861 oil dribbling out the valve cover

Hi, all

same 861 that stumbles downhill. new float, tweaked float, better, but not perfect.

I worked it hard for about an hour today - its first real workout since I replacxed the (cracked) cylinder head. boneyard head, mix of boneyard valvetrain and parts I had, NEW guides NEW valves NEW seats ground and not lapped.

The tractor was blowing some blue smoke from the tailpipe but I am not surprised as the engine was locked up when I got it. Not outrageous. Plenty of power, pulls 5' flail through weeds like nothng is there

About an hour into it white smoke off the muffler and I thought shoot I got troubles, expecting it to be coolant. Its oil, and its coming out of the valve cover. Out the vent, and out around the gasket.

I dont think its a plugged crankcase vent as nothting blowing out the dipstick. The oil is still dark brown/black - not creamy so I dont think theres coolant in it. And theres opil missing- the dipstick was normal when I started it and its low now.

Its cooling down now and I will have a looksee tomorrow morning, but I thought Id ask folks here if they had any ideas.

Thank you!
 
Probably blowby. Check it by putting your hand over the valve cover vent when you first crank it. Once you get it warmed up and working hard it should diminish somewhat. The vent cap should be turned up, it could also need a new gasket. I just put a new valve cover gasket on a diesel and it still leaks a little.If the tank had been off I would have silicone sealed it. As long as its not leaking too much run it. I actually tried to run like a PCV hose by welding the vent cap up with a hose barb to the intake preheater plug hole to suck out the blowby but it didnt work good there. I think I have to find a higher vacuum point. That might work on a Gasoline engine though.
 
When you first crank it up everything is cold so you get more ring blowby. Bringing it up to temperature will expand and tighten pistons and rings in block. When you work it hard it performs even better. The best test of engine condition is a compression test inn each plug hole. Autozone might rent the tool to check that.
 
You could tighten the 2 bolts on top of the valve cover and the pushrod cover also. they dont recommend them to be tightened very much, its in inch pounds. A previous owner could have baked the gaskets. I have a tractor my uncle used for a while and he baked the head gasket. i have never seen a 172 diesel blowing oil bubbles between the head gasket before until i got it back I cant tell you how many tractors I have worked on that were overheating and the problem was dirty radiators. Blow and blow and blow and dirt still keeps coming out. A heat sensor gun is very handy for checking that. My father used to tie a croker sack to the nose grill when in high bushes. when it would start heating up you just get off and give the sack a good shake, then right back to work.
 
I would have siliconed mine down but I didnt check the blowby at the vent first. I will see how it does when I start working it. If oil is coming out the vent cover check the vent screen for being dirty. Clean it with gas and blow it out good. Make sure its all there. I have seen some that seem to have lost some of its mesh. You could also clean the vent surfaces and gasket with starting fluid and silicone them for a good seal, let dry overnight. It wont change the valve cover leak though.
 
I forgot to add that you might want to clean and blowout your oil fill cap. I think it has mesh in it also, it could be dirty and sending the blowby upstairs.
 
On the stumbling downhill, when i took my carb apart I noticed that the float valve would stick in the closed position on mine, I think I stretched the float spring out a little to stop that.
 
Just a thought, but the oil being low after running it for a while, plus the oil coming out of the vent, maybe the ports that the oil is supposed to drain back down from the head to the crankcase are clogged.
 

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