Why do some people have problems with the breather tube? By FACE PLANT FOR LIFE (Read 2,335 times)

[FACE PLANT FOR LIFE]

I see a lot of people complaining about how their oil spews out of their valve cover breather tube, and to be honest, I've never had an issue with any oil escaping whatsoever. I know that my breather tube doesn't attach to anything (open air), and I know I never lose oil. Why is it that so many people lose oil? Some people report that they lose very small amounts but other people say that their engine SPEWS oil out the breather tube, while I've never had even a drop come out of mine.

The question becomes...why?

[Alleyoop]

Some overfill the crankcase some the hose is blocked some how, some the hose is attached to the air filter and it gets clogged with oil or dirt and then it does not vent so more oil squirts out. Some have the tranny hose going into the valve cover vent hose so NO Venting for either the crankcase or the tranny. Then some have blow by their rings so it is now time for a ring job. It is all about the amount of pressure built up in the crankcase and if it cannot vent it will blow oil out, or blow seals and or gaskets.

[jct842]

Too much oil is one cause. Blow by caused by worn rings is another cause. Any interference With the normal negative/positive pressures in the crankcase is the main cause. When the piston goes up, the crankcase see's a negative pressure, When it goes down there is positive pressure. Any time any thing disturbs the + - you see oil. Failure of the pollution system or a person switching hoses will cause it. I have seen it in some of the older cars where the crankcase vent gets plugged and valve cover gaskets start leaking.

[Bashan]

Simply put, I think a lot of them are commenting on that when they leave the hose hanging lower than it's attachment to the valve cover. If they had tied it off higher it wouldn't be an issue in most of the cases.

[Alleyoop]

Have to put out a MEMO not to leave it hanging

[Bashan]

Nice Alley, real nice. I'm embarrassed. HAR!! Not! Good one.

[LUKE]

Jul 26, 2014 12:02:22 GMT -6 Alleyoop said:

Some overfill the crankcase some the hose is blocked some how, some the hose is attached to the air filter and it gets clogged with oil or dirt and then it does not vent so more oil squirts out. Some have the tranny hose going into the valve cover vent hose so NO Venting for either the crankcase or the tranny. Then some have blow by their rings so it is now time for a ring job. It is all about the amount of pressure built up in the crankcase and if it cannot vent it will blow oil out, or blow seals and or gaskets.

so the bigger the vent hole the lesser the pressure build up.. im gonna drill a quarter coin sized vent hole on the enginehead of my morph. cheap insurance, i learn new things from you everyday alley, thanks

[Deleted]

Jul 26, 2014 10:33:31 GMT -6 FACE PLANT FOR LIFE said:

The question becomes...why?

Some of the answers you have been supplied touch on some possibilities. here is my input:

To answer that question requires an understanding of how the PCV system should be engineered and function.

The PCV system should have a hose attached to the air cleaner box on the filtered side and that should be routed to the crankcase. The hose from the Cam cover should have a calibrated orifice and connect to a manifold vacuum port. Needless to say, it does not.

These little scooters are running very much like a fine 'race car engine', by that I mean they are developing every foot pound of torque they can and still remain somewhat reliable.

The Chinese instead of engineering a true PCV system chose to allow the blowby gases to vent somewhere. This keeps the engine from blowing out seals and gaskets.

On the one I am playing with, it normally vents into the air cleaner box intake hose. I have measured the pressure on this system @ idle  cold, and it was slightly off zero. As it warmed up it slowly increased to 1 psi @ idle. On normal operating temp stable revving it, it developed pressure in excess of 4 psi.

Based on these readings, anyone that continually runs their scooter @ WOT will most likely damage their engine and be blowing oil in ever increasing amounts.

This is far too much pressure and volume for this engine to deal with when properly engineered as a true closed loop PCV system.

If the Chinese had engineered this system with a liquid/vapor seperator it would have been more reliable and oil making its way into the air cleaner box would be almost nil, and could be handled by the engine on the clean air side of the air cleaner box. This would also decrease emissions and allow the capture and burning of HC, not to mention oil pollutants.

Scrappy Dog Scooters, sells what appears to be a 3.0L Mitsubishi  PCV valve that they suggest you buy and install. Don't do it! It is a waste of money and time. Building a liquid vapor seperator would be a far better idea.

Here's a question back at you. Does anyone here have a 3D printer and would like to collaborate on making a liquid vapor seperator?

[richardv]

Jul 26, 2014 15:03:53 GMT -6 Alleyoop said:

Have to put out a MEMO not to leave it hanging

What would we do with out your wisdom?

[Deleted]

Jul 26, 2014 18:26:22 GMT -6 LUKE said:

Jul 26, 2014 12:02:22 GMT -6 Alleyoop said:

Some overfill the crankcase some the hose is blocked some how, some the hose is attached to the air filter and it gets clogged with oil or dirt and then it does not vent so more oil squirts out. Some have the tranny hose going into the valve cover vent hose so NO Venting for either the crankcase or the tranny. Then some have blow by their rings so it is now time for a ring job. It is all about the amount of pressure built up in the crankcase and if it cannot vent it will blow oil out, or blow seals and or gaskets.

so the bigger the vent hole the lesser the pressure build up.. im gonna drill a quarter coin sized vent hole on the enginehead of my morph. cheap insurance, i learn new things from you everyday alley, thanks

you gonna put a hose on that? if not have fun with all the oil comin out and the dirt goin in.

I really hope you're not serious.

[jct842]

Luke won't need any hose on that hole because his morph is so far advanced over all other scooters.

[FACE PLANT FOR LIFE]

Jul 26, 2014 21:27:54 GMT -6 jct842 said:

Luke won't need any hose on that hole because his morph is so far advanced over all other scooters.

His morphous is at least 5000 years ahead of Chinese "junk", right?

I love riding around on a piece of "garbage".

[jct842]

You will have to ask him, it may even more advanced than that!

[jct842]

Oops. Am on a nexus and I fat fingered it

[Deleted]

Jul 26, 2014 21:54:38 GMT -6 jct842 said:

You will have to ask him, it may even more advanced than that!

why does it even need wheels? it's a wonder it doesn't float all on its own.