Go BottomCrankcase ventilation on 950
 | Todd Wilson
Join Date: Posts: 1 
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2002-07-26 40713
Ran my JD 950 in some adverse conditions today. Had to do some bushhog work this afternoon in the Kansas heat that happened to be at 107. I took a few breaks and would open the hood on it and clean off the screen. I would then drink some water and let things idle for 5 minutes and go back to work. I noticed today upon idle the crankcase vent tube was putting out a little smoke. Had not noticed this before and was wondering if this was normal. It only did it at an idle. Tractor performed perfect today and never acted up or gave an indication it was hot. I kept the screen clean and made extra stops today just because of the 107 heat to cool both me and the diesel. Never did shut off the tractor the 3 1/2 hours just let it idle at breaks.
The diesel has about 250 or so hours on a rebuild. Just wanting to make sure this smoking was normal and not something I need to worry about.
I could find nothing in my tech manual other then to take vent hose off and clean every so often.
Todd
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-07-27 40719
There's a couple of other recent discussions on about the same subject. I don't think we have a conclusion but one would be nice.
When I hear of blow-by at idle speeds, and usually exhaust smoke as well, I think of valve guides. However, the thought may be more related to gas than diesel engines. Diesels don't have near as much intake manifold vacuum at idle low throttle positions to draw oil down the guides as gas engines. I guess that's still a possibility with a diesel, although some other characteristics of diesels may be at work that I don't know about. Anyway, a rebuild that didn't include new valves and guides could be the answer.
I wonder what weight of oil is used? Hard use in very hot weather might run engine temperatures high enough to start thinning even a multi-grade oil. I think there are viscosity/temperature charts available for different oils that could be checked to see if temperatures might be getting high enough to thin the oil.
I'm sort of sorry that a conversation in response to Art's slightly cryptic comment about people buying oil formulated for one use and then using the engine differently didn't take off. We were going to our camp at the time so I didn't respond. However, I might be guilty since I use a 0W-30 year around. I do warm the tractor up to operating temperature before moving it and don't work it in temperatures above 80F, which is easy enough to do around here.
I'm not really sure how much lower the 0W-30 viscosity is than 10W-30 during summer start-ups. I'm pretty sure that it thickens to 30 weight at operating temperature--same as 10W-30. I think a real risk is if the engine ran hot enough to start thinning the oil. I suppose it would revert back to a base weight that is thinner than 10W, which would be very bad. This is a related subject where it also would be good to get a conclusion.
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 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2002-07-27 40722
Diesel engines are prone to viscosity break down. The strokes on a diesel engine are long and the compresson is high.
A diesel engine oil has antiburn additives. If you down believe me, fill the engine with gasoline engine oil and see how much you burn. I think that you can have viscosity breakdown after hard use and consequently oil burn. If the oil has broken down then the small broken components of the oil will be released as vapour out the breather tube.
We like to think that all the engine oil is the same. In truth each can of mineral oil you buy is different. It is to specification, but will behave differently to the stresses placed on it in the engine. Some of the variation we seen in the rate of oil consumption is probably related to this. Synthetics are more consistant and will provide more even performance.
Also be advised that engine oil has surfactants in the oil and will absorb some water into the oil when left sitting. When you heat the oil, during running the vapours will be released. This is one of the reasons that you need to run the engine to temperature regularly.
I have seen both examples with my 750 JD. ....
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| Todd Wilson
Join Date: Posts: 1
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2002-07-27 40725
I run valvoline 15w40 fleet oil for diesels. I change it probably way more then I need too. This oil in the tractor now has about 3 hours on it and yesterday it got almost 4 more on it. It was 107 outside real temperature. The temp light never came on at all (it does work) and I stopped and cleaned the screen many times yesterday. Just noticed some smoke at idle out the vent tube and never noticed that happening before.
Todd
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 | Art White
Join Date: Jan 2000 Posts: 6898 Waterville New York
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2002-07-27 40726
Most tractors will breath some out the tube when at an idle after running at full load. That still desn't mean that you will have any noticeable oil consumption or that you have harmed your engine. It is wise to moniter it as if you get to the point that it is dripping oil out of it than you have a problem. ....
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| Todd Wilson
Join Date: Posts: 1
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2002-07-27 40732
Thats kinda what I was figuring and hoping for. It was real hot yesterday and the tractor was worked pretty hard. I did stick my gloved finger up to it and it was just some smoke.
I dont abuse this tractor but I do work it hard several times every summer. I also take extra care of it in regards to maintaining things like oils and grease.
Todd
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 | Billy
Join Date: Oct 1999 Posts: 975 Southeast Oklahoma 
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2002-07-27 40736
It may not be blow-by at all. There has to be a way for the presure to leave the crankcase. The inside of a diesel engine gets extremely hot, so a little smoke would be natural. You just happen to notice it.
Billy ....
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| Fitch
Join Date: Jul 2003 Posts: 23 Southern California High Desert
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2002-07-28 40762
Todd, I think you were doing everything right. I don't think there is a problem based on what you wrote. You are making the work like it was designed to and exercising due diligence about the temperature. Good on ya.
Its early Sunday AM, the coffee is good (fresh ground Kona - a weekend treat), I feel like rambling on a bit - so the rest is optional.
I run my JD 770 mowing brush on the horse trail with the 513 brush cutter mower here in the high desert when it is pretty hot (105F or more) some times. That's to hot for me to do a lot of physical labor, so the tractor gets to work while I sit in the seat. I have seen what you describe while doing this. Didn't cause me any concern. The farm tractors of my youth would do the same thing.
The crank case gasses have to go some place and the breather tube is designed for that. As long as it isn't using oil (or any other fluids in unusual quantities) and the temperature is kept in the normal range it shouldn't be a problem. Its good to do a complete fluid level check (all the dipsticks and coolant over flow tank) before starting the tractor into a hard work session - that way you have a definite bench mark should something unusual happen. You probably do this.
Keeping the radiator screen clean is a real good idea. I love that removable screen - the tractors I drove growing up(CAT D2, JD 60, Farmall F-20 with steel wheels, Farmall M, Farmall 400, International 340) Didn't have a nice easy to clean screen like that.
The Kubota L4200 (I think it was a 4200 - it was supposed to be about 40 hp?) and dual spindle Brush Hog I drove to mow about 10 acres of knee high mature field grass and brush in PA ~two weeks ago had a screen - it came out sideways and was a tiny bit more difficult to re-install but still easy compared to a radiator (although the engine side covers were hot enough to be uncomfortable to remove with bare hands). The grill on the Kubota also came off easily - a feature. I ended up removing and cleaning them about every hour. It was also my first experience on an HST drive tractor - very nice for mowing with a Brush Hog - I think it would be wonderful for loader work. I'd prefer gears for tillage, but that's probably just my experience which up to now has all been with gear drive tractors - some with hand clutches.
The screen can clog up amazingly fast when mowing in deep field grass and brush - its a piece of cake to clean compared to the radiator. Mowing the horse trails here in So. Cal. I watch the temperature gage - when it moves up noticeably (it usually runs about 1/4" into the cold end of the green band on the gage) I stop, let the engine idle, pull the radiator screen, brush it off, remove the grill (grills didn't remove easily on any of our tractors years ago either) and brush that off, then go back to it. Sounds like what you were doing.
The good news is that by the time one is done with such a mowing day, the volatile contaminants in the crank case and hydraulic fluid should be all gone!
Fitch ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-07-29 40774
Guess my comment about valve guides was an exercise in engine theory--even then most smoke from upper cylinder oil burning goes out the exhaust. When I read the original post I thought the blow-by had become permanent after the hard hot use. That was a problem with my reading. Concluding that there's no real problem always is good. The main thing is to keep engine temps within the normal range and use an oil speced for the outside temp. I used to run my cars and motorcycles hard sometimes, and yes there is temporary blow-by.
Rad screens always are things to check regularly. I've also been surprised how fast air cleaners can clog and how much sand gets into them. I guess the sand shouldn't be all that surprising since loader buckets go up and down close to the air intake. Both overheating and obstructed air intakes can cause black exhaust, which is another thing to watch for.
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