My 240 (81) didn't come with one.

The crank case vents directly to the intake manifold.
I'd like to capture any transiting oil thus preventing it from being burned.

Have any of you retro-fitted a separator? Either stock from another year or aftermarket?


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1981 240D 4sp manual. Ivory White.

I made my own, but I would rather buy a known good brand of one if I did it over (which I might since I'd like to try adding a second vent that a few people have had success with). As long as it's well designed it doesn't matter. I bought a kit from someone advertising on here and it was little better than a straight piece of hose. With these engines they'll need some kind of baffling at least, if not a packing material like bronze wool.

I'm sure I'll be in the minority here, but if the EGR is disabled (as it should be on these engines), what's the harm in letting the engine consume it's own oil vapor? It'll never build up in the intake manifold or create the tar-like deposits that the EGR soot creates. The oil vapor deposits in the intake manifold cause no harm to anything in the intake system or the engine, adding a catch can is just something else you have to maintain.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

For me literally the only reason was eliminating one cause of runaway potential, even if it's rare. Also I don't have the stock air filter anymore so I had to do something different anyway. Was not under the impression that it would add 50 HP or anything like that, to be sure.

Some of it goes through the air filter. In the early versions of the Jeep 4.0L, this is know as blow-by. Its not really blow-by, though.

I removed the leaking OEM can from my 82 240d. I ran a straight pipe to the intake. I got a lot of sludge in there after driving five years. It didn’t seem to hurt anything.

On my 300d (an 85 with no integrated separator - blowby goes straight to the turbo) I added a kit marketed to the bmw n54 guys. The hose diameters worked well. The images are buried somewhere in my Got a 300d thread. I put this in because I was getting a little smoking at intersections when I stopped after a hard run. It has reduced the smoking.

On my 300sd I wanted to do the same thing. I had been struggling with a cylinder with low compression. The engine had a shaking idle but made smooth power over 1000 rpm. I did a leakdown and suspected ring blowby. So I did a ring soak using Berrymans and that really helped the idle. Suspecting stuck rings I did a bunch of other things like switched to synthetic oil with some Marvel oil added to it. That smoothed it out.

So at that point I theorized that maybe just maybe I’m putting more oil down the intake than I can get rid of down the exhaust. I remember from my gasser tuning days, the best way to decarbonize an engine was to just run it with a slightly lean air fuel ratio. So any oil I can prevent from leaking down my intake is oil I won’t have to burn off. And my SD had a decent amount of oil pooling up in the u-tube. So that was my reasoning. Rate in minus rate out is rate of buildup.

Not sure if it worked because I did a ton of other things to the car to stop the shaking. But it doesn’t shake anymore. It has gradually improved so I figure it’s the new oils or the separator. The ring soak made an initial improvement. I may sound crazy but the MMO + synthetic may have actually helped...that is my feeling at least. (Thanks for the tips Rogviler).

Ok that’s a long story. So I made mine out of an old salsa jar with some stainless steel Brillo pads. I 3d printed the hose nipples. Basically free. Let’s see if I can find the images. Oh yeah the top is 3d printed and the nipples are electrical conduit I had leftover from a project. This was an experiment in cheapness.

I know some of you guys don’t believe in this stuff. Maybe it brings some extra complications like flow restriction on the vent which may cause oil leaks on the engine. But I figured I try it awhile and my cars are running better.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

This is exactly where I landed and why I wanted to try this.

I am aware of theoretical flow restrictions -you've not suffered any ill-effect?
I've actually downloaded some of the Cad files you've uploaded over the years.
One off printing on these DIY printing sites is still stupidly expensive... I'll eventually get a maker, but until then, I'm probably looking at third party.

How much oil are you finding, every, let's say, 3000 miles?

PS -do you have a photo of that can, installed?

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1981 240D 4sp manual. Ivory White.

Shern,

Different designs have different amounts of flow restriction. I just have a single plate separating the intake and output. Kind of a vane made out of an old credit card and glued to the lid. The N54 bmw one has a little grill inside and it has more restriction. I’ve not blown out my seals though. My engines are leak free.

I made some flow meters for pcv blowby early in my career. They had vane type oil separators. Just fling the vapor against some walls and make it turn a few corners. Collect any condensate dripping down the walls. Once I removed the obvious restrictions (small holes) the pressure drops mostly came from long runs of hose and the right angle turns. The Brillo pad is pretty low restriction. I tested the design by blowing through it.

I’m so proud of my flow meters. Got to show them off here. I made them first thing out of engineering school. OMG they still make it twenty years later. You can check out the oil separators on each end.

http://www.labcell.com/media/20886/blow-bybrochure%20e.pdf

So, what I was saying is long runs of tubing and right angle turns create a significant amount of back pressure once the obvious restrictions are minimized.

I didn’t put the 3d files up on thingiverse. They actually sucked because the conduits didn’t fit well and required a lot of JB weld for sealing. Also 3d printing sucks for holding pressure. There are microscopic pinholes in my solid caused by the process and it slowly develops a film of oil all over it and weeps. Bottom line I wouldn’t recommend printing my design out without major redesign.

Random thoughts on 3d printing. My printer was really cheap. $199 shipped. Easy to set up and use - watched three hours of YouTube vids. Don’t pay for prints just buy a cheap printer from Creality. Then there is always a big library nearby that often lets you bring in things to print for a tiny fee as long as it doesn’t turn into a weapon.

If I had to make this thing again I’d just buy two plastic elbow barbs from home depot and glue them in with bath silicone or JB weld right down to the lid.

The jar was nice because I can see the oil use. It was also free. I consume a lot of salsa. To mount it I got a magnetic coffee cup holder from a junk yard. I just stuck it to the car.

I haven’t run them 3000 mi. I’d say I collected a quarter cup of oil in 1000 miles.

The SD



The blue 1985 300d

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

https://smile.amazon.com/gp/product/B07KK61723/ref=ox_sc_saved_title_3?smid=AKH7Q6S5LSBBS&psc=1

I've had this one in my Amazon cart for awhile. Next step in slowing down the rate at which the truck marks it's spot in the shop. I'll be watching this thread with interest.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Your blow by meter is fantastic. Boy would that have stemmed a few stale arguments around here some years back...

I'll eventually get around to buying a printer, though I'm kind of waiting for the next gen.

What you're saying re: right angles is interesting. Would that make this unit:

https://www.amazon.com/Engine-Separator-Catch-Reservoir-Baffled/dp/B078H6C2Q5/ref=cm_cr_arp_d_product_top?ie=UTF8

less efficient than the unit posted below?


Had eyes on this one this morning...

I forget the rule of physics that governs flow speed as a function of bandwidth -so I may be off the mark here- but I was hoping to find a catch can with 1/2" barbs to approximate the OEM breather dimensions.

Here's one that even has a dipstick and breather!

https://www.amazon.com/Ruien-Universal-Breather-Aluminum-Separator-Reservoir/dp/B06XKCSHSL/ref=sr_1_14?dchild=1&keywords=oil+catch+can&qid=1619044410&s=automotive&sr=1-14

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1981 240D 4sp manual. Ivory White.

Interesting .

Using less than the stock size hose in any of these isn't going to work well in the long run .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Equation of continuity is what I was thinking of... I think that only relates to fluid dynamics though.

Do you know this for sure or is this an intuition?
In what sense will it “not work well?”

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1981 240D 4sp manual. Ivory White.

I used the same diameter hose and fittings as stock and have definitely had more seepage around fittings and the oil cap, likely from the slight increase in resistance from the baffles and packing. Hence why I wanted to try doubling up the vent lines. Others have reported the cessation of leaks after doing that.

That's good info. I wouldn't have guessed size would be a huge problem, but now that I know, I'll look at other options and prioritize something with decent flow.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

I had experienced the exact same with a smaller diameter hose. Increasing the hose diameter increased the vacuum and reduced the crankcase pressures. No more leaks.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10