D35 Hydraulic Pressure Problem(s)

   / D35 Hydraulic Pressure Problem(s) #1  

gwin

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Jun 21, 2006
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Well, after reading many posts I worked on my hydraulics. That was not a problem. Wanting faster results was. I will describe what happened how I fixed it and then what I still need help with. And if anybody out there wants to give your 2 cents that would be great.

Original Problem: In 100+ degrees I was loading my neighbors dump truck. It was taking 7 bucket scoops to fill his dump. On all loads, as I approached the truck I would raise the loader and rotate the bucket forward to keep it level until I was over the bed then I would dump and go for another bucket scoop.

On the 5th and 6th truck loads the loader would only raise 3/4 of it's full height and would sometimes go higher only if the bucket was curled all the way back and sometimes it would not go higher at all.

I was at 270 hours so I changed oil and filter since I had done a lot of loader work and I thought the oil could be foaming with that much work and with the weather so hot. The following week same temperature outside and same results from the loader on the 5th and 6th truck loads.

I put a 3000 psi gauge in the remotes and got 2375 psi. Next 100+ degree day I was moving pipe with the loader. I put the gauge in the remotes and it read 2100 psi.

So with the hydraulics hot and the gauge reading 2100 psi I decided to shim the relief valve to 2500 psi. The relief had two 0040 shims and four 0010 shims. I added one 0010 shim and got 2200 psi on the gauge. I installed another 0010 with no change. Another 0010 shim got a drop to 1500 to 1700 psi. I removed all shims and installed the original configuration of shims and still got the 1500 to 1700 psi. I started adding shims again, (this time without calipers in hand), and I started stacking them until I had to compress the spring on the relief valve to install it. When I energized the remote to check the gauge I heard a pop and that was the hydraulic pump case. Pictures below show that crack.

I put shims back to original configuration,installed a new pump and bought a new 0-5000 psi gauge.

Problem Now: Gauge at remote reads 1800 psi @ 2500 rpm. Loader and bucket move with same speed it has had since new. I have not tried to scoop gravel, but it moves and operates fine in that regard.

Questions Now: Could I have damage the relief valve early on when the gauge first dropped to 1500-1700 psi? Is there a port in the distribution block to test the relief valve? Does the manual state a minimum and maximum number of shims? In the online parts manual the relief valve shows a ball or cap separate in the cone part of the relief valve body. Mine is stationary is it suppose to be removable? Any help would be appreciated.

Thanks all,
Clay
 

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   / D35 Hydraulic Pressure Problem(s) #2  
Thank you for having the courage to make this post. I am going to keep this post in mind and link to it anytime I am advising someone with a 35D to NOT try and adjust up the pressure of their hydraulics. I'm also not going to lecture you. You have suffered the consequences and I'll leave it at that.

THe shims are actually 0.3 mm (0.012 in) and 0.1 mm (0.004 in). You made a decimal point error in saying "0010" shim. That sould be "0120" since that is the bigger shim. That would make four thick shims and two thin ones. Is that what you started with?

I don't know why your tractor reacted the way it did. One thick shim is supposed to raise the pressure 150 psi. The fact that it only raised yours 100 psi would indicated there are other issues with your tractor that are causing loss of pressure. You could have a seal leaking slightly somewhere that is leaking more when hot that when the oil is cold. If that is the case, when you overpressured the system and the pump blew, you could also have caused this leak to degrade to the point that it is causing your low pressure now. If you have 1800 psi to your 3PH and loader, you will probably not notice too much difference until you get a very heavy load on as you did originally.

Where might the leak be? I think you have to consider the diverter valve and relief valve for sure. Is it possible the relief valve's seat was cracked by adding too many shims? Hard to say... The FEL joystick valve would also be suspect and may have been the problem all along. This is a daunting problem caused by a large overpressure spike. You have to consider everything that is exposed to that. The hardest to get to is the HPL valve for the 3PH and that is the one I would save for last. I think I'd look first at trash or damage to the diverter valve and then look at the joystick valve before tackling the HPL valve.

Good luck. I hope you find your problem and get your tractor back up to spec soon. BTW: The spec pressure for your hydraulics is 2275 psi, so the cold pressure of 2375 you read is slightly high.

EDIT: Your question about the relief valve port: Yes, the port right in front of the diverter valve ( the one with the screw head) is used to check pressure. In order to do that, you have to move the diverter valve screw slot from the 10 oclock position to the 2 oclock position. This eliminates the joystick valve. It's a lot easier to use the remotes or the front FEL ports to check pressure.

DANG! One more thing...
Check that pressure gage on a known pressure. That could have been your entire problem all along. Even though it is new, you don't really know how accurate it is. At this point you have to suspect everything.

Ha! Ha! Ol' guy = slow thinker.:eek:
The relief valve spring was probably damaged (overcompressed) when you over stacked the shims. Get a new relief valve spring before trying something else.

I'll probably be back with another idea or two. These things just hit me out of the blue.:)
 
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   / D35 Hydraulic Pressure Problem(s)
  • Thread Starter
#3  
Jim,

THe shims are actually 0.3 mm (0.012 in) and 0.1 mm (0.004 in). You made a decimal point error in saying "0010" shim. That sould be "0120" since that is the bigger shim. That would make four thick shims and two thin ones. Is that what you started with?

No, I started with 2 (0.040 or forty thousands) and 4 (0.0085 or eight and a half thousands). The larger ones were washers the smaller ones looked like purpose shims.

Check that pressure gage on a known pressure. That could have been your entire problem all along. Even though it is new, you don't really know how accurate it is. At this point you have to suspect everything.

I did that by replaceing the 3000 psi I was using with a store bought 5000.

I'll swing by case and order the spring tomorrow, that is a good idea.

Clay
 
   / D35 Hydraulic Pressure Problem(s)
  • Thread Starter
#4  
One more thought on shimming the relief valve. I just noticed in the parts catalog that the D35hp and D40hp-45hp have different part numbers for the relief valve assembly as well as for the distribution block. If the distribution blocks are different maybe there is no way to shim the 35hp's to 2500psi like the 40hp-45hp! Point being, maybe that is why I only showed a little gain then no gain before I tweeked something and went backwards.

Clay
 
   / D35 Hydraulic Pressure Problem(s) #5  
When you grenade a pump, all those little metal pieces end up somewhere. If you didn't clean the pressure hose from the pump, guess where they are now. I have seen grenaded pumps cause hydraulic issues for months.
Your original issue was probably cavitation. I would go to the next heavier weight oil.
 
   / D35 Hydraulic Pressure Problem(s)
  • Thread Starter
#6  
I agree that changing oil would have solved the original problem. In looking at UTF that are replacements for Hytran Ultra, I am struck at how low the operating temperature is for Hytran at 122 degrees Fahrenheit as opposed to Shell products at 170 and 190 degrees Fahrenheit. Hopefully, the oil that gushed out of the crack took all of the metal with it. It was a crack with no big chunks missing. Where I am at now is where I was before I blew the pump, which is that I tweaked something, ( in the relief valve), that only allows it to build 1800 psi.

My dealership does not sell the individual components of the relief valve so I can not purchase the spring alone. The relief valve assembly runs just under $300.00. One thought I had was to take the diverter block to a hydraulic shop for a bench test. If it tested at 2275 psi I could move on looking for a leak as Jim mentioned before. But I should be mindful of what I spend figuring this out. 50.00 here and 25.00 there will add up and equal an hour or two at Case shop for troubleshooting.
 
 
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