MT180HD HST Problem

[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 ?