vacuum pump. I think you should have the early.
Pull the cover off the pump, it's a simple job. I did it on a 617 without removing the radiator. You should have equal or more room.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

OK. How do I establish whether I have the early or the late vacuum pump?
The cover is in the front of the pump, facing the radiator, correct?
Could you mention the tools you used? A screwdriver and... what else?
Is it advisable that I also replace the valve checks at the same time? Are they as easy to install? Should I get two (I understand two valve checks go to the front and one to the back) or all three?

Your specific suggestions are very much appreciated...

Thanks...

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

Ordering by year should solve the correct pump issue. Allen wrenches I believe are required to remove the pump cover. Yes, replace the check valves. They just drop into place. Only two that I recall. The check valves are in the pump. I've never of heard of the pump having 3. I don't understand why it would need threel

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The earlier pump will have two vac lines attached to the front of the pump, the later one has only one vac line. I'm 99.9 % sure you have the earlier pump. Basically what you do is remove the flat head screws that hold the front plate on. Do so in a cross pattern, not in ring pattern. Then give it a pull and it will come off. underneath that there is a singular center bolt, I believe it is a hex head, I forget the size. Undo that, then the diaphragm, disks etc. pull straight out as one unit. Remove what ever you have to to give yourself enough room to work in there. When I did mine I could not find a step by step which is why I posted pix. I'm sorry I was too half a$$ed to do a full on pictorial. It really is pretty straight forward. If you decide to do this on your own feel free to PM me and I"ll give as much advice as I can. Oh but I can't really help ya with the check valves. Do a search you may come up with something on that.

Some edits: The two front main vac lines are held in place by a bracket with rubber gromits directly on the the lines. Just like the way the clear line is secured to the air cleaner. OK, the clear line is secured this way in two places, (air cleaner, bracket) . You will need to "pull them off the bracket". Be careful, at this age they are brittle. You don't want to crimp or crack them. Again this is pretty easy. You do not need to remove the two lines from the front plate. If they are off the bracket you should have enough slack to move that unit up and out of the way. Again, be careful.

When I say remove the screws in a cross pattern, I mean if you start at the screw in the 1 o'clock position, the next one should be at the 7 o'clock position etc. Just break them free at first, then go around (cross pattern) and take them all out. replace them the same way.

I'm sure the 4 banger gives you more room to work than I had. I also like lots o' elbow room so maybe some of the stuff I removed was overkill. (under the hood in general). I would think that at least you will need to remove the fan shroud and PS belt. No exotic tools are needed for this operation, although I may have used vice grips (gently) when seperating the disks from the diaphragm. Hmm, that's all I can think of right now. Between the instructions that come with the kit, my pix, and this thread, you should be able to do it in an hour or two. Good luck!

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Sonny


86 190D N/A 2.5L Auto 265k "Ruby" -Sold-
79 300D 242k "Condi" my first -sold- RIP
2013 chevy sonic hatchback - had to for work

My brakes, locks and shut off were still working. Eventhough the diaphragm was leaking oil.

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Sonny


86 190D N/A 2.5L Auto 265k "Ruby" -Sold-
79 300D 242k "Condi" my first -sold- RIP
2013 chevy sonic hatchback - had to for work