That one also variable displacement pump but it does show main relief and pilot circuit relief, Ronray’s shows only pilot circuit relief. And this diagram is more correct.
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Boom lift Drive Wheels torque fade
- Thread starter Ronray
- Start date
TVA, I think the main relief valve on my 1981 hydraulic schematic is at the opposite end of the proportional valve bank from where it shows on Bus 1986 schematic. But I still do not see the main relief valve on either hose kit diagram? So I am wondering if the main relief valve is built in 2 the cast iron proportional valve bank manifold, instead of being a separate small aluminum valve bank manifold?
Okay, so I found what may be a pressure relief valve adjusting screw and lock nut on the right end of my proportional valve Bank manifold just below the large exit hose, and also corresponding to the location on the hydraulic schematic for my my 1980 machine. And if that is what it is, it looks like the adjusting screw is almost all the way in and even with the lock nut. Your thoughts?
TVA, you also asked me to photograph the ID tags on the proportional valves. The first photo is the yellow tag on the drive function valve and looks to have a PSI rating 500 lb. The other three functions have a black tag with a PSI rating of 400 lb. Would this be the PSI required from the pilot line? I also noticed in my manual somewhere that the pilot PSI could be adjusted up to 350 lb. Mine currently hovers between 100 and 200 lb.
Those are tags from solenoids, I need the tag off of Main control valve housings. I want to try and find the pressure regulator on section illustration for you. And yes - your pilot circuit should not exceed 400 psi, that’s why you have pilot circuit relief, the one you have found.
Thanks TVA! This 1980 proportional valve Bank manifold of mine does look pretty different then the 1986 one showing in the picture posted by Bus.
I will keep you posted on the results of testing with the 2 speed cylinder hoses blocked. Thanks!
I will keep you posted on the results of testing with the 2 speed cylinder hoses blocked. Thanks!
bus-junkie
Member
Here's where I'm at with this Marklift 62. All functions except "drive" work as I feel they should. I have movement in the "low" range that is consistent now from a few minutes after cold-start until 30 minutes or so after (that's as long as I've run it). It would always fail minutes after cold-start meaning forward or reverse movement would be gone. "High" range will move the machine only on completely flat ground at a rate that is faster than "low". I can climb up what I believe is 8 degrees or so (that's all I have for a hill to try it on) in low range. I can block the drive wheels with a 2 X 4 and it will crawl over them. If I block them with a 4 X 4, it will try and try and once in a while get over them too. Is this "normal" performance for these manlifts? I'll try to post a video of the vent oil off the wheel motors also showing that the pressure is at 2100 lbs. while doing this.
bus-junkie
Member
Here is a link to a video showing the vent-oil off the two wheel motors of a Marklift 62. The left motor seems to exhaust/vent more but after a bit the right one will produce more. After the test the two buckets held the same amount. During this test both the gauge on the main of the proportioning valve body and the gauge here in the picture at the control block top off at 2100 psi. I had the machine trigged with a 4 X 4 block in front of each drive wheel.
Great video bus. Yes I had the same test results with the wheel motor vent lines. But I am curious that now you are getting 2100 lb to the gauge on the wheel Motors whereas before you were only getting 1400 pounds. Recall that I was getting 1,200 lb to the wheel motor gauge when wheel Motors engaged.
I have not yet had the time to try this, but this was suggested by TVA:
Disconnect and plug both of the hydraulic lines going to your high-speed cylinder, in your case, you have a high speed shift cylinder next to each wheel , which could indicate a possible leak of oil inside the cylinder seals. And see if that kicks up the pressure to your wheel Motors, which TVA previously suggested should be around 3,000 pounds. Also FYI, I recall seeing in the manual under troubleshooting low torque to the wheels that you should test the pressure with a 3000 pound gauge. While the manual did not actually say that the flow pressure should be at 3,000 lb, I can only assume that because they recommended a 3000 pound gauge that that should be the pressure like TVA said. And you should also unplug the wire to the 2 Speed Shift cylinder solenoid on the mini valve Bank.
If this does not kick up the pressure, TVA suggested just taking a pressure reading on a wheel motor line with the function engaged but all 4 wheel motor lines plugged after the gauge. If you got three thousand pounds or significantly higher, then this would indicate no leaks within the system before the wheel Motors, and that the leakage was in the wheel Motors, if I understand the test proposed by TVA.
Did you have both of your wheel Motors rebuilt?
I have not yet had the time to try this, but this was suggested by TVA:
Disconnect and plug both of the hydraulic lines going to your high-speed cylinder, in your case, you have a high speed shift cylinder next to each wheel , which could indicate a possible leak of oil inside the cylinder seals. And see if that kicks up the pressure to your wheel Motors, which TVA previously suggested should be around 3,000 pounds. Also FYI, I recall seeing in the manual under troubleshooting low torque to the wheels that you should test the pressure with a 3000 pound gauge. While the manual did not actually say that the flow pressure should be at 3,000 lb, I can only assume that because they recommended a 3000 pound gauge that that should be the pressure like TVA said. And you should also unplug the wire to the 2 Speed Shift cylinder solenoid on the mini valve Bank.
If this does not kick up the pressure, TVA suggested just taking a pressure reading on a wheel motor line with the function engaged but all 4 wheel motor lines plugged after the gauge. If you got three thousand pounds or significantly higher, then this would indicate no leaks within the system before the wheel Motors, and that the leakage was in the wheel Motors, if I understand the test proposed by TVA.
Did you have both of your wheel Motors rebuilt?
bus-junkie
Member
You know Ron, with all I've done I lost track of the order in which I did things and the result of each. I may even have an intermittent problem. Right now it's better than it's been but I'm not convinced it's at it's potential. The manual and that I.D. plate on the rear of the machine both say that this unit is only going to produce 2500 psi. So unless we adjust the main pressure regulator we won't ever achieve 3000 lbs. I would think that if I could get the 2500 lbs. to show up at the wheel motors it would help even more. Maybe there is an adjustment for that. I think I had told you that I did have a problem with the cylinder on the right wheel motor and that the rod had come unthreaded from whatever piston is inside that cylinder. I never took the cylinder apart, I just put the rod back in the boot and felt around until I got it to screw back into the piston. Once it was in the 1/2" or so that was threaded on the end of the rod, I think the piston was turning because there was nothing to hold it so I couldn't get it 'real' tight. So, maybe with that rod unscrewed from the piston, oil could leak through from 'high' oil to 'low' oil and that would have lowered the pressure reading, just not sure...……..
I just got done checking and filling the planetaries, the left one was low. I had the torque-hub lock caps off to better get at the fill plug and two of the bolts didn't feel right. I put a tap in and broke it off below surface. After taking the next hub section off I'd found out that those two bolt holes had been heli-coiled in the past. My tap must have gotten snarled up on the wire coil and bound up. I burnt the tap center out with the torch, blew some pieces out with air and got hold of an end of the heli-coil and pulled the remaining thread out. I then chased the threads with the 1/4 X 20 heli-coil tap and installed two new heli-coils. She's good and back together now. The left rear tire was down to 50 lbs. and it's now up to 75 like the right side.
I had taken the right wheel motor off last fall and it spent most of the winter at the hydraulic shop as parts are not readily available. Mine are Cessna motors out of Italy. The tech that took it apart had said that it could use some seals and a bearing but it shouldn't have been the cause of the lack of movement. So when they got it done I put it back in and have been playing with the many other parts of the machine to get where I am now. Even rebuilt the carburetor on this old Wisconsin V-4.
I just got done checking and filling the planetaries, the left one was low. I had the torque-hub lock caps off to better get at the fill plug and two of the bolts didn't feel right. I put a tap in and broke it off below surface. After taking the next hub section off I'd found out that those two bolt holes had been heli-coiled in the past. My tap must have gotten snarled up on the wire coil and bound up. I burnt the tap center out with the torch, blew some pieces out with air and got hold of an end of the heli-coil and pulled the remaining thread out. I then chased the threads with the 1/4 X 20 heli-coil tap and installed two new heli-coils. She's good and back together now. The left rear tire was down to 50 lbs. and it's now up to 75 like the right side.
I had taken the right wheel motor off last fall and it spent most of the winter at the hydraulic shop as parts are not readily available. Mine are Cessna motors out of Italy. The tech that took it apart had said that it could use some seals and a bearing but it shouldn't have been the cause of the lack of movement. So when they got it done I put it back in and have been playing with the many other parts of the machine to get where I am now. Even rebuilt the carburetor on this old Wisconsin V-4.
Sorry guys - crazy busy lately!
You got to go with pressures listed in your specs! But most of machines I dealt with had them close to 3000psi. Like 2600,2700, 2900.
One thing to know: pressure is closest related to torque, and flow to speed. So if you have low torque then first thing you check is pressure, although low can be so low that there’s not enough of it to building up the decent pressure.
Case drain evaluation of the motor is only half of the deal, there’s condition exists which called “cross port leakage” and it will not show up on your case drain flow.
But if you have low pressure problem - you need to find out where you loosing it. I like to start at end user and go backwards. So I start by eliminating motors by plugging the hoses and see if pressure goes up.
If plugging motors didn’t give you results, then next big suspect will be center pivot, but there’s components in between. But you have to divide the system give your self direction.
I would say in excavators weak drive problems caused more by center pivot ( rotary manifold) then the travel motors.
You got to go with pressures listed in your specs! But most of machines I dealt with had them close to 3000psi. Like 2600,2700, 2900.
One thing to know: pressure is closest related to torque, and flow to speed. So if you have low torque then first thing you check is pressure, although low can be so low that there’s not enough of it to building up the decent pressure.
Case drain evaluation of the motor is only half of the deal, there’s condition exists which called “cross port leakage” and it will not show up on your case drain flow.
But if you have low pressure problem - you need to find out where you loosing it. I like to start at end user and go backwards. So I start by eliminating motors by plugging the hoses and see if pressure goes up.
If plugging motors didn’t give you results, then next big suspect will be center pivot, but there’s components in between. But you have to divide the system give your self direction.
I would say in excavators weak drive problems caused more by center pivot ( rotary manifold) then the travel motors.
Great advice TVA! Yes, I was also thinking possibly that rotary manifold. The problem is I don't see a way to get to that manifold without being underneath the machine?
I have been sidetracked with other projects lately, but my next step will be 2 plug off those hoses to the two speed shift cylinder and if that does not work, plug off the wheel motor hoses.
I'm also wondering if there might be some fluid leaking through the proportional valves for the other functions such as boom lift and extension and rotation? If there was even a little leakage, would that be enough to engage that function very slowly for example?
And kind of a dumb question since I haven't even tried it on the machine yet, but I'm wondering if you can engage two functions at the same time for example boom lift and extension or rotation, and if it just slows the function down when two of them operate at the same time?
I have been sidetracked with other projects lately, but my next step will be 2 plug off those hoses to the two speed shift cylinder and if that does not work, plug off the wheel motor hoses.
I'm also wondering if there might be some fluid leaking through the proportional valves for the other functions such as boom lift and extension and rotation? If there was even a little leakage, would that be enough to engage that function very slowly for example?
And kind of a dumb question since I haven't even tried it on the machine yet, but I'm wondering if you can engage two functions at the same time for example boom lift and extension or rotation, and if it just slows the function down when two of them operate at the same time?
Rotary manifold has top part and bottom part, it’s impossible to get to the bottom part without getting underneath of machine. But as far as i know there’s not supposed to be any other components between main control valve and rotary manifold, so you can tap in and plug right at outlet port of MAin Control Valve.
If you gonna have to work on bottom part of manifold I would suggest to drain your hydraulic oil tank and plug the case drain hose on top and drive hoses. The last one I worked on would not stop leaking from those, and I got covered in hyd. Oil from head to undies while I was laying underneath of the machine.
If you gonna have to work on bottom part of manifold I would suggest to drain your hydraulic oil tank and plug the case drain hose on top and drive hoses. The last one I worked on would not stop leaking from those, and I got covered in hyd. Oil from head to undies while I was laying underneath of the machine.
When you using two functions simultaneously it will slow down both, I didn’t see any load check valves in the diagram - so using function with very light load on may cause the function with bigger load to slow down, stop and even “sag” or down drift.
Thanks for that great advice TVA! And sorry to hear about your getting soaked with hydraulic oil.
That was a great explanation about wheel motor torque and speed as it relates to fluid volume and pressure. So let me ask you this question, when the hydraulic motor swashplate is tilted to the maximum 17-degree maximum position, that allows more flow, so my question is should the wheels be turning faster, but with less torque with this swash plate in the maximum 17 degree position, and be turning slower, but with more torque in the 3 degree nearly perpendicular closed position and allowing less fluid volume, but higher pressure, and better able for the wheels to climb over that 4 x 4 piece of wood that Bus talked about?
That was a great explanation about wheel motor torque and speed as it relates to fluid volume and pressure. So let me ask you this question, when the hydraulic motor swashplate is tilted to the maximum 17-degree maximum position, that allows more flow, so my question is should the wheels be turning faster, but with less torque with this swash plate in the maximum 17 degree position, and be turning slower, but with more torque in the 3 degree nearly perpendicular closed position and allowing less fluid volume, but higher pressure, and better able for the wheels to climb over that 4 x 4 piece of wood that Bus talked about?