# Hydraulic oil in the engine oil



## Dante15063

Oh boy never expected this one. I have a 2013 DK50. I was ready to do 400 hour maintenance on the tractor when I noticed an oil spot under the tractor in the vicinity of the engine oil dipstick. When I checked the level it was completely full! The dealer picked it up and concluded the hydraulic oil was back feeding through the hydraulic pump mounted on the engine. Eleven hundred down later after about 12 hours of use the engine oil level is almost 3/4 inch above the notch. I called the dealer and told them to start researching this problem with the factory. I was wondering if anyone had this experience with their tractor and did they find a remedy. Is it possible the fluid is coming from the drivetrain? Any help would be fully appreciated.


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## marc_hanna

That's a peculiar problem. What does the hydraulic fluid look like? Is it clean?
I would check the coolant as well, to make sure it's not contaminated.

Is your tractor a hydrostatic?


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## Dante15063

Thank you for your thoughts on this. Yes I wondered if it could be cooling fluid but the level has not moved whatsoever. I also thought about diesel fuel getting into the motor oil. But the oil looks very clean and has no diesel smell whatsoever. And the tractor is running very well with no smoke or fumes. So my suspicions point to hydraulic fluid contamination. I considered sending the engine oil to a lab to analyze the contents but I’m not sure it would even show the hydraulic fluid constituent. And the cost is over $400. Ouch!


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## marc_hanna

I think Blackstone labs is about $30USD for an analysis. You just have to siphon out about 4oz of Hydro fluid and 4oz of engine oil. Make sure you don't cross-contaminate the samples, so use a clean siphon tube each time. Theres a lot of crap that gets into the engine oil, but the hydro oil should be pure. If there is a crack or a seal somewhere that's leaking, you might expect contamination in both directions, so the analysis should reveal that.


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## Bob Driver

So it's a repeat failure.... Is there any type of oil cooler that is shared in common between the engine oil and hydraulic oil that could have failed?

Coolant in the engine oil will turn it milky. Fuel dilution is harder to detect. Does it have pencil injectors, or injector cups? Could one of the injector hold-downs have loosened and it be weeping fuel into the rocker box? Detroit had a huge problem with injector hold-down/cup seal failures on their DDEC IV Series 60 engines.

Can you make a plate to cover the hyd pump drive opening to run the engine in order to isolate the problem between fuel and hyd fluid?

If you can't "isolate" the hyd pump, use UV dye and a black light to see if it's fuel in the oil. I believe NAPA still sells the UV dye for diesel fuel

https://autorepairboulder.com/fuel-line-leak-symptoms-and-detection/


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## deerhide

I would say you have unburned fuel getting into your base. Is the hyd. oil level low? How does that hyd. pump hook onto your engine? Is it on the side of the engine? If it was leaking hyd.oil into the engine the hyd. pump must have a leaking seal somehow or another.


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## marc_hanna

Yeah, it seems unlikely that hydraulic oil is getting into the engine oil. Any idea how the shop made that determination?


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## Bob Driver

No load neutral pressure on that hyd pump is probably 300 psi and a pretty good GPM flow rate. Engine oil pressure is around 50 psi and probably splashed lubed around the pump drive opening. Seems to me if it was a failed hyd pump seal, it would be way more than "12 hours of use the engine oil level is almost 3/4 inch above the notch". It's more than likely a slow fuel leak from one of the injectors. UV dye in the fuel under a black light will tell you for sure it's fuel. If you can pull the rocker cover and put a "cardboard dam" up around the rocker cover perimeter to keep the oil splash off the rockers from making a huge mess while the engine is running, the dye will show you the source of the leak under a black light....

https://www.napaonline.com/en/p/NTE788106


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## Dante15063

Wow thanks for all the suggestions! I suppose the oil analysis should be first order. I looked up the website and I’m going to call them and explain my problem. If they can determine the contaminant in the engine oil it will go a long way to a proper diagnosis. As for the UV dye is it possible to add it to the fuel, run the engine for several hours and then drain some engine oil and shine the black light on the oil to see if fuel has contaminated the oil?
As to some of the questions you raised: The hydraulic pump is mounted on the side of the engine with a direct shaft connection. The dealer had removed it and replaced the seals due to microscopic cracks. That is supposed to be the only possible direct connection between the oil systems. That didn’t fix the problem. 
There is an engine oil cooler mounted on the engine near the oil filter but no hydraulic connection. When the engine oil was changed there was no milky appearance to the oil. 
It has been very difficult to see any drop in the hydraulic oil level because it’s capacity is twice as much as the engine oil capacity. It would probably take less than half a quart of hydraulic oil to raise the level of the engine oil to its’ existing level. 
Based on all of your comments it’s making me think I need to refocus my attention on the possibility of fuel infiltration. The analysis should solve that question.


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## deerhide

The test would tell you fuel is leaking into the base......but not where the leak was.


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## Dante15063

You are correct but we will at least be looking for the right culprit


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## Bob Driver

_"As for the UV dye is it possible to add it to the fuel, run the engine for several hours and then drain some engine oil and shine the black light on the oil to see if fuel has contaminated the oil?_"

Yep…. You probably don't need to run it nearly that long. I'd run it for about 30 minutes and see if the oil on the dipstick "glows" the color of Prestone anti-freeze under a black light. Like deerhide said, that will tell you *IF* it's fuel, not the source (there's a couple of ways to test for that), but it will save you of having to send off an oil sample and waiting for the results.

It would also give you the opportunity to take that "glowing dipstick" back to the Knuckleheads that charged you $1,100 to change a hyd pump seal and introduce them to the use of UV dye and a black light as a diagnostic tool for fuel/oil dilution. It's only been around 30 years, but apparently they missed the memo...


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## Paul Miller

I am havin the same problem. How did you make out?


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## Groo

With the pto pumps on the garbage trucks I play with, they put in a weep hole in the mounting flange of the pumps so the transmission don't get taken out in a failure like this.

Could start running engine oil in the hydro system


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## Hoodoo Valley

That just strikes me as a no brainier .the old wet sleeved Detroit's had weep holes same thing to keep coolant from going in de oil



Groo said:


> With the pto pumps on the garbage trucks I play with, they put in a weep hole in the mounting flange of the pumps so the transmission don't get taken out in a failure like this.
> 
> Could start running engine oil in the hydro system


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## Dante15063

First I would like to thank all the members for their suggestions. Since I last posted I sent the engine oil sample out for analysis. It came back with a finding of higher than expected signs of fuel in the oil. I followed that up with a UV test. I had about half a tank of fuel (6-7 gallons) and added the whole bottle. I ran the engine for at least a half hour. Then I pulled the dipstick and checked with the UV light. A bit disappointed to see no difference in the before and after. So next I called another repair shop. He suggested changing out the fuel pump and I agreed since it was not very expensive. When he was removing it I noticed it was apparent it had been removed previously. I’m guessing the original repair shop had taken it off, did a visual and reinstalled. Looking at the pump there were no external signs of defect. Changed it anyway. Since then I have put about 12 hours on the tractor and the engine oil level appears to have stabilized. I think when it is time for another engine oil change I will take another sample and send it in for analysis to confirm that the problem is solved.


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## deerhide

Now, back to the $1100 !


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## Dante15063

I’m trying to forget about that!


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