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  1. #1
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    mt180mhd

    Default MT180HD HST Problem

    I hope this is correct forum. Please move or merge if not. Thanks.

    I'm having an issue with the tractor not moving 90% of the time.
    However the PTO and loader work fine. Linkage is good and not binding. Brakes are fine.

    Pickup screen and canister filter are clean/new. If I open the cap to check oil level it is fine.
    With the engine running I can see shaft turning inside reservoir.
    No oil is splashing in neutral, or when HST fails to operate.

    If I then open the plug on top of the HST, I can see the "butterfly"?? moving back and forth
    when control shaft is moved. Oil is being splashed around, clean, no air bubbles or foam.

    With tractor raised if I can get the HST to engage the wheels do turn, and then oil is splashed around
    inside reservoir where you check oil level. I can change forward/reverse; high and low gear, 2wd and 4wd work.
    HST does make a lot of noise, but I always thought it made a fair amount of noise and seems the same.

    Continuing to activate control shaft, wheels will just stop turning, oil stops splashing, but "butterfly" continues to
    move back and forth. With engine off I can see pistons moving in and out with "butterfly".

    I've yet to check pressure, as I haven't been able to find fittings to connect a gauge.
    Suggestions?

    I'm thinking charge pump. But I hope this hasn't damaged HST.

  2. #2
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    mt180mhd

    Default Re: MT180HD HST Problem

    A few more thoughts.

    I think the "butterfly" I was describing above is called the "swash plate", if that helps anyone.
    Was thinking charge pump but not anymore. After looking at the routing it looks like the 3 point lift
    is directly fed via the pump. If I raise it all the way up past the stop it will almost kill the engine.
    This tells me it has plenty of oil and pressure.
    So back to the HST.
    Took the low pressure relief out again, checked the spool, saw no scuff marks.
    Neutral valve plungers can be moved back and forth from both sides. I can feel the spring resistance inside
    after removing the piston(s).

    Onto the high pressure relief. After removing the cap/pin/washer/spring I took out the casing this time.
    I hadn't pulled them out before. Manual states to thread a bolt into it and pull it out.
    Even shows a persons hand as the method of removal.

    I couldn't budge them from either side without using a lever assist. I got them out but it seemed
    way to hard based on the manual. I didn't see any score marks and the popit looks good too.
    The casing is very hard to re-install and haven't done so yet as I don't want to force it.
    Thinking of cooling them down on an ice tray without causing any condensate.
    Or setting a heat lamp in front of the opening or both to expand clearances.
    Other than that I see no choice but to "tap" them back in with force.

    Anyone know if they are normally this tight of a fit?

    Thanks

  3. #3
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    Default Re: MT180HD HST Problem

    OK,
    I put things back together.
    Then pulled the neutral valve out completely as before I hadn't removed the casing.

    I've yet to see any real issue. Just a little normal wear marks that a 25 year old tractor would have.

    Quick question,
    given that the charge pump directly feeds the 3ph and then the fluid goes to the spin on filter.
    If you start up the tractor with the filter off, shouldn't oil come out of the line?

    The 3ph still works as it should but this doesn't make sense to me.
    A tractor with sliding gear instead of HST has the exact same lines and routing regarding the
    charge pump and 3ph.

    How can it work if there is no oil coming into the filter?
    The draw line to the pump comes from the trans-axle reservoir via the pick up screen.
    Then pump pressure line then goes directly into the 3ph under the seat.
    Then out to the filter. I'm scratching my head here.............

  4. #4
    Super Star Member IslandTractor's Avatar
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    2007 Kioti DK40se HST, Woods BH

    Default

    Sorry I cannot help but just wanted to say your diagnostic efforts are impressive. I don't know anyone who is expert on your particular tractor or even HST but you might PM JJ as he is a hydraulics guru.

    Keep going! Good luck.

  5. #5
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    Default Re: MT180HD HST Problem

    Thanks IT,

    A little more thought process before I get my hands dirty again.
    This is becoming a puzzle to me and other than the normal price tag of a inevitable failure,
    I like these type of issues.

    The oil in the filter is my biggest question right now. I think we've all changed the oil in a car.
    When you remove the filter a lot of oil runs out and the filter is full.
    As I stated, I ran the tractor for 2-3 seconds with no filter and no oil came out of the line.
    The filter itself is less than ? full when I remove it. How can this be considered normal?
    Based on the 3ph working fine, again this makes no sense.

    However on this tractor the filter is at the high-point of the line system.
    Perhaps the oil is bleeding out of the line upon engine shutdown.
    I don't want to run it too long without a filter, so did not try to raise the lift while testing.
    Don't think I want too.......


    -mt180hd-trans-jpg

    Here's a picture of the HST. You can see the canister filter, a thumb screw cap and a big square plug.
    The thumb screw is where you check the reservoir oil level. The big square plug is where the swash plate
    moves back and forth.
    Here's a simple question for anyone with an HST...... should I be able to remove the top plug to watch the plate
    move back and forth while the engine is running, without oil spraying all over the place?
    I ask because I can. It almost acts as if the motor\pump is starving for oil, but I can see oil circulating
    and it is not frothy or foamy or full of air bubbles.

    One positive here is that after I took all the valves out and replaced them, with engine running I now can "feel"
    power being applied to the control shaft as I move it back and forth. It actually snaps to it's limits as
    soon as it moves off neutral.
    The negative is that even after ten minutes of warming the engine I can't get the tires to turn at all.
    At least when I started, with the tractor on stands, I could get things to move after letting it warm up for a few minutes.

    The frustration continues............
    Rick


    PS. I know I really need to check pressure, but I still haven't found any fittings.

  6. #6
    Super Star Member IslandTractor's Avatar
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    2007 Kioti DK40se HST, Woods BH

    Default

    I'm guessing that if you could get an experienced HST mechanic to read your posts that they could already give you a pretty good idea of what is wrong or at least what the next logical test should be. I also bet they want pressures.

    Regarding fittings, I presume they are metric which shouldn't be that hard to find these days. Do you have a local hydraulic shop?

  7. #7
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    Default Re: MT180HD HST Problem

    Sometimes you have to take a step back and laugh.

    I took off a guard around the spin-on oil filter and found that the lines I was following
    crossed under the cover.While it didn't give any better results, it cleared some things up.

    The oil filter is fed by the "charged output" port of the HST. After the filter oil flows to the cooler
    and then back into the HST. This external filter in no way affects the 3PH or the charge pump lines.
    The oil that goes to the 3PH returns to the reservoir somewhere internal to the assembly.
    This explains why the 3PH works even though there appears to be no oil in the filter.

    I ran the engine with it in gear and the big plug removed. I then poured oil into the hole and
    the wheels started to turn.
    This pretty much proves that the pump(HST motor) is starved for oil.
    Whether it's because of a valve or an internal piston/seal issue is yet to be resolved.

    But I'm very confident that it's not the charge pump.
    Of course I've been wrong before.
    Just ask my wife. LOL

  8. #8
    Super Star Member IslandTractor's Avatar
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    Default Re: MT180HD HST Problem

    Warning: naive suggestion ahead.

    If you have checked the hydraulic oil level and it is OK but the pump seems starved for oil, then there must be a blockage between the reservoir and pump. No? What would happen to the oil level if you simply kept adding oil to the pump as needed to turn the wheels? Presumably it will return to the reservoir and that oil level will rise. If that is the case then what other than a simple tube feeds the HST pump? Could a metal tube have been banged on a stump and kinked? Is the tube between the reservoir and pump visible for inspection?

    Now I'll repeat an earlier and better suggestion: send a note to JJ via the private message function of this site. JJ is a real experienced hydraulic guy and is always eager to help. Just point him to this thread. (go to "my home" then on the left side is my messages and you can send a message from there. JJ is all you need to put in the address).

  9. #9
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    Default Re: MT180HD HST Problem

    I'll pm JJ .

    The HST pump sends oil back to the reservoir only when it has enough pressure to turn the wheels.
    The HST is fed via the suction side of the charge pump, which is working fine.
    So any extra oil is simply picked up by the charge pump when HST has no demand for oil.
    This system prevents either pump from running dry, and prevents the HST from
    sending high pressure backwards in the system flow.
    No damage to oil lines. I went through them all made sure nothing was plugged or leaking.

    I ran it last night for 15 minutes. HST got hot. Neutral valve plugs got hot.
    High pressure relief valves only got warm through induction.
    Charged oil output from HST to oil filter and oil cooler stayed cold.

    I don't know your hobbies, but now that I'm seeing the way this works more clearly,
    it is exactly the way a tank-less water heater or hot water heating system with
    a primary loop and zoned circulating pumps is set up. One pump just pushes water through the heat exchanger in a loop,
    and the zones pull water from the loop as needed based on the individual room thermostats.

    Exact same idea here. The charge pump runs a primary loop through the 3PH back to reservoir.
    This flows constant while the engine is running. Then the HST pulls oil from this loop only when
    you activate the swash plate to engage the drive. When the tractor is not moving,
    the oil in the HST stays in the HST "zone" which includes the oil filter. This "zone" is not working.

    The HST pump/motor simply isn't moving any fluid. It's gotta come out.
    Just not sure what to look for inside. Never had one apart.
    Start out looking for metal flakes and torn seals I guess. There are two "relief valves" inside that are not
    accessible from the outside. Maybe one of those is bad.
    It will be Monday before I can split the frame. Perhaps JJ can chime in before then.

    Thanks again for your input.
    Rick
    Last edited by mt180; 07-19-2012 at 10:48 PM.

  10. #10
    Elite Member
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    Default Re: MT180HD HST Problem

    Not familiar with your exact model of HST but fairly familiar with HST tranny operation in general.

    Can you actually see the rotating group in your HST? If yes are you looking at the motor or the pump portion? If the motor and it is turning your HST is operating. If the pump and the motor is not turning you have problems.

    The HST itself is a closed loop system. The oil goes from the pump to the motor and returns from motor to the pump. The charge pump supplies flow to make up for losses in the HST drive system. How this works on most HST's is the charge pressure is regulated to some low pressure between 150 and 350 PSI. This low pressure oil is directed to the low pressure side of the HST circuit via check valves or a hot-oil-shuttle. The low pressure side of the HST changes depending on direction of travel. I.e. forward or reverse.

    Your charge pump I suspect is independent of the 3PH. kubota BX models have a priority flow control that supplies flow to the steering circuit which also is used for charge flow. These priority flow controls have been known to fail which trashes the HST.

    Some HST's have a built in charge pump.

    Not sure what the filter does in the picture you posted. if no oil comes out it does not sound good.

    Without the charge working your HST will be junk in a short time from cavitation. Cavitation will destroy your HST in a short time.

    If oil cooler line is staying cold your charge and or cooling pump is not working.

    With out a hydraulic schematic or some pressure reading I am only able to guess at your problem.

    Roy
    Artificial Intelligence will never overcome natural stupidity.

    Branson 2400H MMM & FEL

    JD 112

    BX1850 gone but not forgotten

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