Hydraulic problems Power Trac 1850

[PowerT1850]

Hi,
I am from Sweden and a new user on this forum. Have hydraulic problems. It run slow when I bought it and I have repaired one wheel engine and tested.
Should move some gravel when it stopped with a "jumping pedal". Not moving forward or backwards. The lifting and steering works but not so strong and a little slow to. I think it is a PT 1850 early modell and have a Kubota 4-cyl engine. Can not se what the mainpump have for brand or modell. Anyone that can tell?
See pictures. Need also the circuit for hydraulic to trubleshot.What can be wrong?
I am in a hurry because the snow is falling and I have nothing to move it with!!

 

[J_J]

You should check some pressure with a hyd gage and see if there is a loss somewhere.

I also have one of the older Power-tracs, with a Ford Industrial 45 HP gas engine.

I have never seen or heard about a PT with a Kubota in it.

Anyway, my PT has three pumps, the large pump is a variable speed hyd pump, and a piggyback pump is on the back of that pump for the PTO.

My steering and lift is from a pump driven by the fan belt.

There are some members that have 1850, but not that old.

Perhaps call Terry at Power-Trac and tell him what you have and they might have a parts manual.

http://www.power-trac.com/

 

[PowerT1850]

Hi JJ,
Thanks for quick reply. I have spoken to Terry last week and send several pictures. He should see if he could help me, but no answer.
I will take more pictures and more questions will come on this forum.

PowerT1850

 

[J_J]

I have referred your post to other members that have an 1850.

http://www.tractorbynet.com/forums/power-trac/

 

[ponytug]

I don't have your model, so it is a little difficult to diagnose, but it sounds like your tram pump (Variable Volume Pump) has an issue. That would be the leftmost pump in the series on the right photo. Hydraulic feedback at the pedal is not normal.

I am sorry not to have specific suggestions.

All the best,

Peter

Hi,
I am from Sweden and a new user on this forum. Have hydraulic problems. It run slow when I bought it and I have repaired one wheel engine and tested.
Should move some gravel when it stopped with a "jumping pedal". Not moving forward or backwards. The lifting and steering works but not so strong and a little slow to. I think it is a PT 1850 early modell and have a Kubota 4-cyl engine. Can not se what the mainpump have for brand or modell. Anyone that can tell?
See pictures. Need also the circuit for hydraulic to trubleshot.What can be wrong?
I am in a hurry because the snow is falling and I have nothing to move it with!!
View attachment 291351View attachment 291352View attachment 291353

 

[J_J]

Have you changed filters?

The charge pump pressure has to be correct also, and should be pumping about 10 percent of VSP pump volume .


Relief valves in the pump might be fouled.

Perhaps the trouble is in the wheel motor circuit.

I believe the wheel motors are in a series /parallel configuration.

If that is true, I believe the 3000+ psi high pressure is developed across two of the 1500 psi motors.

 

[wdchyd]

First thing I'd do is lift the tractor off the ground and see if both wheel motors are going in the same direction.....if not, then the drive motors are fighting themselves and timing is wrong internally in the repaired drive motor or the motor hoses are on backwards, or the motor work was done wrong

If not, then I'd remove that hydrostat pump and look at the internals for obvious problems

Either way it is always best to elevate the drive wheels when doing repairs to hydrostat systems for your own safety......these things sometimes have minds of their own....

 

[PowerT1850]

First thing I'd do is lift the tractor off the ground and see if both wheel motors are going in the same direction.....if not, then the drive motors are fighting themselves and timing is wrong internally in the repaired drive motor or the motor hoses are on backwards, or the motor work was done wrong

If not, then I'd remove that hydrostat pump and look at the internals for obvious problems

Either way it is always best to elevate the drive wheels when doing repairs to hydrostat systems for your own safety......these things sometimes have minds of their own....

Thanks for troubleshooting help. I will test to lift and see if it moves. It worked at first and then suddenly stopped, so connection is not backwards. The back and forward drive is working with electrical valves. Maybe this is something wrong with?
See attach images. Is the small pump at right side on Kubota engine a hydraulic pump for steering. Is the dualpump with axial pistons nearest engine ( drive ) and gearwheel back ( for lifting and tilt ). Anyone that can tell what brand / modell. Hard to get spareparts otherwise. The mainpump, is it difficult to repair? Expensive?
Buy a new? I am not skilled at hydraulic, but work as a tool engineer and have worked a lot with engines, in particular with chevy smallblocks.

// PowerT1850

 

[J_J]

Your machine has a serial number and Terry should be able to tell you how old it is.

Ask the parts guy for a parts list.

I would wipe and clean the pumps, and use a mirror or put the camera under the pump and take a picture.

The numbers on my pump were on the bottom.

The pump on the rear of my tram pump is the PTO pump.

Where is your third pump located?

You should be able to make up a hyd schematic by following all the hoses from point to point.

Go to your PTO connections and follow the hoses back to the pump supplying the hyd fluid. The valve controlling speed on the PTO on my early 90's machine is a lever valve.

Are you using 10W-40 motor oil in the hyd tank, or synthetic

Motor oil is the recommended fluid for hyd systems.

 

[SpringHollow]

That looks very different from my PT 1850. Some of the older models did have a Kubota engine. Terry really should be able to help but they do not seem to use email much. I sent you a PM.

It helps to rig up a pressure gauge to a Tee and some adapters to put it into various places in the circuits to see what is happening. It is really hard to get JJ to do that - he hates having people measure the pressures in their systems. (just kidding - it is one of the things he always recommends and he did so here. Because of him, I bought gauges to let me do that and a flow meter that was going cheap).

Wish I could help more.

Ken

 

[wdchyd]

Not sure what the model of pump it is but it looks similar to an oil-gear piston pump, old style with swash-plate over-center design (used in closed circuit hydrostat systems)

It looks like a tennant sweeper pump I worked on a few years ago, If it is then you may have had trouble with contaminates from the drive motor repair spoil your pump....it is always best when you have drive motor issues to remove and clean, lap, reseal and reassemble pumps along with new oil and filters when doing any repairs in that drive circuit

By the sounds of it the charge pump may have locked up or your rotation group/swash plates in the pump may have failed.....or the original parts that failed in the drive motor are still floating around

If I see it correctly, the front pump design you have is a variable piston pump with over-center swash plate (connected to the lever) to give you forward and backward motion for the drive motors

 

[wdchyd]

The back and forward drive is working with electrical valves. Maybe this is something wrong with?


// PowerT1850

Oooo, Sorry i missed that......having a solenoid valve changes everything...is the output of the pump going into the inlet of the solenoid valve base??...maybe the variable pump is changing it's direction thru the solenoid....if that's the case then there should be a manual override on the end of the solenoid coils......best to try those overides while the drive wheels are off the ground

 

[wdchyd]

also, another tip......to check if the solenoid coil is electrified, use the steel blade of a pocket knife (one that a magnet will stick) and touch the end of the solenoid coil to feel the magnetism when engaged, if the coil is energized your feel it

This will not show if the valve stem is stuck in the housing, but the manual overide push pin (if it has one in the center of the solenoid coil area) may clear the condition if it is stuck.........the valve stem should be spring centered when not engaged electrically

 

[PowerT1850]

Thanks for helping me! Nice PT1850 you have Ken. Hope mine will be like this someday. I have now clean the pump as JJ told and there have been a identificaton plate at the right side. But now it is gone! Hope that Terry should answer my mails, but no success. Does he have terry@power-trac.com or have I got this wrong? I also have sent to info@power-trac.com. If I donｴt know what pump there is I think it will be hard to repair. JJ No have not three pumps, it is one dualpump and one little at the right side of engine ( Think this is the steering). I will try to make my own hyd scheme by follow hoses.
What part shall I use if/when I replace motors and pump? Maybe this ??? Surplus Center - 28.3 cu in HYD WHEEL MOTOR W/5 BOLT HUB

PT1850

 

[J_J]

Your task is not going to be an easy one as like me, I have very little documentation on my machine. My PT-1445 is an early 90's machine without the Quick Attach setup, and the only large gas engine that I know of.

You need all things working to take a reference value for pressure, etc.

For instance, if the pressure from the pump is capable of 3000 psi, and the flow is passing through two 15 cu in wheel motors in series, that means that each one of the motors is developing 1500 psi, so if you are going to replace a single motor, you have to get the same cu in motor and the correct psi wheel motor.

As with with most things, you have to know how something works to fully analyze and diagnose a problem.

Based on on what you have, some of the unknown factors can be computed, such as HP to power a pump, how much torque is needed for a motor to turn a wheel.

I now know most of the details of my PT by hands on operation, and replacing parts .

Your variable displacement pump could be made by Eaton, Char-Lyn. Wheel motors by White, Sauer-Danfoss, etc.

If you use the wrong wheel motor, your torque could be cut in half.

I think I would install a tee with a 1/4 male QD in each hyd circuit so you can plug in a 3000 psi liquid filled hyd gage and analyze the results.

When things are broke, there is very little or no reference.

Here are some pics of some hyd test sets. Should cost about $30 US

The size of the pump should be matched to the wheel motors.

Have you read through some of the Power-Trac forum post. They go way back. You can search for 1850 and maybe pick up some useful data.

Don't know the reasoning, but the people at Power-Trac do not participate in the PT forums.

If you can get a hold of Terry, he will talk to you.

Sometimes you have to drag data out of the PT folks.

The engine is the most expensive item on the PT, and then the Variable Displacement pump.

 

[wdchyd]

..............................maybe the variable pump is changing it's direction thru the solenoid........

Or maybe they are using the solenoid for "High/Low" selection.... and it's still an over-center swash plate for forward/rev..??

it all depends how it's plumbed...(motors in series for high speed vs motors in parallel for low speed)...:confused3:

 

[PowerT1850]

Hi,
Looked at the solenoids. You are right! The magnetic power workes but they seems to be stuck, have removed the colils and iron unit to make them move again. It is the solenoids that switch forwar/rev. If this dosn´t help I will lift the lid under the "speed control arm" and have a look!

PowerT1850

 

[SpringHollow]

My PTO solenoid valve has stuck several times. I was told that it was not repairable but I tore it apart each time, freed it up and reinstalled it. They were expensive so it made sense to try. Each time, they lasted for about 2 years before needing to be cleaned again. I think the main problem with mine is that 9 months can go by without using the main PTO and so the valve does not get cycled.

PTO Solenoid Repair

Ken

 

[wdchyd]

PowerT,

if the valve spool is stuck, then it's either contaminates in the oil or a burr that develops from the "Slam/Slam" when shifting....

The spools can be cleaned and checked for no hang-ups........the spool should not bind and should self-center with the internal springs

Worse case senario, those valves are easy to find replacements but SpringHollow has it right......clean it

Did you see the manual override on the ends (they may be rusted tight), that's the quickest way to free it without removing the valve

I would proceed with caution if you decide to take the cover/arm off that pump, If needed the best would be to remove the whole pump if you are going on a fishing expedition on it

 

[PowerT1850]

I have removed the pump. It was just the manual overrides that was stuck on solenoids, the electrical function is ok. I really need to know the brand of this pump ( Se picture ). Is it a good idea to have a look myself inside this or let a profesionall gay handle it?.