I noticed a bunch of smoke coming out from under my hood and popped it open, found the crankvase vent hose thing off and a ton of smoke pouring out from inside.

I assume that, said smoke = blow-by. There was quite a lot of it. (Interestingly, though, I've never had any trouble starting my car even down as low as about 40F, it starts up instantly with about 1 second of cranking.)

It looks to me like it just popped out of the retaining ring thing, so I'm going to put it back in, but my questions are: what could have caused it to pop out in the first place, and what can I do to keep it from doing it again? Is something clogged somewhere and it backed up and escaped there?

Thanks.

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

I put a hose clamp on the crankcase end of the hose to keep it from getting loose. The other end seems to stay put OK.

Depends what side it came off of. I know there is a grommet in there on some of them and there is a rubber elbow on some others. If it came off it is most likely that it is old and brittle and any rubber components should be replaced. If you do have enough blow by to blow that puppy off I can't imagine it would start that well let alone run well. Look for brittle rubber parts and post back.

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2003 Dodge Ram 2500 Cummins - Georend fully built trans, Banks Big Hoss Bundle, Smarty Tuner, 5" turbo back exhaust. 500 HP and 1100 ft/lbs to the ground.
1979 Mercedes-Benz 300CD - Lost to a four car pile up on 275, Thank You Michigan Drivers.
1986 Mercedes-Benz 300D - Sold, Euro non-turbo car.

I found a rubber neck piece which looked worse for the wear; I've got it cinched up now and with a new hose clamp and it's all good.

Blow-by is enough to make the oil cap nearly bounce itself clean off the assembly if it's loosened while the engine is running, but for reasons that escape me, the thing starts okay and runs fine (except for being at about 1/2 fuel efficiency.)

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

Have you adjusted your valves lately? If not you might check that first and see if it helps with the blow-by.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Probably not for the last 100,000 miles. I'll order some wrenches and so forth.

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

Yikes! They're supposed to be adjusted every 15k or so!

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I've owned it for 8k, and I guarantee the two previous owners didn't maintain it at all.

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

Those wrenches come in very handy. With a helper goes quickly. Take pics if you can of the linkage so you can put back, perhaps a new gasket as well.
Biggest problem, getting the cover back on!

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83 SD

84 CD

You might want to remove and wash the hose out with a solvent and check it. Might be some buildup in there causing a less than ideal air flow and causing the engine to retain more pressure. These cars have been in service a long time.

It's surely a good thing to adjust the valves, but it will have no effect on blow-by.

It seems pretty easy to do a valve adjustment - I may try one myself as I am due in a few thousand km. Any tips? I have the factory manuals of course, but surely you guys have plenty of practical experience

Not a big deal, but as mentioned, special wrenches help.

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83 SD

84 CD