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Hello folks, it's been a while since I last posted, but I do come to the site frequently. Today, however, I have a problem.
A few years ago I rashly agreed to “look after” a friend's Jinma 254, Yangdong engine (not sure of the actual engine model), all about 2000 vintage. Last winter I had to change the clutch, which went well, and addressed a number of hydraulic issues. All ok so far.
This week I got a call that the engine oil pressure seemed normal, but after a couple of hours of mowing, the pressure dropped to Zero. !!!
This was using a sickle bar mower, so it was not highly loaded. And the drop apparently was sudden, rather than the normal pressure drop you might associate with hot oil. Oil levels were normal, and the oil and filter have about 60 hours since the last change. Next day, using the bush hog this time, the same thing happened.
I disassembled the filter relief valve, flushed it by starting the engine and there was LOTS of oil. (Won't do that again!) The engine runs well, no knocking, has usual power, etc. When cool, oil pressures are fine. I can find nothing abnormal.
When I worked on it last winter I had adjusted the valve clearance. Everything seemed clean, so I do not think there is a bunch of sludge in the pan, but I have not looked inside it.
So, I'm not eager to jump into an engine rebuild, and I'm looking for suggestions as to what might be the issue. Other than a pile of sludge blocking the pump inlet, I can't think of anything that might be the cause. I guess that changing the oil and looking for shiny bits might be a good move, but does anyone have other suggestions?
Sure is hot!
Thanks,
Mike / Prairie Dog
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At this point, before you do anything else, I would invest $25.00 and send in a lube oil sample for analysis. It will tell you if the oil is diluted with fuel (you can't always trust your nose), what type of metals are in it, how much soot and sludge are present, and if there is any coolant leaking to it. It will also tell you if the additive package has failed (foaming and aeration of the oil). Or, you can change the oil & filter and see if that helps. My speculation says it won't.
I have to ask what type and brand of oil are you using, and what is the ambient temperature when you are working the tractor?
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Thanks, Guys. I had not thought of an oil analysis, any I have found here have been a lot more than $25… usually over a hundred. Maybe I just haven't looked hard enough. The oil seems very normal.
Also never thought of foaming. It was very hot both days, and I expect it was being operated at full rpm, (I wasn't in the seat). The oil is Canadian Tire, so its quality is suspect… up there with Walmart house brand. But it is the same oil I have used for over 5 years without a problem, although I do not work my engine at high rpm for long in high temperature conditions. I did add oil to about half a litre over the full mark, and the problem has not repeated, but then again the weather has cooled down.
I think I'll change the oil to a better quality of oil, and see how it goes. I'll save a sample, and do the poor man's analysis (cut the filter in half). But, like you, I doubt it will fix it. It will, however, rule out that possibility. If that doesn't work, then off with the pan, as David suggests.
It sure is bothersome to not know!
Mike
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Try here. $25.00.
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That’s entirely possible. There could be an internal crack in the casting and it wouldn’t leak or open up until it was hot enough. These engines don’t have oil coolers like the higher end machines do so they have the oil heat indirectly carried away by the cooling system (the oil can run 10 -20 degrees hotter than the coolant), which is another thing to check. Make sure the radiator fins are impeccably clean when running under high r/m loads when the ambient temperature is high, also make sure the engine coolant passages are clear. A good chemical flush and rinse will take care of that, and the use of a high quality coolant such as Final Charge or equivalent, will make a big difference
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Thanks guys… good suggestions. Since I was not the operator, I have no idea what the coolant temp was at the time, but it was a hot day and he was haying. I know the rad was clean in the spring, and the coolant was new and up to level, but it sure bears checking. Currently I'm waiting for the oil analysis kit to arrive and there has not been a recurrence.
I had disassembled the oil filter relief valve to make sure it wasn't stuck, but never thought of a housing crack etc. As you said, David, “stranger things have happened”.
Mike
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Does the oil pressure reduce slowly as it gets hot or does it go away all at once? And by chance did you restart it after a few moments and the oil pressure came up? I am wondering if it is maybe a restricted oil return hole under the valve cover,maybe the oil is mostly staying up there and starving the sump.But I think that might be unlikely but need to check out.
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Sorry guys, life apparently got in the way of posting an update. First grandchild is due any day now… I don't recall this much activity when we had our own.
As for the tractor:
All I have done is to change oil to Shell Rotella, new filter, and I'm told it now runs just fine, but the pressure is on the low side. I have taken a sample, and expect to get the results soon.
I have come to the conclusion that David is right… the problem is likely somewhere in the oil filter housing. The pressure changes are reported to be abrupt rather than gradual. Relief valve malfunction? Economy oil foaming in exceptionally hot weather? Still a mystery.
Since it seems to be working OK, and we are nearing the end of the season I think I will wait and do any further work in my shop instead of on my back in the dirt. That will also give me an opportunity to drop the pan and inspect a bearing or two.
mike
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