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catch can contents

Koston740

New member
Joined
Nov 1, 2008
Location
York, PA
emptied my catch can a few hours ago ... what I found inside was a thin oily black substance that smelled of fuel. I am running an experimental vent tube from the block from under the intake manifold to vent off some excessive blowby. This is about three weeks worth. plus a 7 or 8 hour trip last week.

I dont really know if this is normal bad or good for this kind of catch can setup.

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i dunno if that's a lot or a little...looks like a lot to me.

Does your catch vent to atmosphere or recirculate?
 
recirculate, so i have negative pressure, keep in mind that there is no baffel system or anything to prevent oil from flying from the hole on the block of place under the intake,

I dont see why its so black, just did an oil change not tooo long ago.

Like I said its watery and smells like fuel, if that means anything.
 
recirculate, so i have negative pressure, keep in mind that there is no baffel system or anything to prevent oil from flying from the hole on the block of place under the intake,

I dont see why its so black, just did an oil change not tooo long ago.

Like I said its watery and smells like fuel, if that means anything.
 
If cylinder seal is relatively good (not much blow-by) and your system for trapping oil BEFORE the can is good, then your catch can is going to capture primarily condensate that gets boiled off. It appears as a thin black fluid that smells of hydrocarbons. You won't capture as much in the summer as you will in the winter. Sounds like yours is working just fine to me.
 
That's still a fair amount of oil content. Oil & water don't mix, so you would see water with oil layer on top if it were just condensate

IMG_8175.jpg


As pointed out, this particular content is seen primarily in colder weather.

As long as you're checking it frequently enough, there's no reason it should be an issue, although a baffled setup is obviously preferable in terms of keeping more of the oil in the motor.
 
That's still a fair amount of oil content. Oil & water don't mix, so you would see water with oil layer on top if it were just condensate

IMG_8175.jpg


As pointed out, this particular content is seen primarily in colder weather.

As long as you're checking it frequently enough, there's no reason it should be an issue, although a baffled setup is obviously preferable in terms of keeping more of the oil in the motor.
 
What is with the TB system and all the double posts? I know I'm only hitting the button once....

If you gently pour some oil and water together - yes, you get a delineation of water on the bottom and oil on top. But the way condensate and hydrocarbons of various sorts get 'mixed' in the crankcase (pretty violent environment) it's like putting everything in a 300HP blender. So what starts as condensed water in the crankcase ends up looking like a thin dark fluid that smells like hydrocarbons.
 
OT question, ive been running a catch can for about a month now and there isn't even a layer of oil on the bottom, just a hazing of oil on the inside. Is something wrong with that? Btw it vents to the atmosphere!
 
What is with the TB system and all the double posts? I know I'm only hitting the button once....

If you gently pour some oil and water together - yes, you get a delineation of water on the bottom and oil on top. But the way condensate and hydrocarbons of various sorts get 'mixed' in the crankcase (pretty violent environment) it's like putting everything in a 300HP blender. So what starts as condensed water in the crankcase ends up looking like a thin dark fluid that smells like hydrocarbons.

They separate again in the catch can. I guess I should have said oil & water don't stay mixed. That's what my photo is of. His is more oil, less water.
 
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OT question, ive been running a catch can for about a month now and there isn't even a layer of oil on the bottom, just a hazing of oil on the inside. Is something wrong with that? Btw it vents to the atmosphere!

Where does your vent tube terminate? Where are you venting? Is there oil spray evident after it terminates? No reason to see any oil accumulation if the system is doing it's job. You won't see condensate until the weather changes.
 
It sounds like your system would collect a lot of oil/fuel due to it's installation on the bottom of the plenum. (assuming this is what you mean)

3 weeks.... if you're driving 3-5k in 3 weeks that is fine, if you're driving 200 miles in 3 weeks that's bad...
 
looks to be sucking oil out of the engine. probably need a better oil separator prior to the catch can
 
I may just remove the extra vent tube all together. after installing it oil still seeps out of the oil cap and cam seal. But i'm sure it does provide some extra ventilation so its not really that much of an inconvenience.

Towermt I thought about using one of those water oil separation used on air compressors. But the oil seems to be staying in the can and not really causing any issues or anything. What are you using?
 
OT question, ive been running a catch can for about a month now and there isn't even a layer of oil on the bottom, just a hazing of oil on the inside. Is something wrong with that? Btw it vents to the atmosphere!

try running a tube from the can back to intake after the AMM, You still need positive crankcase ventilation with a catch can, it might catch more oil then.
 
How's your oil pressure? Could be your oil is getting contaminated by fuel (either running rich, or bad rings or valve guides). When my B21FT was in its final days the oil would go black and smell like fuel, and hot pressure would go from 4bar to ~2 after only a few days.
 
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