Crankcase mist - new engine

[veggie]

Hi all,

I finally got the power-plant finished and the engine is going through a break-in period.
When I briefly ramped up the load to 100% (for 10 minutes) I noticed the crankcase breather started exhausting mist.
When I brought the load back down to 50% it mostly disappeared.

Question:
Is this something that can be expected from an engine with approx. 1 hr run-time ?
Does it usually disappear after several hours ?

Here's the video....
http://www.youtube.com/watch?v=fKtY45I5ppk

I will publish a proper "walk-around" of the system later today.

veggie

[Carlb]

Nice setup, 

I suspect that you are getting a lot of blowby right now beings that the rings have not had a chance to seat, I would just place a rag over the breather to keep the mist from going all over the place while you brake in the engine. 

I am not at all surprised to see this on a new engine.  You must load the engine to get the rings to seat, it looks like you are doing a good job of that. 

[Ronmar]

Sounds perfectly normal to me on a new engine.  load it up above 75%, get it to around 200F coolant temp at the head outlet and keep it there for a few hours to break it in.  Even when broke in, there will be a little bit of oil that makes it out with the blowby gasses under heavy load.  An old gym sock pulled over the breather works well to capture the mist:)   

[quinnf]

That's a nice installation.  If the mist doesn't decrease it might start slobbering oil out the B&S muffler you put on the end.  If that happens you can coalesce the droplets of oil into the mist by running the blowby through a piece of 2" PVS packed loosely with coarse steel wool or (better) stainless steel pot scouring pad.  But first things first.

Quinn

[dieselgman]

What type of break-in oil are you using in your system? I concur 100% that these engines will always leak a bit of extra compression past the rings until they are fully seated. Sometimes a non-detergent oil during the first 50 to 100 hours can help speed up the process of wear-in for your rings.

dieselgman

[vdubnut62]

Well, it's not mine but if it was  I'd plumb the mist into the intake, and run the pi$$ out of it, getting it as hot as I dared.
The last tractor I built,(40hp) I ran it just enough to adjust everything, then I hooked it to a 6 foot heavy bushhog,
jerked the throttle wide open and worked it hard. When it got almost to the boiling point, I throttled back, to 1200 or so
and let it cool down to about 195 or so, then wide open, working hard again. After about 3 cycles, it started gaining power,
and stopped heating up. I still have the old thing, and never have had to add oil between changes.
Ron

[playdiesel]

Have you toyed with it a lot? Meaning starting and stopping after short runs? That will cause a build up of water in the oil that boils out the first time you get it good and hot, seen it cause a fog atthe breather like that many times. As they said, run it hard for a spell.

[billswan]

Question:
Is this something that can be expected from an engine with approx. 1 hr run-time ?
Does it usually disappear after several hours ?
veggie

Veggie

The blow by should decrease as the rings seat.

BUT

You have 2 modifications to your roid which may or may not prove out. The long vet tube is kind of small and you may have a hard time getting the oil to separate out of the blow by vapor stream. You may need some kind of oil separator and oil return line added to make it work. The second modification is the full flow oil filter dumping oil back in the original vent location. If to much oil is getting on the crank it could be setting you up for trouble as to much oil is finding it's way up into the air inside the crankcase and then up the vent tube. Is the oil returned just dumped into the crankcase or have you provided some sort of internal tube to get the oil back into the sump without getting it up in the air? By the way just how much flow are you putting through that filter?

Good luck veggie hope what I posted is not the problem and it is just a low hour unsettled cylinder assembly.

Billswan

[veggie]

Billswan,

Thanks for your idea about the breather tube. I will monitor that and modify as needed.

The oil pump rpm creates a flow of approx. 2 gpm.
I fabricated a baffle / oil channel on the inside of the crankcase which channels the return oil directly down to the sump.  I don't  think there is any chance of excess oil hitting the  crank or con rod big end.

Cheers,
Veggie

[rcavictim]

I had a lot of oil mist coming out of my new Changfa 1115 crankcase vent during early trials of the engine under load.  As Ron suggested, I ran a line from the breather output to a port I created in the oil bath air cleaner.  The engine now injests any vapor that might take this route.  It worked like a charm.  This vapor droplets were very, very fine and choked up the air in the fairly large shop which was really nasty on my lungs.  I did the same to the Jiang Dong R175A that I use inside the building as well.

[Tom T]

Ever seen a run away by doning this? Tom T

[mike90045]

Ever seen a run away by doning this? Tom T

It would save on oil changes, stopping it between changes gets dicey though !

[rcavictim]

Ever seen a run away by doning this? Tom T

My 1.5L VW rabbit diesel was supporting a 1/2 load in shop heaters (5 kW or so) unattended after I had never had an issue with blowby but decided to shorten a sloppily long looking breather hose and then left the genset unattended.  It went into a runaway while I was absent and injested every drop of engine oil from the crankcase.  I got back to the shop to find zero oil pressure and the engine running normally at 1800 RPM.  I immediately shut it down.  It had gone way past the point of sucking foam.  There was no oil left available to the pump pickup.  I had to put four liters in to restore oil level in the pan.  I think it may have run 15 minutes without any oil pressure at all.  Amazingly it runs just fine except it has a louder tappet noise upstairs and hot oil pressure is slightly shy of where it used to be, but still plenty good (40 PSI hot, 100+ PSI cold).  It does not burn a drop of oil now nor does it push any oil smoke out the roof stack. No multigrade, I use only straight SAE30W diesel rated oil in my indoor generators year round. I really dodged a bullet that day.  Have I learned my lesson and installed a low oil pressure shutoff yet?  no.     I still start and stop this plant with clip leads.  It has an effective DIY blowby trap installed now though.  These VW engines are infamous for running away from the valve cover vapour breather into the airbox.

[veggie]

Rcavictim,

What is a blowby trap ?
Sounds pretty important after reading your experience with the VW.

Veggie

[rcavictim]

Rcavictim,

What is a blowby trap ?
Sounds pretty important after reading your experience with the VW.

Veggie

It is a type of two port canister installed between the valve cover vent and the intake air box that grabs the airborne oil vapor droplets and allows them to condense and return as a gravity fed liquid to the valve cover breather hole.