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!

 

[yanmar1802d]

I've just noticed that the radiators plastic reservoir is discolored. Looks like there could be a little oil in the water. No water on the oil dipstick though? Head gasket?

 

[winston1]

Should be getting bubbles in the reservoir if oil in there. That would be head gasket.

 

[yanmar1802d]

Haven't noticed bubbles, but no doubt there is oil in the anti-freeze. Drained the radiator and it's there. Again no water in the oil? Again the oil blow by is from the valve cover and not the crank case. Is this rings, head gasket, cracked head(hasn't been hot) or valve issues?

 

[winston1]

"Again the oil blow by is from the valve cover and not the crank case."

The valve cover and crankcase are all one as far as blowby is concerned. They share the same cavity.

 

[kwin]

"Again the oil blow by is from the valve cover and not the crank case."

The valve cover and crankcase are all one as far as blowby is concerned. They share the same cavity.

This true but to me if the blow by is from the crank case tube then the rings are wore out, if the valve cover is blowing oil I would think valves leaking. Maybe not just thinking

 

[Neat 1500]

I think too many people are over analyzing this, blowby is caused by rings leaking compression into the crankcase plain and simple. If it was a crack in the block,head or liners if it has them more than likely water will be in oil or vice versa. If it still runs OK, and the fumes dont kill you keep running it till one of the 2 happens....... hopefully not the second one

 

[yanmar1802d]

There is a little (very little oil in the water). Does this suggest a crack (hope not), or maybe just a head gasket. Ran it pretty hard yesterday bush hogging. Only problem was oil being blown through the top of the valve cover and out the vent. Ran hard for about 3 1/2 t0 4 hrs.

 

[kenmac]

you shouldn't get oil in the water from a blown H G. If you do, It'll be the 1 st that I've seen

 

[normde2001]

There is a little (very little oil in the water). Does this suggest a crack (hope not), or maybe just a head gasket. Ran it pretty hard yesterday bush hogging. Only problem was oil being blown through the top of the valve cover and out the vent. Ran hard for about 3 1/2 t0 4 hrs.

Yanmar Tractor Parts BODY BREATHER 00
I have never seen a YM1802, but does the valve cover vent look like this? If so I would assume it works just like a pcv valve on your car. A check valve allows air out but not in. I would check/clean as necessary. If check valve rattles it should be good. Older Yanmars do not have this.

 

[winston1]

This is what the breather on an 1802 looks like. Note the rectangular box with the hose coming off. Word play on rocker arm cover or crankcase vent, one and the same.

After going back and looking at the 1802/2002 parts list it does show one like you posted Normde.