Hydraulic oil coolers
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Thread: Hydraulic oil coolers

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    Hydraulic oil coolers

    How much should hydraulic oil cool temperature drop from the input to the output of an air-cooled hydraulic oil cooler? I know there is a range but what could cause a tractor with less than 900 hours have a drop of only 4 degrees using an IR gun. Engine is cool, fuel cooler has a 15 degree drop.

    From just the physics of the situation, flow rate (too fast or slow) and lack of flow throughout the whole cooler could be the only problems I could see. Just hard to believe it could be a clogged cooler with that few of hours.

    On this cooler, there is a large input tube and large output tube. The small tubes that parallel through the cooler are all cooler than both the input and output. The tube on bottom is about 10 degrees cooler than the rest.

    Regardless of any details surrounding the cause of the oil cooling, temp drop should be more significant than 4 degrees shouldnt it?

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    Keeper of the GTT Cookies dieselshadow's Avatar
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    There’s a lot of factors at play here. We need to know more information like ambient air temp, cooler inlet temp and outlet temp. Has the tractor been worked prior to your measurements? Why are you curious and checking the temperature all of a sudden? Is there an issue you haven’t shared yet?
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    If airflow is good through the cooler , then the oil must be passing through too quickly to be cooled. What model do you have? Is oil getting hot? What temp is the oil? What is air temp?


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    Quote Originally Posted by dieselshadow View Post
    There’s a lot of factors at play here. We need to know more information like ambient air temp, cooler inlet temp and outlet temp. Has the tractor been worked prior to your measurements? Why are you curious and checking the temperature all of a sudden? Is there an issue you haven’t shared yet?
    Sorry I was trying to just keep it more generic than my particular situation, thinking it could solicit more responses.

    The reason I became interested is I've been having an on-going issue with my STOP light coming on when my hydraulic temp reaches about 156F. I'll paste another more detailed post that didn't get any replies so you can see all the things I've done. But to answer your question:

    Outside air temp was about 90F.
    Inlet temp 135f Outlet temp 131F
    Inlet temp 141f Outlet temp 137f
    Inlet temp 150f Outlet temp 146F

    So you see, it seems to always be only 4 degrees cooler going out than coming in. That just seems like very little compared to like the fuel cooler or a radiator.

    Here are my other details:

    6115d hydraulics temperature
    I have a 6115d tractor that, when the pto is engaged, slowly has the temperature creep up to to the point where the stop light comes on. This can be anywhere from 45 min to 1.5 hours depending on rpms and implement. This happens on bailer, batwing mower, hay cutter.

    I'll list all of the things I have done but what I think is a key to this is the temp difference between the inlet on the hydraulic oil cooler is only 4 degrees hotter than when it comes out. This can't be enough can it?

    My one thought was that the oil bypass valve wasn't allowing the oil through the cooler but I removed the output hose, started the engine and oil came out. The flow rate I can't confirm but it was a lot. Regardless, any flow going through the cooler should cool more than that shouldn't it? with only a 4 degree drop, it picks up more than 4 degrees as it goes through the system so builds and builds.

    Here is all I have done with no change in results:


    Hours: 1200

    PROBLEM:

    After an hour of bush hogging with a batwing mower OR bailing hay (anything with the pto), my hydraulic oil temp creeps up to over 156F (as measured at the sight glass and oil cooler with IR gun) and eventually the stop light on the tractor comes on.

    THINGS DONE:

    Changed Hydraulic oil and filter
    Ensured coolant is topped off at max fill
    Removed output hose from cooler to and made sure oil is flowing out
    Made sure rocker arms are not up
    Confirmed oil level is between the lines on the sight glass
    Made sure the engine radiator and fuel cooler are normal temps. Hydraulic cooler is the only one hot
    Confirmed with JD that there is no sump filter that could be clogged. Its only filtered by the hyd. filter
    Attempted to bleed air from the cooler but not sure how to do that since the input and output are on the bottom.
    Used only hyguard oil and filter
    Cleaned the cone-shaped caps on the tractor(I don't know what they are called) where hydralic cylinders get locked in place. LIke a float valve. They were pretty cruddy inside.
    Washed all coolers (radiator, oil, fuel) thoroughly
    Cleaned air filters
    Removed hydraulic cooler and ran water through to confirm there is flow.
    tested temp diff on input/output of hydraulic cooler. No matter what temp, there is only a 4 degree drop across the cooler.
    IR tested the hydraulic cooler itself. The small tubes are about 10 degrees cooler than the main tubes. But the main tube exit is still only 4 degrees cooler. The bottom small tubes are a good bit cooler than the others. Might indicate that one set of coils is clogged. But that shouldn't cause this I would think.




    OTHER INFO OF INTEREST:


    When the PTO is engaged and the engine is revved, some oil dribbles in from the top of the sight glass and it has air bubbles. Eventually makes the sight glass a little cloudy from the bubbles. After stopping, they clear within 10 min.

    ONLY REMAINING GUESSES:


    Air bubbles in hydraulic oil not normal and causing the overheating or accumulate in the cooler until it is turned off
    Internal hydraulic leak (how would I know?)
    Open the bleed valve on the radiator while running? Not sure how that can help.
    Check to make sure filler cap vents are clean

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    Quote Originally Posted by jd110 View Post
    If airflow is good through the cooler , then the oil must be passing through too quickly to be cooled. What model do you have? Is oil getting hot? What temp is the oil? What is air temp?


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    Thank you I replied to your questions in another response to DieselShado

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    Usually when the STOP light comes on you should have another warning light lit also. Hydraulic oil temp does not seem to hot. How did you determine it was a hydraulic problem,
    Last edited by RAM2940; 09-04-2019 at 04:19 PM.
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    Quote Originally Posted by RAM2940 View Post
    Usually when the STOP light comes on you should have another warning light lit also. Hydraulic oil temp does not seem to hot. How did you determine it was a hydraulic problem,
    The other indicator is the 'Engine Information Indicator'. According to the manual, the reasons for a STOP include:

    • Low engine oil pressure
    • High hydraulic oil temperature (PowrReverser/Wet Clutch Tractors)
    • High coolant temperature
    • Water in fuel
    • High manifold air temperature


    Just strictly through deduction do I assume it is hydraulic temp because
    1. It only comes on when the PTO is active. I can get the stop light, turn off the pto, and run it forever without getting the light on. If I resume the pto, the light will come on again. That rules out almost all of the causes listed except high hydraulic oil temperature.
    2. I use the IR gun and the light only comes on after the hydraulic temp gets over 151 or 155 degrees. 170 causes seal damage so I assumed 155 was a reasonable cutoff temp.


    On my 6115d I cannot figure out how to read my engine error codes without consulting a dealer. Can't seem to bring them up from the console. I even have the shop manual.

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    There is a ground issue on some older x series. If you turn on the pto or any other electronic draw the engine temp needle pegs out.

    I honestly cannot believe 155 is the working temp limit.
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    The same issues have been known to happen when the engine oil pressure sensor starts to fail, but if you believe it is in the hydraulics try to find the hydraulic oil temp sensor, try changing that if not very expensive, or try testing the sensor, varible resistance throughout its temp range. Could be getting out of tolerance. Or if you can post the fault code, someone should be able to determine was it means. Also check fuel filter for water in fuel, Change the fuel filter if it has not been changed.
    Last edited by RAM2940; 09-04-2019 at 05:57 PM.
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    Quote Originally Posted by RAM2940 View Post
    The same issues have been known to happen when the engine oil pressure sensor starts to fail, but if you believe it is in the hydraulics try to find the hydraulic oil temp sensor, try changing that if not very expensive, or try testing the sensor, varible resistance throughout its temp range. Could be getting out of tolerance. Or if you can post the fault code, someone should be able to determine was it means. Also check fuel filter for water in fuel, Change the fuel filter if it has not been changed.
    Yes when I first got it the stop light came on while I was just driving and I quickly changed the fuel and pre fuel filter and it went away.

    Those are good points about the sensor for the hydraulic oil temp sensor and the oil pressure sensor temp.

    On the oil pressure sensor, do you mean engine oil or hydraulic oil? If it was the engine oil, it seems the problem would persist if I continued to drive after the machine faulted and the pto was disengaged but I could be wrong. It very much only will come on if the pto is engaged.

    As far as electrical, it never comes on when the temp is below 150 ish for sure. I say ish because I have to keep the pto flowing to get a good temp reading and I won't leave it running if the stop light comes on. Too scared !

    The idea of the oil passing through the cooler too fast would be true if some of the coils were plugged. I had taken it off to wash but that probably wouldn't have cleared them up. The bottom coil is about 10 degrees cooler than the other coils. I don't know if that would be enough to make a difference or not. One plugged coil in the loop of about 8 coils.

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