Catch Can Contents Returned To Crank Case??

[CoosawJack]

I have never considered returning Oil Catch Can Contents to the Crank Case but someone on another forum says newer technology allows OEM Catch Can Contents to be returned to the engine oil.....REALLY??

Is it safe to do this and if so WHY EVEN HAVE A PCV SYSTEM??

Thanks and HAPPY NEW YEAR!!

 

[Imp4]

I would only do this if there were a justifiable reason to do so. It would need to some how improve the performance of the engine.

I can't think of any reason why this would improve the performance of the engine. So the answer is a hard no.

I'll don my flame suit and make the statement that catch cans don't accomplish anything worthwhile anyway. So it's like piling bunk on top of bunk and expecting a miracle.

Happy new year!!

 

[Olas]

A properly designed air/oil separator is a vital part of an effective catch-can - the vapours need plenty of time and opportunity to condense/coalesce/fall out of suspension.

Moroso sell an exhaust crankcase vent which maintains inlet cleanliness and provides continuous depression for better ring seal, better power, better mpg etc.
This removes the need for a catch can, is simpler and lighter and cheaper and lower maintenance, and is the best overall solution to the blowby/pcv/ivd issue.

 

[HangFire]

The purpose of the catch-can is to prevent motor oil from becoming deposits on the intake valves. Along the way it also catches water vapor, and breakdown products of oil. I suppose, for a zero-maintenance system, that returning all that to the sump would allow it to be removed in the next oil change. All of those things are already present in used motor oil anyway.

 

[eljefino]

Originally Posted by HangFire
The purpose of the catch-can is to prevent motor oil from becoming deposits on the intake valves. Along the way it also catches water vapor, and breakdown products of oil. I suppose, for a zero-maintenance system, that returning all that to the sump would allow it to be removed in the next oil change. All of those things are already present in used motor oil anyway.


Since this is the stuff that "boiled out" of the oil, it just didn't want to be there in the first place. Returning it to the sump gives it another opportunity to boil out in a never-ending cycle. If we had a problem of losing an entire quart of oil to "evaporation" and the catch can held most of it, I'd say put it back... otherwise, no thanks. (And I wouldn't want something capable of evaporation lubricating my engine anyway...)

 

[Rhymingmechanic]

What vehicles are doing this? Is it meant to prevent valve buildup in direct injection?

The PCV system scavenges combustion gases that get past the rings, so they don't vent to the atmosphere. A catch can collects oil from the PCV stream, so it doesn't get sent into the intake and burned.

If an OEM installs a catch can, they must really think it's needed. Making it drain back to the crankcase would be ideal for most owners, who won't drain it themselves. Requiring service for some new thing people haven't heard of would also be bad for marketing.

I'm interested to know how these systems work, if they're an actual catch can and not just a glorified oil separator. If a catch can got full, I guess it would make an instant mosquito fogger as the liquid got sucked up and burned.

 

[bullwinkle]

Acidic byproducts of combustion (burned motor oil that got past the rings, blowby including acidic water vapor, etc.) back in the crankcase?? That doesn't seem very smart to me, at least without testing it somehow to see how much nasty stuff is in there (guessing mostly bad). The stuff that gets through a PCV system gets burned in the combustion chamber, not dumped back into the sump.

 

[HangFire]

I agree, even if some percentage is just lighter fractions of the usual 0w-20 oil, I don't want the rest of that junk back in my crankcase. But the modern auto industry is very resistant to new, high maintenance items, look at the lengths gone to by VAG and Ford/Navistar to avoid DEF. So if catch-cans ever become OEM, I bet they'll just dump back into the crankcase.

 

[AZjeff]

The reason for this is to make it hands-off. The general public wants nothing to do with something that has to be drained, no matter how easy and what do you do with the icky stuff? Since the spooge can't drip onto the ground back it goes. Trav has posted some illustrations of complicated OEM catch cans.

 

[bullwinkle]

Only OEM one I've ever seen was on my '02 Dodge Cummins Ram 2500, it had a little catch bottle that mounted on the front timing cover, it caught some crud, I usually emptied it at oil changes (into the drain pan).

 

[Silk]

Originally Posted by Rhymingmechanic
What vehicles are doing this?


My 1996 Volvo has this system, so it's been around awhile. It's not GDI, but had the manifold off last week, and the intake valves are nice and clean. Only oil goes back in the sump, water vapours into the intake system, and gunge just seems to build up in the tank and hoses. The Volvo system is a problem because it's not very accessible and is made of nasty brittle plastic...made more accessible of better materials and I'd be happy. I have no problem with whatever goes back into the sump, it hasn't sludged up or worn out the engine yet.