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.