Crankcase oil separator/catch can. A tale of woe.

[Growlerbearnz]

For a couple of years I've had a simple oil separator and catch can in my crankcase vent line. Just something I threw together, a steel box with drain plug, stuffed with stainless steel wool. It seemed to work ok, catching maybe 200ml of oil between oil changes, but the intake pipes were still a bit oily so it wasn't catching everything.

BMW use a centrifugal style oil separator on some of their cars, and it's a cheap part- I figured it would be ideal for my smoky van. Here it is from an X5:

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The neat thing is it is self draining- simple, I think, just plumb it into the dipstick tube, like so:

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Here it all is in place:

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IMG_20150629_111939 copy.JPG (43.67 KiB) Viewed 4203 times

What I didn't appreciate is that BMW have a very complicated PCV valve setup to balance the vacuum in various parts of the engine. I don't. Result? Oil was sucked up the dipstick tube, filling the separator, and flooding the intake manifold. Suddenly my idle speed jumps to 1500rpm (and climbing) and the exhaust starts blasting out blue smoke as it begins to run on its own engine oil.

This is called Diesel Runaway and it is very, very bad. I realised what was happening pretty quickly and turned the engine off, and it took a terrifying 5 seconds or so to stop- I was very, very lucky.

I think I'm going back to a regular, manually-drained catch tank.

Update: Or maybe not: the BMW separator works really well, so I've left it and plumbed its drain pipe into a jar, which I'll empty manually.

[TieMyShoe]

at least it stopped feeding on its own oil. To bad it didn't work, was a good idea.

[Erich]

I use a simple stainless cylinder situated under the driver's seat. I apparently came out of an L300 in Japan and I bought it from CCA. It seem to work well. A little tricky to mount as it eliminates the first leg of the intake pipe.

[Big-Bird]

First off, glad that you got the run-away under control...those can be very scary.

There is some good and some bad information out there about Oil Catch Cans for both diesel and gas applications.

When it comes to diesel engines the best rule of thumb is to collect it and dump the can out at regular intervals(every oil change is best). Having the collected fluid flow back into a diesel engine may sound like a good idea but it all depends on where the fluid is fed back. Personally the misty oil is loaded with fuel vapours that only serve to reduce the viscosity of the motor oil over time.

The other issue to watch out for is when the oil catch can is cold....as in winter conditions. Cold oil can thicken in the mesh, screens and the tubes which can cause back pressure in the breather tube. This backpressure has been known to pop seals/gaskets in the valve cover so you get oil everywhere which poses not a only risk to the engines ability to lube itself but also a serious fire hazard. The catch can should be placed close to a heat source..prefererably a coolant line which won't melt any plastic fittings and tubes that are commonly found on the ebay-specials. Not sure if a person really needs the can with the sight glass/tube. If you empty these things at every change you shouldn't have an overfill problem...which means you could theoretically locate the catch can nearer the exhaust system to keep the catch can warm.

The big truck industry has an AIR-SHUT-OFF safety system that automatically blocks the intake air in a run-away situation. Very cool device but its not meant for small passenger rides. Its intended for big rigs and other heavy equipment.

[Growlerbearnz]

Thanks for the feedback! I've had a mesh filter type catch can for a while, and it worked ok, I just thought I'd be able to upgrade to a centrifugal style separator and save myself the task of draining the can at the same time

I still have the BMW centrifugal separator in place, I've just run the drain into a jar which I'll have to empty manually. The separator is doing a much better job than the mesh catch can- the intake pipes are now clean and dry, whereas with the catch can they still had a bit of oily residue.

[Big-Bird]

Hey Growler....care to define cheap???? Are these available on ebay? Personally the cetrifuge type separator is ideal and the fact it can drain into a jar is perfect. I like the slim look and could likely adapt it to my L400. PLeas tell you didn't buy this new from the dealer..cuz thats not cheap!
And X5's are not that common in the scrap yards around Canada...Perhaps if they are more common in NZ you and I could work out a deal and a used unit could be mailed to Canada?

BMW use a centrifugal style oil separator on some of their cars, and it's a cheap part- I figured it would be ideal for my smoky van. Here it is from an X5:

[Growlerbearnz]

US $11 (For example: http://www.ebay.com/itm/New-BMW-E53-X5- ... 1577540268) though the one I ended up buying came from Australia (http://www.ebay.com/itm/271250261551) because it worked out cheaper once the shipping was included.

From the BMW forums it appears that a failed PCV valve (common on X5's) will also clog up the separator, and a number of people replace both PCV and separator at the same time. It would explain why they're fairly easy to buy online.

The one I bought was probably a cheap knockoff rather than genuine- there was some plastic flash rattling around inside it which I had to extract with a screwdriver (I didn't want it coming loose and being sucked into the engine!)

[Krazyistkarl]

[img]http://images.tapatalk-cdn.com/15/07/05 ... 0c7671.jpg[/img]

I bought this water debris trap, and two 3/4 threaded to barbed fittings for either end for $20. Bottom screws on and off. Installed it a few days ago, so far no oil collected, the oil mist might just be going right through it.