Hello all new to the forum. I have read several post on similar issues. None I feel are quite the same. Just looking for some good advice. Problem is left side does not wanna go forward has low power. It goes fine in reverse. I have cleaned both office in the tandem pump. I have swapped relief valves and even swapped the spools. Nothing changed I have read on here about swapping lines to the drive motors. I have not done this however for fear of contaminating the other side. I did however swap hoses in the left motor. All this did was reverse left side controls. Does this indicate that left side motor is good and tandem pump is bad?
If you swapped the hoses on the left motor and it still did not want to go forward - that seems to indicates that it's is the left drive motor and not the pump.
Pressure checks would be in order. Just the charge pressure at standby and during drive will tell most everything you need to know.
Thanks Phil 314 I was hopping it was the motor and not the pump due to $$. Motor was strong in reverse so I was fearing the worst that it was the pump. If I rebuild the motor and flush lines and drain and fill hydraulic tank with new filter would it be ok if it’s just seals leaking in motor? Thanks vetech63 I checked charge pressure it was low I shimmed charge relief valve with some washers to get it up to spec. I also hooked gauge to left side forward port pressure is good until I push left control lever then pressure drops to like 1000 psi. Also when I hold left lever forward I lose right side. Obviously a major pressure leak just wanted to pick ur all brains if u thought motor or tandem pump. I just an ol farm boy trying to make it on ol junk The owner showed a receipt where he had case put in a rebuilt pump but said it still wasn’t right
Hook up your charge pressure gauge and record the pressure in neutral at high engine idle. With the engine still at high idle, stroke each lever individually forward and reverse and record those readings of the charge pressure gauge. Im thinking charge pressure is between 200-300 psi on average. It shouldn't drop any or barely at full stroke on each lever in each direction
I did manual says 390 to 415 it was like 300 I shimmed the relief valve with washers got pressure up to about 400 pressure stayed constant when I hit levers very little movement in gauge. Hooked gauge to left side forward port on tandem pump would be like 4500 as soon as I hit forward pressure would be like 1000 then recover quickly once I let off
A little clarification. You swapped the lines going to the drive motor on the side that has this problem and now it drives good forward but not reverse? Or does it still drive good in reverse? Just trying to be 199% sure I'm following the description.
Yes I swapped lines on drive side that was weak only. When I did it just swapped the controls. When I pushed forward on lever it would go in reverse fine. When I pulled back on left lever it would creep forward but just weak. I am kind of hesitant to swap lines to both motors for fear of bringing contamination to the right side and doubling the work load and cost thanks for replying
This doesn't sound like a motor problem. Have you checked the reliefs on the pump for that side? There should be 1 for forward and another for reverse. You could swap them and see if the problem moves
Yes I did swap the reliefs condition stayed the same. I have gauge hooked to the left forward drive port. I am getting 4500 psi which I assume means the pump is good as soon as I hit lever forward pressure drops to around 1000. Could press be leaking off in drive motor which I feel would be odd because reverse works fine.
Some drive motors have a shuttle valve. Im not sure about yours. Something isn't making sense here
I might be wrong, double check my logic here. If the motor works in reverse in both cases (when the hose are normal & reverse) this would indicate that the pump is working in both directions. And since motor forward doesn't work in either case, then this would be a motor problem, not a pump problem. ???
Sounds like it to me too, but would have to dig into everything on the forward side of that motor including as Vetech says any valving in the system.
Take a pic of the pump and the drive motor and post them here. Your system should be a simple design because of the age of the machine. We can help you troubleshoot the problem but we need to see what type of system this is.
Thanks again for all the help and replies Here is sum pics if they not good enough I will take more just let me know. I was looking at seal kit for motor at L P S One had Teflon seals one didn’t are the Teflon seals that much better? The yellow plastic thing on the side of pump is cap for my gauge I still have hooked up in toward drive port
Some more pics thanks again
Looks like simple Danfoss gerotor hydraulic motors. The next test would be to remove both of the big hoses on the weak drive side motor and put your gauge in the end of each hose. The pump is a 2 way stroke so the oil will reverse direction depending on swash plate position. 1 hose will pressurized when stroked in one direction where the other is the return…switches direction when you stroke the other direction. You should see the same pressure going both directions but the pressure will switch to the other hose. 2 gauges would be better. The reliefs for both directions are in the pump……..1 for left side forward, 1 for left side reverse, 1 for right side forward, and 1 for right side reverse.
Just a tip as well, make sure to note the timing of the motor through the process that vetech has outlined above - which orifice gets pressurized based on the rotation of the shaft. This will be useful if you end up having to take the motor apart because it does have a standard timing. I had this exact motor apart earlier this year, it's quite simple, but I didn't check the timing before disassembly. Of course you can just swap the hoses if you don't know what to set the timing to but it's good to know.
Vetech63 thanks for the advice. Do I need to use a tee fitting for the gauge at the motor or can I just dead end the gauge on the line?
Dead head the gauge in the line to completely eliminate the drive motor
Thanks for following but I’m Having trouble adapting 3/4 jic to my gauges had to order fittings will report back as soon as I get them
Would it not be good to look at case drain flow before tearing the hyd system open, if you have a lot more case drain volume in one direction you could assume a motor issue , which I firmly believe it is.
How would perform this type of test? Take both lines of motor and place in clean equal buckets of oil then measure amount of oil in buckets? Do not have a flow meter. I could order one if needed. Any isolation of parts through troubleshooting would be time and money saved.
Keep on the track of ensuring you have adequate pressure and flow from the hydrostatic pump(s) before breaking into anything. Dead end two separate gauges into each pressure line from the pump, and stroke the pump fully each direction. Reset, or calibrate your pressure relief valves if necessary to correct values. If the pressures are correct, then look to measure flow but ensure you have pressure first. Vtech has you on the correct path for isolation, (IMO).
1693, yes Vtech is good as to his method and it will show up a pump problem, my thought processes say that a reversal of the charge reliefs and the reversal of the hoses as he has already done has simply moved the problem to the opposite lever position, also, loss of charge pressure when the lever is reversed would indicate a leak. It is possible that a charge check is not closing properly on system reversal, are they part of the high pressure relief or a separate piece? I will have to go to the online parts site and explore that, at any rate with a good hydraulic shop adapting the JICs down to 1/4 mp should not be a problem. To answer his question as to my suggestion Taking the small drain line off and substituting a hose which could be put in a 5 gallon bucket a bad motor leakage in one direction would show as a drastically increased amount of case drain flow in the defective direction. This would be done without disconnect of the whole system
Correct on all counts and I'm certainly not disagreeing on anything. However there are several ideas being floated with this scenario at once and the problem needs "drilled down" or isolated into a single problem area. I don't get the feeling the OP is really experienced in hydraulics and their operation, so don't want to see him on a wayward or meandering path that may be incorrect. No worries and certainly no offense of any type meant.
Yes, We are dealing with people who have no idea how a closed loop system works, that is a thing I try to keep in mind, not everyone has the advantage of 50+ years of hydraulic oil up their arm pits, I think that people like ourselves tend to follow our gut because we have done so much of it and it is kinda second nature. BTW, the charge checks are not shown as a separate item in the pump breakdown so I must assume their function would be contained within the high pressure relief. Certainly a high pressure deadhead both lines will be telling, no offence taken, I have been right sometimes and dead wrong others. Part of the game!
Yes, I've been wrong plenty also. I'm not a hydraulics whiz by any stretch, but surely know enough to get into trouble.....
Got gauge hooked up to lines at motor today and did some testing. Like vetech63 suggested and Low and behold I got 4500psi on both lines!! Assuming that it’s just the drive motor that is bad. I was so happy I felt like I just won the hillbilly lottery the readings were kind of different in respect of how they got there though. When gauge was hooked to the reverse line with the motor fitting capped it had 0 psi at idle when I barely touched the lever in reverse it went to 3000 psi pulled a little more it went to 4500 psi. Looked good I assume. Next I took forward line off (the one with the trouble) capped both motor fittings and reverse line hooked up gauge (I sent u guys a pic of all the fittings I had to rig up figured u might get a chuckle) the forward pressure was 1000 psi at idle and when I pushed lever it went straight to 4500 psi there was no 3000 psi when I barely pushed on the lever like reverse did could be a fluke I did have slight leakage on gauge conglomeration when checking reverse. Was wanting to get u guys opinion on is it safe to say motor is bad? Is there anything else I should check? Any tips on removing motor? Do I need to slide cab forward? How hard are they to rebuild? Was going to order seal and o ring kit from LPS and attempt myself. Thanks for all the help and good info Sorry for length post and all the questions will post more pics and updates through this process to help others.
If you don't have the service manual, you can download here---> https://cdn.minnpar.com/partbooks/c...ni Loader Service Parts Operators 3 in 1-.pdf
Thanks tinkerer I do have the service manual I followed their troubleshooting procedure. It said to much pressure loss disassemble the tandem pump and drive motor inspect for worn or damaged parts I was just trying to eliminate one or the other
Got sum time off from work slid cab forward gutted drive motor found sum metal shavings and wear rings on large plate the wear rings are not deep enough to catch a finger nail could I just polish them out? What would be best thing to use? Looks like retaining pin sheared and just got wore down # 24 and 25 The hole is kinda oblonged now is this drive motor salvageable? I also noticed an o ring was missing at the bottom of the large plate # 22. Leads me to wonder if someone else was in here before?
Here is a pic of some of the wear I would like to polish out. Also pic of oblonged hole where retaining pin sat. What would cause it to break any ideas?
If it were me, (and it's not) I'd get a reman motor and not guess. Hopefully the balance of the system is not compromised from metal filings circulating through. Regardless, when the system is back together a thorough flush is in order to trap any contaminants.
Yes worried about tandem pump now