Oil & Fuel Diesel mixing with motor oil

Craiger-mags · Dec 20, 2007

I have a Chinese tractor sold under the name of Hercules. It has a Benye 345 enging. Its a reverse steer I use it with a snow blower. It works very well and runs and starts strong.

I have noticed recently that there is a lot of thin oil or fuel blowing out of a discharge chute on the side and at the same time notice that the oil has thinned out some. This happened before and when I changed the motor oil it looked like diesel fuel had mixed with it. I could be wrong its just that the oil was thin.

I am looking to the experts out there to find out what might be happeing and better yet how to fix this problem. Could this be typical of diesel tractor engines.

Thanks for your help

Craig in North Idaho

bluechip · Dec 20, 2007

a little blowby seems common on these engines. I think Hercules was benye and if so they probably use the same Y385 engine common to many chinese tractors. Jinma adds a plastic line from the oil breather to the intake manifold on these engines to help reduce this blow by. Unfortnately excessive blow by generally indicates worn piston rings. A compression test might shed more light. The only way diesel can get to the oil (at least in theory) is past the piston rings. If your engine is running properly, no excessive black smoke etc (that could indicate too much fuel passing through the injectors) than it is likely rings. It is critical to change oil between 30 and 50 hours and at least every 100 hours or once a year after that.

RonMar · Dec 20, 2007

How many hours are on the engine? If it smells like diesel in the oil, then it probably is.

Another thing that sometimes happens with hydraulic pumps driven off the aux geardrive at the front of the engine, is that a shaft seal will go on the pump and hydraulic fluid will leak down into the sump. This of course would not smell like diesel.

Usually diesel in the oil is caused by running under low load/excessive idle. Under these conditions, the rings don't seat and combustion chamber temps are low so diesel condenses on the liner and leaks past rings into the oil. Another problem can be with poor injector spray pattern which leads to incomplete combustion. Same result, liquid diesel gets past the rings. A cracked ring or piston skirt could also allow more fuel to reach the sump, but you would probably note more oil burn and blue smoke in the exhaust.

Another possibility like the hydraulic pump mentioned above, is that the shaft seal on the fuel injector pump is bad and dumping fuel down into the sump via the accessory geardrive case.

Soundguy · Dec 20, 2007

bluechip said:
The only way diesel can get to the oil (at least in theory) is past the piston rings. .

Hmm..seems like the injector pump shaft seal, as ronmar mentioned is a quite real possibility.. vs 'the only way'.. etc. I've seen it happen on other tractors before.. etc..

soundguy

bluechip · Dec 21, 2007

The possibility of it coming from the injector pump is pretty small. The injector pump crankcase has its own oil resevoir, the fuel is in the head of the pump so to get to the engine crankcase it would have to go past the injector pump pistons, dilute the 3 or 4 oz of oil then lead out the seal on the end of the injector pump into the timing gear case... Also, there is the blow by from the crankcase vent. If it is not running particularly well, an injector could be dribbling fuel and washing past the rings.

Does the engine get fully warmed up and run for fairly long periods? or quick short runs. this could also contribute. How long does it take for the oil to thin out? Does the vent blow smoke with clean oil?

Soundguy · Dec 21, 2007

Guess we would also need to know the condition of the oil in the injector pump sump as well.

soundguy

greg_g · Dec 21, 2007

Craiger-mags said:
I have a Chinese tractor sold under the name of Hercules. It has a Benye 345 enging.

Just for clarification, did you mean to type 354 instead of 345? If so, the engine is a TY395. If so, there might be another way that diesel fuel can get into the engine sump. It's not necessarily the same engine, but I have a ShanDong 395 that recently did the same thing to me.

Either way, 15W40 should have a specific gravity values around 0.88 and #2 diesel should be around 0.81 (water being 1.0). That unfortunately means that the fuel will be floating on the oil in a cold engine sump. If it was water, it would have settled down at drain plug level. But things can't always be that easy.

So. Short of draining the entire contents of the sump and letting the layers settle, the next best way is to closely inspect the dipstick. Get a clean paper towel and lay it out on a flat surface as close to the engine as possible. Pull the engine oil dipstick from a cold engine, and immediately lay it flat on the paper towel. With luck, you may be able to determine if there's diesel above the oil on the dipstick.

Same with hydraulic fluid. AW32 for example has a specific gravity around 0.845, which means it too will float on 15W40 engine oil. But - hydraulic fluid on the dipstick should be cleaner than the engine oil AND should not smell like diesel fuel.

It's a ballpark test method, may not work in all cases. But worst case, all you've wasted is one paper towel and a little time.

//greg//

Craiger-mags · Dec 30, 2007

Greg, You are correct that the engine is a TY395. I trained the oil today and got just a little over 8 quarts of very thin liquid, which I believe to be a mixture of diesel and oil.

I am still learning about tractor engine operations and what is what and how it works so it will take me a little time to find these various mentioned parts on the engine in order to correct the problem. Fortunately I do have a operations manual/parts manual for the tractor so that will help.

Any other advise you have many be helpful at this point. If not I appreciate you and all the others that have responded to this problem.

Craig in North Idaho

greg_g · Dec 30, 2007

Well - the list of liquids that could migrate into the engine oil is short; water, fuel, hydraulic fluid. But without the Benye manuals, we're gonna have to approach this generically. Assuming you drained the 8 quarts into a bucket, coolant would have turned the oil sorta milky - an emulsified look - before eventually settling to the bottom. There are a number of ways that coolant can get into the engine oil.

Assuming you use a medium weight diesel engine oil (like 15W40), enough light weight hydraulic fluid (like AW32) will thin it out. Whether it lightens or darkens the mixture, depends upon the relative cleanliness of both, so it often it's difficult to discern a color change. Given time however, hydraulic fluid should eventually float. Hydraulic fluid can usually only migrate through a bad seal on an engine driven pump.

Diesel fuel will definitely thin engine oil, and in many cases lighten the color - until they too separate. Like hydraulic fluid, fuel will eventually float. But unlike hydraulic fluid, you can smell the fuel - even moreso after separation. As with coolant, there are several ways that fuel can end up in engine oil.

So to start the troubleshooting process, you have to be 100% sure just WHAT is entering the engine sump that's raising the level and thinning the oil. Once you positively know WHAT it is, then you can start narrowing down HOW it's getting in.

Also - when the tractor's cold - open the radiator cap too. Look for any sooty looking residue floating on top the coolant. Using your finger like a dipstick, sometimes any black stuff might stick. You might also find it on radiator cap rubber seal. Not that I expect you to find any, it's just that dirty coolant can be another clue.

//greg//