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What does the inside of YOUR oil separator look like?

SMO

Well Known Member
Friend
I have a Christen system I removed from my 1987 RV-4. I don't know how long it was on there. I took it off soon after I got the plane in 2007, and it has been sitting around my shop ever since.

I was going to put this up for sale and thought I would remove the fittings for transport. Turned out the middle fitting on the separator had been cross threaded so that part is now junk.

I took off the bottom fitting and this is what I found:

Bottom%20Fitting.jpg


Decided to cut the bottom off the can. This is what the bottom looks like on the inside (the silver speckles are from cutting it open):

Bottom%20Inside.jpg


Here is a shot of the whole thing:

Oil%20Sep%20Cut%20Open.jpg


Anybody want to buy my system (minus the separator and the middle fitting)? :D

Christen%20System.jpg
 
What exactly are we separating... ??

Most interesting, Mark!

I had installed a separator on my RV, but removed it before first flight, based on feedback from a respected graybeard. His theory was that the separator returns condensed water vapor to the crankcase along with the scavanged oil, creating more acids and corrosion-enhancing compounds in the oil. Tribological chemistry is beyond my paygrade, but it sounds reasonable. It would be insightful to compare oil analysis from engine with and without oil separator, maybe before and after... Maybe the amount of crud that the separator returns to the case is so small compared to the amount generated as to be a non-issue.

I like a clean belly, but also want to get to TBO. Anyone have real data that transcends hearsay?

- Roger
 
I had made a separator for my rocket and ran with it for a couple of oil changes.
Rather then returning the bypass to the crankcase I collected it in a coiled tube below the separator and then drained that off occasionally to see what was there.
It was pure oil, no sediment, no water, no crud.
Currently my breather vent exists parallel to the floor of the fuselage about 2" aft of the cowling. It has been like this for a few years. At the time I installed it I had a negative 2"Hg. I have not checked the pressure/vacuum since that time but with 850 hours on the engine I have NO drips in the cowling. I do have a nice clean line of oil on the belly, that gets wiped down with each 25 hour oil change.
 
I was not surprised to see this. Maybe it is something specific to the Christen system. The owners manual for my Decathlon said to drain the Separator's bottom hose at each oil change.

I did this at each 25 hour oil change and always found water mixed with oil coming out the separator and hose.
 
The system looks like it rarely, if ever, saw inverted use. I used to exercise mine frequently. I didn't re-install it after an overhaul, because it got to be that the only inverted I did was to exercise the system! It looked good inside after 10 years and 1200 hours.
 
The system looks like it rarely, if ever, saw inverted use. I used to exercise mine frequently. I didn't re-install it after an overhaul, because it got to be that the only inverted I did was to exercise the system! It looked good inside after 10 years and 1200 hours.

And as reported by the OP the pot sat 7 years after removed from service till cut open recently. Right?
 
To Cool

An oil temp that does not reach 212 degrees at the hottest point in the engine is "too cool" this temp will boil the water (and assorted other bad things) into vapor so they can go out the breather. It is generally accepted that a gauge indication of 180 degrees corresponds to 212 ish degrees at the hottest point inside the engine. I recommend that the engine be setup to operate between 180 and 200 on the gauge. Good luck, Russ
 
And as reported by the OP the pot sat 7 years after removed from service till cut open recently. Right?

Correct. The sludge inside the pot is old, somewhat dryer than the sludge I noticed in the hoses when I removed it 7 years ago.

If I ever use one of this type on my airplane again I will scope the inside at each oil change to confirm cleanliness. A better design would allow disassembly for cleaning.
 
wow, during the winter season my oil is generally between 165 to 170. Time to put an additional cover over the oil cooler for the Winter season.
 
The Christen system is very robust. I am sure there are failures and issues, but I have never heard of any. There is nothing in their O/M information that even suggests any kind of maintenance or internal inspections.
I will scope mine as a curiosity as that airplane is currently being restored and a new engine hung on it. The Christen system will be going back into the airplane.

By the way, Christen installation instructions have you take the breather all the way out the back of the fuselage. This is how it is done on my Bucker. Most installs I have seen do not do this.
I put a pan under the breather tube outlet as some very nasty, caustic, water comes out of that tube every flight after shut down.
 
In the process of cleaning everything for my new engine installation I decided to clean my inverted system. The shuttle valve was clean as a whistle. The separator was a different story. I soaked and flushed about a thousand times with mineral spirits. Over the period I collected literally a 1/4 cup of brown particulate matter, the vast majority of which did not stick to a magnet. There were chunks, but mostly fine powder. The previous owner "did not fly much acro" which I'm thinking really meant did not fly any at all.

I'm going to make flushing it an annual event, especially given my recent engine problems.
 
After following this thread and the other one from ASA oil separator that caused a front seal blow, I tried to look at mine.
I have slim fighter separator installed and just out of curiosity, I tried to look inside to see if there is much goop or other junk in there. The unit is a welded unit and cannot be opened without destroying it but using my little inspection camera showed a relatively clean but oily inside. Not a whole lot more could be viewed.
 
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