Oil & Fuel Engine oil blow by

[yanmar1802d]

I have an 1802d 3 cylinder diesel with excessive oil blow-by. Can someone give some advice to what could be causing this? Head gasket, valve, Etc.? I'm not getting fuel in the oil, rather the oil (especially when engine is hot) passing through the valve cover filter/screen pack out the vent tube.

 

[clemsonfor]

Your rings are worn and or cylinder/liners.

 

[yanmar1802d]

Your rings are worn and or cylinder/liners.

Why no fuel in oil or white smoke out the stack if rings are worn?

 

[tjkubota93]

Because the fuel gets burnt and goes out the exhaust like normal. The exhaust goes past your wore out rings, into the crankcase, and out the breather too.

 

[clemsonfor]

exactly your burning the fuel, its still combusting. Its just blowing by the rings...hence the term "blow by". Instead of being contained above the rings on top of the piston then leaving through the exhaust you get a small amout that blows down by the ring down the piston skirt into the oil pan (crankcase). Instead of allowing it to pressureize it there is a tube which allows it to vent to the outside, so the partial pressureized crankcase can vent the combustion gasses, and it carries vaporized oil that is inside the crankcase with it. Think about it its like a hurricane inside the crankcase with the rotating crank and then the blowby gasses in there.

My tractor has some blowby, dont really get any oil but do have pressure blowing out of the tube that varies with rpm's. Tractor runs fine and to me its not excessive. One day i will probably pull the pistons and rering and put new bearing into it but for now i am running it as is.

 

[yanmar1802d]

I expected that rings was the issue, however a friend suggested a few days ago it could be a head gasket. I have read before as long as it cranks and runs well just keep the oil checked and keep running it until i have to rebuild. Do you agree?

 

[winston1]

I expected that rings was the issue, however a friend suggested a few days ago it could be a head gasket. I have read before as long as it cranks and runs well just keep the oil checked and keep running it until i have to rebuild. Do you agree?

Based on your first post if it were mine and I planned to keep it I would go forward with an overhaul. One of these old engines overhauled should last a life time. Doesn't mean everyone thinks like I do, I am confident many would probably run it till it won't crank. :2cents:

 

[clemsonfor]

As for mine, its got small blowby issue as i would call it. You only see it when the sunlight is at the right angle not like its blowing smoke like a tiny exhaust pipe!!

I see plenty of trucks on the road with the blowby pipe doing worse than mine. Plus it cranks on the first hit after i let the decompression lever close so the compression cant be that bad? :confused3:

 

[normde2001]

I expected that rings was the issue, however a friend suggested a few days ago it could be a head gasket. I have read before as long as it cranks and runs well just keep the oil checked and keep running it until i have to rebuild. Do you agree?

There are other reasons, (however unlikely), for smoke/oil out the vent tube. Anything that will cause a + crankcase pressure, such as bad crankcase vent, (lets air in as well as out), or poor oil filler or dipstick seal letting air in. Ideally the crankcase should operate under a slight vacuum.

 

[California]

I have read before as long as it cranks and runs well just keep the oil checked and keep running it until i have to rebuild. Do you agree?

Agree - if this is a tractor you just use occasionally around the house/farm. Rototilling etc. So long as the fumes are not obnoxious and it starts instantly. Just wait until it needs teardown for something else, and repair it at that time.

But a tractor you use to earn a living deserves to be maintained in top condition. If that is the case, overhaul it!