MT180HD HST Problem

[mt180]

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.

 

[mt180]

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

 

[mt180]

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.............

 

[IslandTractor]

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.

 

[mt180]

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.......




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.

 

[IslandTractor]

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?

 

[mt180]

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

 

[IslandTractor]

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).

 

[mt180]

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

 

[oldnslo]

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

 

[mt180]

oldnslo,

Thank you for the reply.
I'm attaching some pics I hope you can see them in large format.
They will show a label side to side image.
A system schematic, and an oil line routing.


Yes the HST is a closed loop system.
The 3PH is also a closed system, however they share the same reservoir and charge pump.
The oil line routing for the 3PH is exactly the same for the gear type unit as the HST.

Adding HST includes charged lines to the oil filter and the oil cooler.
The HST oil pickup is a shared line with the charge pump.

When I look into the square plug (#22) on the HST I see the piston retainer and pistons
as well as the swash plate.
I can only see the pistons with the plate in the reverse position.
The assembly does rotate, there is oil inside, and it is not foamy when running.
No oil returns to the reservoir unless the system activates and turns the wheels.

Oil lines #18, #19, #20 are the charged oil output to filter and cooler.
For whatever reason they are not shown on the oil line routing page of the manual.
I do not believe there is any oil flowing through them unless the wheels are turning.
I cannot confirm that as I can't keep them engaged long enough.

There is an internal check valve I cannot test to prevent high pressure oil entering the charge pump.
I have taken out and inspected the neutral valve, low pressure and high pressure valves as per manual.
I found no foreign matter. The only irregularity is that the manual states to insert a bolt into the high
pressure valve to assist removal. A picture references using ones hand to pull the valve casing out.
I cannot do this. I need to use a lever on the bolt to remove them.
I also have to apply a fair amount of force to re-install them. However I see no obvious score lines
or indication of why. Perhaps the manual is simplifying things?

It just seems like the HST pump/motor isn't getting oil, or isn't pulling oil from the charge line.

I will say that after inspecting the valves I have only gotten the wheels to turn once.
Before at least I could get them to move once in a while.
Although now when moving the swash plate from neutral to either forward or reverse,
there is a feeling of power in the control arm. When activating the shaft it
snaps to the forward extreme and gives resistance to move back to neutral.
Reverse acts the same way, neither position wants to return to neutral.

Thank you for your time and any thoughts.

 

[oldnslo]

First: The HST charge pump is separate from the main pump and not part of the 3PH. Look at the post of right side and left side views You will see the lines to & from oil cooler. These are the charge pump circuit. On the page labeled Hydraulic system it shows the pressure line from the oil pump running parallel to the cooler line and using the same hold down clamp. This is your 3PH and or auxiliary valve oil supply.


Diagnostic steps based on the schematic posted:

I suspect the HST charge pump is built into the HST pump. This is a common practice on some HST models.

Per the schematic: The charge pump flow goes through the oil cooler, then the filter and then to the check valves (item 5). These check valves direct the oil to the low pressure side of the HST. Item 12 the low pressure relief controls the charge pressure.

Things I would check if possible:
1) Can you access the inlet screen/ strainer for the charge pump. I would guess it may be under item 16. I would suspect you will have to drain the oil to check this. If gutsy or stupid like me, remove line 24 and see if oil comes out freely from item 16. No or slow oil flow would indicate the screen/strainer is plugged. Once you are 100% sure this line is open go to step 2.

2) Do you get oil of the line on the right side of the tractor going to the oil cooler? Remove this line and point it into a bucket. Crank the tractor over for a few seconds to a minute max. Do not see any item numbers for this line. If you get oil flow out of this line go to step three. Reinstall this line and go to step three.

3) remove the outlet line from the cooler (item 25) and place it in the bucket. Operate the tractor again. Do you get flow out of this line? If no the cooler is plugged and blocking the flow. If yes reconnect this line and go to step 4.

4) Remove the oil filter inlet line (item 23) and point it into the bucket. Run the tractor again. Do you get oil out of this line? If no the oil path is blocked in the tranny housing between the cooler return line and the filter inlet line. If yes you will need to obtain a pressure gauge and some fittings so that you can take some pressure readings.

Pressure reading would be need to be taken if possible between the filter and the check valves (item 5) Low or no pressure here would indicate a faulty charge system or a badly worn HST pump or motor or both.

The schematic shows the "neutral valve" as what I believe is a "hot-oil-shuttle" valve. The purpose of the "hot-oil-shuttle" is to dump the excess charge flow from the low pressure side of the HST main circuit at a lower pressure than the low pressure relief (item 2). This keeps a constant flow of cooling oil in the HST and also aids in flushing contaminates from the HST.

You state the swash plate wants to go to max speed which is the exact opposite of how it should operate. This indicates there is no pressure to the motor which may be an indication the motor is worn badly. Bad news is that typically if either the pump or motor goes bad it destroys both since they are closed loop with no filtration in that loop.

Hope this helps

Roy

 

[IslandTractor]

Great post Roy. Over my head but it is clear you know what you are talking about and you communicate very clearly and precisely.

 

[oldnslo]

Great post Roy. Over my head but it is clear you know what you are talking about and you communicate very clearly and precisely.

thanks island tractor,
I have received some good advice and help from members and I am just trying to pass this along.

I am concerned that the HST on MT180's tractor is shot but the only way to tell over the internet is the process of elimination. Most people simply do not have fittings and pressure gauges or flow meters to do diagnostic work so the old fashioned fill a bucket is almost always some thing a person can do.

Roy

 

[mt180]

oldnslo,
thank you for the time and your reply.
I see now where my mistakes began. The manual which is clearly a foreign writing translated into English,
calls things by several different names throughout.
The "oil pump" or "main pump" that is driven by the engine is also called the "charge pump" in some sections.

Until I re-read your post, and then looked closer at the exploded view, I didn't realize that the real charge pump is in fact inside that HST assembly.

I have a 5000psi guage set but have not made finding fittings a priority.
I'm 95% done with the removal process. Several conclusions led me to take this route rather than further
guessing and assumptions.

1) wire mesh filter in reservoir is clean and particle free.
2) all oil lines and the cooler are clear and open.
3) I ran the engine with low pressure relief valve removed, no oil came out.
4) I ran the engine with neutral valve assembly out, no oil came out.
5) As no oil is coming out of the charged output line, the oil filter is not being filled.

Conclusion.......
The internal charge pump is not pulling in oil and therefore is not providing motor with fluid.
Either because of failure or obstruction of pump or check valves.

Now I'm having trouble separating the unit from the transaxle. That oem sealant is tough stuff.
I'm on vacation next week, so all I want to do is get it on the bench before then.
Then I'll crack it open when I get back.

At this point I'm more than happy to take in any advice on what to look for inside
besides total failure of seals and visual scoring etc.
I'm also at a loss of where to begin looking for a rebuild kit, if there even is one available.

I know Case-IH sold this exact tractor as a model number 234 or 235.
However there isn't a dealer near me, and without high speed internet, it takes forever
to load there parts locator site.

thanks again for your shared knowledge.
I'm one of those guys that knows enough about stuff to get into trouble, but not always enough
to get out of it.
Diagnosis is not my strong suit.
That's why I got out of the auto repair industry 25 years ago.
I really enjoyed it, but things were getting too "electronic" for me. Even back then.
Not to mention the cost of testing equipment.
I much prefer the R&R mechanical side of things.
Rick

 

[oldnslo]

Where to get parts? Not sure myself since Case in now New Holland.

What to look for:
1) Is the charge pump broken or the drive shaft not turning? Best guess is the charge pump is Geroter style where there is a lobed gear that spins an external cam ring. Cam ring scored, gear scored, wear faces scored, etc. These are similar to the oil pumps used on Briggs OHV motors and possibly even some car engines. These are usually pretty tough units but anything can fail.

2) Scoring on the faces of the cylinder blocks and mating sufaces. If the charge has failed i would expect to see cavition damage which looks like these surfaces have been sand blasted.

3) if the pump and motor rotating group have slippers on the pistons, are the edges of the slippers rolled and worn? Is there scratches or gouges on the faces of the pistons.

4) Is the swash plate wear the piston slippers run worn or scored?

If you have questions about components and have the ability post some pictures, they are worth a 1000 words.

These would be the main wear components in a HST.

Agree, give me mechanical components Vs chasing electrons in a circuit board.

Where in Wisconsin are you located?

Above all, keep everything extremely clean on reassembly.

 

[mt180]

Thanks again,
Will tear into it after a much needed vacation.
After this project is finished its back to the Gravely arsenal.

I'm just west of Port Washington.
Which is about 20 miles north of Milwaukee.
Rick

 

[mt180]

Well,
It's official the charge pump blew up.
Vane cracked and rotor was in about 8 pieces.
Problem is I can't find about 30% of it.
I don't see any unreasonable scoring on anything.
Swash plate looks good as did all the pistons I looked at.
I didn't find any pieces in the transaxle or inside the HST unit.

I'm not sure what the hardness is of the various parts inside.
Is it possible that the pieces just disintegrated?

Looking for parts now. Would it be ok to just replace the vane and rotor?
Or if the housing is also needed to be replaced.

 

[mt180]

Having trouble finding parts.
If anyone can help I would appreciate it.
Are Satoh Beavers still being supported?

 

[oliver28472]

Have you checked with Valley Power and Sheaffer's Town & Country Tractor ?