How much blow-by is too much?

[woolyAcres]

I'm curious how much blow-by is too much. When my engine is warm and I remove the oil dipstick, I get what I think is a significant amount of air pressure and small oil droplets flying out. It's not enough pressure to push the dipstick out if it's not threaded but it's very noticeable. I ask because my machine really seems to struggle when loaded and then a little bit more load is added. For instance, when running the brush hog this past weekend in some short but thick grass, the machine would be doing okay until I hit a small rise and then it would lug down so badly that it almost stalled. It's not a gradual lugging down but more like all at once. I don't think it's simply the throttle arm moving but I won't swear to that. I did have that problem and thought I fixed it by tightening something. I've got a replacement washer in my Hoye shopping cart as I type this.

The lugging down and difficulty I seem to have with my 5' brush hog got me thinking about what might be going on. As I started to look into it blow-by came up. What things should I be looking at if I'm concerned that the tractor isn't producing what it should be. How hard is a compression test on these 2-cylinder models?

Any thoughts would be appreciated. She starts right up and generally, the tractor portion, works okay. I'm not looking for more projects on this machine but I wouldn't be surprised if there are more to come, it was priced to reflect that. I'm just trying to figure out which projects need attention and which can/should be ignored. I'm just about done with the brush hogging for the year so sustained heavy loads are nearly over until next spring. I'm sure she'll get through the winter as-is, but I'm curious what I should be looking for.

Thanks.

 

[EddieWalker]

It's too much when you lose more power then you feel acceptable. Once it starts, it's just a matter of time until you have to rebuild the engine. For me, I had oil coming out of the dipstick and PVC valve. I figured it's a dead engine anyway, so I ran it until it didn't have anything left. Then rebuilt it.

 

[normde2001]

The 5' brush hog is too big to start with, but as far as blow by, it totally depends on when you are ready to overhaul it. There should be a vacuum in the crankcase

 

[California]

A modern car with a PCV (and a throtle plate) will have vacuum in the crankcase, but I don't see any mechanism on these old diesels that pulls a vacuum.

I agree a 5 ft hog is too big, you're working it at 100% output more often than it was designed for when new.

And I agree with Eddie, I would just keep on running it until - working within its design limits - it doesn't give the performance you require for your tasks. I would expect hard starting due to low compression would be the first problem to appear.

A compression test is difficult on these. There aren't glow plugs in the cylinders so the only access is removing the injectors, and just getting the injectors out was a nightmare for me when I replaced mine. So low compression affecting starting is a substitute, simpler way to assess adequate compression.

 

[normde2001]

"A modern car with a PCV (and a throtle plate) will have vacuum in the crankcase, but I don't see any mechanism on these old diesels that pulls a vacuum."

Could be, except that my YM2000B shows a slight crankcase vacuum on my manometer. IT has a PCV and pistons (with good rings), all that is necessary.

 

[4570Man]

Does it blow white smoke out the exhaust while it is running?

 

[woolyAcres]

Does it blow white smoke out the exhaust while it is running?

No. Smoke is pretty clean. There's a bit of smoke at start up and it can blow some dark stuff when it's really loaded with the brush hog, but overall I'd say it's not bad at all.

 

[Billrog]

Is your crank case vent plugged or the hose pinched ?

 

[woolyAcres]

A modern car with a PCV (and a throtle plate) will have vacuum in the crankcase, but I don't see any mechanism on these old diesels that pulls a vacuum.

I agree a 5 ft hog is too big, you're working it at 100% output more often than it was designed for when new.

And I agree with Eddie, I would just keep on running it until - working within its design limits - it doesn't give the performance you require for your tasks. I would expect hard starting due to low compression would be the first problem to appear.

A compression test is difficult on these. There aren't glow plugs in the cylinders so the only access is removing the injectors, and just getting the injectors out was a nightmare for me when I replaced mine. So low compression affecting starting is a substitute, simpler way to assess adequate compression.

This is probably a pretty fair assessment. I think the brush hog is manageable in pastures to 'clean them up' after the animals have had their fill. It's really just some thistle, a bit of golden rod, and a stray multi-flora rose bush. What I was cutting the other night was actual grass and that seemed to be too much. It doesn't start hard, or throw lots of smoke so the compression can't be that bad. I'm going to just go with it. I was thinking that if a rebuild would make it less taxing with the 5' brush hog, that might be done for about the same price as getting a smaller brush hog. But I'm not truly interested in doing either with winter on the way. I think I'll focus on getting my loader sorted out and leave it at that.

 

[woolyAcres]

Is your crank case vent plugged or the hose pinched ?

That's actually a good question. I don't know but I'll look at that tomorrow. Thanks.

 

[woolyAcres]

I agree a 5 ft hog is too big, you're working it at 100% output more often than it was designed for when new.

I can't disagree with this but what's the best way to tell when it's working too hard? Lugging down? Temperature? Oil pressure? I have installed an oil pressure gauge and I have the temperature gauge that I can hopefully install soon. Would temp and pressure give a decent indication of load?

 

[4570Man]

Lugging down is the best method. As long as the radiator is clean it shouldn't over heat running the PTO 540 rpm. You can pull a 5 foot cutter with any tractor capable of lifting it, but you will have to go slow. Your tractor if I read the specs right has 19.7 PTO hp. I have pulled a 5 foot cutter behind a Kubota L2550 and a Kioti CK25. I wouldn't want any less cutter behind either tractor.

 

[California]

I think the simplest measure of working it too hard is if it won't hold its rpm. If your cooling system is in good shape and you have good oil in it etc then loading it sometimes until it will just barely hold its rpm won't hurt anything, that's what it was designed to do. Oil and temp gauges should remain in the 'reasonable' range if the cooling system meets spec.

My experience has been I've had to shift down a gear to mow back up a gentle slope that I could easily mow in the downhill direction. Just climbing the slope loaded the rig - with 4 ft mower - too hard if I was cutting tall wet grass. I doubt I could mow that stuff in either direction taking a full cut with a 5 ft mower.

Since you already have the 5 ft mower - I would take less than a 5 ft new cut, overlap the previous cut, wherever there is heavy growth. You'll find a balance with what it is capable of.

 

[Neat 1500]

My YM14 has pretty bad blowby. It choofs like a train out the vent tube when it's hot. It is a little touchy to start in winter but not so bad in summer. Uses a little oil but by the way it smokes when throttled up you'd think it would use lots but it doesn't. It's been like this for years and probably will continue to stay like it too.:thumbsup: Keep it a runnin'.......

 

[winston1]

Blowby anything like this? https://www.youtube.com/watch?v=OLwUS_QGOhU

 

[clemsonfor]

5foot is too big in tall and thick grass but if you bush hog a few times a year and do not have overythick grass these ym240/2000 can easily run a 5 foot one. I do all the time now and unless its like i stated above its fine and can handle it, no having to over rev the tractor no dragging it down on slight hills or when i cut grass.

If i think its thicker i just pinch over and take a 3.5-4 foot bite.

You will see mist and like a small exhaust stream out of your blow by tube on the right side of the tractor if its really bad. I have the same thing happen as you describe when i pull the dip stick when running. But think of that crank shaft rotating through that oil at the speed it does!!! I do have a small amount of blow by but to see it you have to have the sun light just right to see it out of the tube and you can feel or maybe not a sligt air movement if you put you finger in front of the tube at Operational RPMs.

I dont think i am looseing any noticeable amount of power at this point and to me is certainly acceptable. There is a youtube video people always link to to show a yanmar with excessive blowby. THe tube looks like a tiny exhaust pipe blowing out grey exhaust!

 

[clemsonfor]

i bet thats the video winston...was pretty sure you were the one who always posts it. I have not clinked the link here to confirm but i bet its the same video i am thinking.

Oh i need to add that my tractor inbwtween 50 hour oil changes i can not tell the oil level changes one bit.

 

[buickanddeere]

If it starts, runs and doesn't more than a quart of oil every 3-4 tanks of fuel . Don't worry about it.

 

[tcartwri]

Make sure you have the right amount of oil in it. Not uncommon to have someone stick any old dipstick in an older piece of equipment just to plug the hole.

 

[California]

Make sure you have the right amount of oil in it. Not uncommon to have someone stick any old dipstick in an older piece of equipment just to plug the hole.

Good point. If we're still talking about a YM240/YM2000 here - my YM240 takes four quarts to show halfway up the hi/low region on the dipstick.

That's how I run it. If I were running it flat-out in hot weather I would add more to top it up, but my use for this one is mostly operating the backhoe or just puttering around carrying something in the loader, not really stressing it.