I recently purchased a D6D and I am having issues with the blade lift speed. All functions perform as they should , but the blade lift is slower than what it should be. We have changed fluids , filters and hydraulic pump(new pump) It may have helped a little , but it is still slower lifting than it should be. We have another D6D and the blade lift is much faster. If you push the blade down it will lift the tractor and hold , and it you lift the blade up it will stay up. It is just slow. Any other things I am missing? We also adjusted the linkage some. No visible leaks.
How much slop in the linkages as there are a heap of them.
Not much, we also took it off in the engine compartment and moved the lever by hand , and it did not change anything.
Have you measured any pressures in the implement hydraulic system.? Does the blade have hydraulic tilt.? If so is that working OK.?
We have not measured any pressures yet. It does have tilt. If you tilt to the right, it is jerky one time then doesn’t do it again works fine after that.
The jerky to the right is random. Doesn’t happen often.
Being that it’s jerky and you changed the pump, is there any chance the hydraulics have air or sucking air? Is there a suction screen in the hydraulic tank?
Yes, there is a screen in the tank. We changed that as well.
Could still be an indication that something is off somewhere. Is there any visible aeration of the oil in the tank.? Also are there any hydraulic leaks around the tank/pump area.?
We haven't looked into that yet.
No visible leaks that we can see.
It sounds like there is a relief valve in the tank that is bad? Any ideas on where to order a new one?
I think you will find the old relief valves were rebuildable a new needle and seat and a new spring and a couple of o rings and you will be like new
Is there a plate with a Serial Number fixed to the outside of the hydraulic tank.? If not please provide the machine Serial Number. We'll see where that takes us.
I think ??? there is 2 oil filters in the D6C and D hydraulic tank worth checking.
One oil filter with two elements in there.
4X-06180 is serial number. I haven’t checked tank yet. We are going to start working on pulling tank tomorrow.
As I suspected nothing for the hydraulic system listed under the machine Serial Number. It'll need the Hydraulic Control S/N (likely a model 163 of some flavour or another) from the plate on the tank.
Ok. I’ll get that!!
Strange that. Mine is older yet I get the full hydraulic breakdown just from the tractor S/N on SIS and it is in the parts book as well.
There are various tank setups, but none of them correspond to the machine S/N as posted by the OP. I suppose it begs the question is the S/N 4X6180 correct.?
Hydraulic controls earlier than s/n 4x6608 use the 39Gxxxx units for blade and tilt applications.
That is what I men't to say as the filter elements sit on top of each other, people remove the filter top and remove the upper most filter not knowing about the lower filter.
The serial number on the tank is 8X-5105. Picture is attached below.
That number seems to come up OK.
It looks as though the valve is not rebuildable. Attached the complete parts breakdown of the tank just in case you find you need any other parts once you get in there.
Thanks a bunch!!! We should have the tank out today. Is is required to take the dash out to get the tank out? It looks like it may come out the right (passenger) side without taking the dash out?
I guess that Didn’t make sense lol. Right side if in seat.
Better way of saying things would be one filter housing with 2 filters possibly inside stacked.
To remove the Hydraulic Tank on a D6 is a bit of work I would be double checking your facts before stripping the tank out, firstly I cannot recall a suction screen filter inside the tank, just a pipe that is well off the tank bottom with holes in it, you said that you had replaced the suction filter? there is an elbow cast fitting on the outside of the tank that has a small plug on the top of it to carry out a Pressure test (T Test), I would check the pressure on both the lift and tilt first, there is also an Anti Cav' valve on the valve block that could be a problem, if the blade lifts, holds and does not drop also will lift the Tractor when pressing down the blade the main valve is most probably good, the pressure test will rule out any problems with the Main Relief, I think the max pressure is around 2250 psi (not checked this fact), you test all functions of blade and tilt to verify the Main Relief, there is the thought that something could be loose on the Blade spool as there is detents on the float position, the Anti Cavitation valve could be allowing oil back to tank its simple to strip out when the tank is open, the hydraulic pump if I recall is around the 50 U.S. gallon per min at low to no pressure High Idle, the tanks are mounted on to brackets that usually involve lots of shim packers and nasty bolts that turn about 1 flat at a time.
I stated incorrectly. We only changed the filters in tank , not a screen at bottom of tank. Did you say the anti cav valve is in the tank as well? Or where is it located?
Going back to your symptoms...if all functions are working correctly but it is just slow I'd be looking to see that you are getting proper spool travel.
The Anti Cavitation valve is fixed to the side of the spool block inside the tank, it was also called the Make Up Valve but it is the same thing, the main relief is by the return to tank pipe, there is a check valve on both the tilt and hoist spools that are behind plugs at the bottom of the valve block, the blade hoist spool could possibly come unscrewed at 1 end but I have it in my head that the spool pulls down to hoist and gets pushed up to go into Float position but I might be wrong, the anti cav valve test used to be nothing more than lifting the front of the Tractor right up and letting the control lever go into the hold position, anyhow if you follow the pressure pipe from the pump to the tank you will see the bolted elbow with a plug on the top, remove this plug and mount your test gauge line into the hole, it's best to use a 3'000 psi gauge or a 4'000 psi at max for the best pressure test result on hoist rod in and tilt.
Got the dozer put back together yesterday. Turns out it was the relief valve in the tank. Kind of a booger to get the tank in and out, but other than that no issues. We pulled the tank out of the right side, and did not have to pull the dash. The original relief valve was in tank stamped 9-79- and was stuck open. Thanks a bunch for all the info and help, I appreciate it!!!