D5m priority valve pressure loss

[Mobiltech]

I think you will end up pulling the final drives and steering clutches. The steering clutches are oil applied so when you pull the lever you are dumping the pressure.
You will probably find the seals in the steering cutch failed and you can also inspect the tubes while you have the clutches out.

 

[Northpoint]

Ok, I tested both the Inlet torque pressure 130psi high idle on the priority valve and the outlet on the torque relief valve 110 psi high idle.
I removed 2 track shoes so I could get to the rest ports on top of the left steer/brake housing on the final drive. Tested the left steer port and removed the transmission fill cap above, inserted my air house to the test port and held my hand on the 2" fill opening and the air just pressurised the bevel gear oil reservoir.
I would think that test port should hold 300psi before spilling to the reservoir. I was just holding the air pressure with my hand and it pressured the transmission reservoir.
What do you think?

 

[Nige]

Ok, I tested both the Inlet torque pressure 130psi high idle on the priority valve and the outlet on the torque relief valve 110 psi high idle.

130psi maximum with cold oil at HI is the spec IIRC. Did you test the outlet pressure with the converter stalled against the brakes in 3rd speed and with everything at normal operating temperature.? 110 psi sounds awfully high, I would have expected somewhere in the range 50-60. The spec will be in the manual.

 

[Northpoint]

I just tested it now after warming it up again high idle 3rd speed with holding foot brake. It's about 75psi outlet.

 

[Northpoint]

130psi maximum with cold oil at HI is the spec IIRC. Did you test the outlet pressure with the converter stalled against the brakes in 3rd speed and with everything at normal operating temperature.? 110 psi sounds awfully high, I would have expected somewhere in the range 50-60. The spec will be in the manual.

I did test the torque output again after reading your post, after warming up the machine, the output pressure in 3rd gear high idle was about 70- 75 psi.
What I would like to know and you may not know the answer, is when testing the steer clutch at the final drive steering test port, should it hold pressure from a air gun and not just flow right out of the bevel gear case fill tube as mine does? I also had someone pull back the left steer lever, which made no difference in the pressure coming out of the fill tube. I would think it should hold some amount of pressure.
Thanks

 

[Nige]

I just tested it now after warming it up again high idle 3rd speed with holding foot brake. It's about 75psi outlet.

Spec is 68±10 psi so that's about right. Maybe a bit towards the high end of the range but so is the inlet pressure so not exactly unexpected.

 

[Northpoint]

Spec is 68±10 psi so that's about right. Maybe a bit towards the high end of the range but so is the inlet pressure so not exactly unexpected.

Thank you for your input Nige-

 

[Northpoint]

Spec is 68±10 psi so that's about right. Maybe a bit towards the high end of the range but so is the inlet pressure so not exactly unexpected.

I tried another method of testing the steer clutches before taking them apart. I used my air leak down tester on the left and right steer clutch test port above on the final drive. They both had exactly the same leak down 84%, meaning I believe they both have an exact same size bleed hole in there pistons for when you shut the machine down it releases the clutches pressure. That's my theory anyway. The system operations section does not go into it that deep.
If the steer clutches had a problem, I would think the leak down would be different from each side.?
Thinking my trans oil leak is coming from maybe the tube that go's from the priority valve to the steer/brake valve is cracked as Nige mentioned. Now to figure out how to test that.

 

[Nige]

Thinking my trans oil leak is coming from maybe the tube that go's from the priority valve to the steer/brake valve is cracked as Nige mentioned. Now to figure out how to test that

You would need both valves removed and fabricate blank plates to go over the ports that seal 100%. One plate would need a fitting on it to allow you to pressurize the tube. Apply shop air pressure and check if it holds or leaks off.

 

[Mquinista]

I tried another method of testing the steer clutches before taking them apart. I used my air leak down tester on the left and right steer clutch test port above on the final drive. They both had exactly the same leak down 84%, meaning I believe they both have an exact same size bleed hole in there pistons for when you shut the machine down it releases the clutches pressure. That's my theory anyway. The system operations section does not go into it that deep.
If the steer clutches had a problem, I would think the leak down would be different from each side.?
Thinking my trans oil leak is coming from maybe the tube that go's from the priority valve to the steer/brake valve is cracked as Nige mentioned. Now to figure out how to test that.

Since u are in such a deep troubleshooting efford, remind us, the reason of your problems started by the machine not engaging, or having problems engaging when hot, and NOT steering, would it be so out of the box checking the TXM operation with the steering system bypassed? so as the braking system?
Blocking the PV to the steering/brake side would do it. Despite it need pressure in Brake system to "walk" that would not be a problem to check press at P1 and P2 ports and rule out TXM clutches system leakage.

BTW driving the machine up slope or dwn slope , side slope or anyother slope would not starve any of the clutches of lube oil, no more than it would in a flat spot, as this lube is coming from same pump intake. Unless u have a really really low oil level, or other issue in lube system.
Either way pump would cavitate so much that it would not be unherdable and machine would get stuck imediatly. just my opinion.

nice job u´re doing,

 

[Northpoint]

Since u are in such a deep troubleshooting efford, remind us, the reason of your problems started by the machine not engaging, or having problems engaging when hot, and NOT steering, would it be so out of the box checking the TXM operation with the steering system bypassed? so as the braking system?
Blocking the PV to the steering/brake side would do it. Despite it need pressure in Brake system to "walk" that would not be a problem to check press at P1 and P2 ports and rule out TXM clutches system leakage.

BTW driving the machine up slope or dwn slope , side slope or anyother slope would not starve any of the clutches of lube oil, no more than it would in a flat spot, as this lube is coming from same pump intake. Unless u have a really really low oil level, or other issue in lube system.
Either way pump would cavitate so much that it would not be unherdable and machine would get stuck imediatly. just my opinion.

nice job u´re doing,

There is a small note in the Cat manuals that when on steep slopes over 45* to be sure to overfill the transmission 15% of oil because the pump may starve of fluid.
And yes you would know if it was starving by its reaction by it being noisey or feeling it.
The reason for me going the steering and brake direction is if the priority test pressure is not at full pressure at low and high idle, you have a problem with the steer/brake side of things. You would start checking the transmission side of things if the priority pressure is good at low and high idle.
My priority pressure goes down to 200 psi at low idle after 1 hour of operation and then will not shift. If I pull 1 of the steer levers the priority goes to full pressure. The priority valve only gives the transmission it's needed 425psi only after it gives the steer/brake valve it's full psi.
So no need to block off the steer/brake valve side when you understand how it works. Besides that it would be a monumental project to make a block off plate to test it as you suggested.
Thanks-

 

[Northpoint]

Update- The attached photo is inside the bevel gear housing while the machine is running at low idle, I used a camera with a light to be able to get this photo and I also have video that may be to large to post here. I wanted to see if the tube that supply's the steer/brake valve was spraying or leaking without having to remove the priority and steer/brake valves and make test plates to pressure test.
What your looking at is the tubing to the steer/brake valve inside the bevel gear case. The tube that looks red or dark in color in the middle of the picture is the return to tank tube from the steer/brake valve that has oil flowing out when the pressures are below the check valve psi values. I have other video and pictures of that flowing oil out. That tube actually rises up to about 6" vertical and is just a open tube at the top to where the oil just flows out from the top.
Question is, should there be oil flowing from that valve when it is not at the required pressures for the steer and brake spools? I would think it should not until it reached the required pressures set by the shims.
I have other video and photos of the tubes from the priority valve that shows no leaks or any spraying.
What do you think Nige? The tube below the one that is leaking oil is the pressure tube from the priority valve.

 

[Nige]

I dunno what to think. If I was stood next to the tractor what I would be trying to do is work out the function of each tube and where it carried oil to/from. Never having seen one of these in the flesh it's hard to comment. Even if it was a bigger tractor like the ones I am more familiar with I would still go back to first principles and trace where fluid was going to/from, etc.

 

[Northpoint]

I do understand what each tube does in this picture because I have studied the diagrams of the valves out of the service and parts manuals. My method of using a camera saves a lot of time from having to take things apart.
Now I will take apart the spools out of the steer/brake valve and see if there is any debris in one of the orifices.
Using the camera through the transmission fill tube will only work for seeing a few suspected problems in the gear case and is not a solution for seeing other problems. It just so happens that in this machine the steer/brake valve and priority valve tubes can be seen from the end of the fill tube while it's running and if there was a split tube you would be able to see it spraying or dripping oil.

 

[Mquinista]

I do understand what each tube does in this picture because I have studied the diagrams of the valves out of the service and parts manuals. My method of using a camera saves a lot of time from having to take things apart.
Now I will take apart the spools out of the steer/brake valve and see if there is any debris in one of the orifices.
Using the camera through the transmission fill tube will only work for seeing a few suspected problems in the gear case and is not a solution for seeing other problems. It just so happens that in this machine the steer/brake valve and priority valve tubes can be seen from the end of the fill tube while it's running and if there was a split tube you would be able to see it spraying or dripping oil.

Any developments?

 

[Northpoint]

Update- Did not find any problems with the steer/brake valve, no debris in it.
So here is what Cat does not tell you in there books and after talking to more then a half dozen Cat technical people, which none of them know how to test the steer/brake system.
I found the smoking gun of the problem with my steer/brake system. At lest I believe I have. When I had the steer/brake valve off the bevel gear case, I used my shop air hose and blew air in the right and left tubes for steer and brake tubes (4 of them). The right side held pressure and blew the tip of the blow gun back at me for both the steer and brake tubes, the left side blew all of the air pressure out the trans fill tube for both the steer and the brake tubes. So that's my smoking gun.
So I put the steer/brake valve back on and wanted to know if you could test it with the valve on the machine.
I hooked up to the test ports on the steer/ brake valve for just the right and left steer. You can only test this with the machine off. You have to pull back both steer/brake levers to where they begin pulling the brakes spools, this is what makes the two sides completely independent for testing the steer clutches and it also works for the brakes as lo g as you pull the levers back far enough. Put air pressure in the test ports to see how well each side holds air. You could use a leak down test also. Mine just blew air right in and out of the trans fill tube.
So the order of testing is if the priorty pressure is low, the problem is on the steer/ clutch system.
If the priority pressure is always at its required pressure and you still have problems it's in the transmission side of things.
Hope this helps someone.

 

[Nige]

So the order of testing is if the priority pressure is low, the problem is on the steer/ clutch system.

I’m glad that you have got to the bottom of the problem but more than one person has been trying to tell you to look at the steering/brake system from very early on.

 

[Northpoint]

Besides you Nige, there was only 1 other person that had a comment on this thread of what it probably would be, but did not have a method of testing it and that was only a few weeks ago, not early on. My method is an easy test that I would think Cat should have in there manual.
I've read other post on this forum to where they just replace everything without knowing what is really wrong and hoping it fixes it I did the same thing replacing my pump.
Question is, do I just rebuild the side that's bad or rebuild both sides. Could get a few more thousand hours on the good side, you just don't know.

 

[Nige]

there was only 1 other person that had a comment on this thread of what it probably would be,

And that was 3 weeks ago.

Personally I’d suggest that you rebuild both sides. If one has failed the other must be “tired” by now That’s why even though you didn’t know until now which side it was if you had pulled both sides at the start and rebuilt them the problem would have gone away.

 

[Mquinista]

So I put the steer/brake valve back on and wanted to know if you could test it with the valve on the machine.
I hooked up to the test ports on the steer/ brake valve for just the right and left steer. You can only test this with the machine off. You have to pull back both steer/brake levers to where they begin pulling the brakes spools, this is what makes the two sides completely independent for testing the steer clutches and it also works for the brakes as lo g as you pull the levers back far enough. Put air pressure in the test ports to see how well each side holds air. You could use a leak down test also. Mine just blew air right in and out of the trans fill tube.
So the order of testing is if the priorty pressure is low, the problem is on the steer/ clutch system.
If the priority pressure is always at its required pressure and you still have problems it's in the transmission side of things.
Hope this helps someone.

If I got it correctly , u had the brake/clutch valve assy off the tractor and found no evidence of a problem? and still the right and left side of this dual valve system behaves diff and sound to be the problem in your dozer?

This weekend i plan to look a my dozer, and the idea was to remove the TXM pump and send it for testing and repair if needed, but in this case i´ll also look at the priority valve pressures and the Brake clutch Valve system to see if it mimics your finding.
As i mentioned before, i´ve seen people complaining of this very same problem in this era machines here and other forums, with apparently no solution.