Harold Hudson
Member
The guy came out just took the rams back with him the put them back in.
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D8H
- Thread starter Harold Hudson
- Start date
Harold Hudson
Member
Old Magnet
Senior Member
OK, based on the picture of your Hydraulic Control and 36A4099 s/n you have a model 36Exxxx front mounted Hydraulic Control. Single valve in the tank and a remote control valve for the tilt cylinder.
Attached are parts diagrams for the Quick Drop Valves. There are three valves in the QD housing that need to be checked out (movement and sealing). Also a parts diagram for the typical lift cylinder.
Not likely there is a problem with the main control valve if you are able to make down pressure although spool and bore wear could be a factor.
End of travel (cushion valves) in the piston could be a source of problems and leakage in one direction.
Others please comment.....
Attached are parts diagrams for the Quick Drop Valves. There are three valves in the QD housing that need to be checked out (movement and sealing). Also a parts diagram for the typical lift cylinder.
Not likely there is a problem with the main control valve if you are able to make down pressure although spool and bore wear could be a factor.
End of travel (cushion valves) in the piston could be a source of problems and leakage in one direction.
Others please comment.....
When we were fighting with the hydraulic shop we swapped the lines- if it was the control valve it should have done the same thing but opposite directions, but same result, pull back down & hold push forward up and then drop, so cylinders.
d9gdon
Senior Member
The problem I had was the end of travel valves in the piston as shown in the drawing.
My blade would lift but would immediately drift down like it had air in the system.
His problem sounds more like a problem in the QD valves. I think I'd first suspect a broken spring in the check valve allowing a bypass.
My blade would lift but would immediately drift down like it had air in the system.
His problem sounds more like a problem in the QD valves. I think I'd first suspect a broken spring in the check valve allowing a bypass.
Old Magnet
Senior Member
It's a little tricky.
In the raise position the check valve is cut out of the circuit by a "working" flow control valve.
In the raise position the check valve is cut out of the circuit by a "working" flow control valve.
d9gdon
Senior Member
If I were troubleshooting, I'd make sure I had pressure oil to the lift cylinders in the "raise" position first.
Looks to me like if the flow control valve spring broke or if the valve was stuck open by a piece of debris, pressure oil would just flow in a circle without lifting the blade. I question if only one "open" flow control valve in one lift cylinder (no chance in hell both cylinders have trouble) would bypass all the pressure oil that the pump could put out. Should be a quick check to find out.
If all is good there, I'd look at those end of travel valves on the pistons.
Looks to me like if the flow control valve spring broke or if the valve was stuck open by a piece of debris, pressure oil would just flow in a circle without lifting the blade. I question if only one "open" flow control valve in one lift cylinder (no chance in hell both cylinders have trouble) would bypass all the pressure oil that the pump could put out. Should be a quick check to find out.
If all is good there, I'd look at those end of travel valves on the pistons.
Old Magnet
Senior Member
Yes, it would have to be a good sized leak, it uses a 100 gpm pump.
OzDozer
Senior Member
Many years ago, I had a tiny chip of stray metal, about 1/16" wide and thick, and about 1/8" long, become tightly jammed under the main hydraulic relief valve of one of my D6C's.
Despite the relief valve being barely propped open, that little chip lodged in there ensured that the total output from the main hydraulic pump was dumped, and I could not get a single hydraulic cylinder to operate, either on the blade or the ripper.
Can't recall the exact output of the D6C hydraulic pump, but it was fairly substantial. It just blew me away that so much oil could go through such a small orifice, and totally prevent the operation of any cylinder.
Despite the relief valve being barely propped open, that little chip lodged in there ensured that the total output from the main hydraulic pump was dumped, and I could not get a single hydraulic cylinder to operate, either on the blade or the ripper.
Can't recall the exact output of the D6C hydraulic pump, but it was fairly substantial. It just blew me away that so much oil could go through such a small orifice, and totally prevent the operation of any cylinder.
Old Magnet
Senior Member
OK, I believe pressure is the key. If the pressure is low in the raise position the flow control valves in both lift cylinder quick drop valves can bypass fluid (big leak). As this supposedly came on rather sudden these "old timers" are somewhat famous for a fatigued/broken pressure relief valve spring (in the tank).
d9gdon
Senior Member
Yes, I could see that happening. That would eliminate my scenario of an open flow control valve in only one cylinder since the low pressure would allow both to stay open due to lack of pressure.
Harold Hudson
Member
Hello, sorry for not responding, was feeling bad. So does anyone have pic of pressure valve in the tank or just explain we're it's at. Thanks again for support! Harold
Old Magnet
Senior Member
You need to run a pressure test on the system before going into the tank.
Harold Hudson
Member
Just wanted to update. In the top of cylinder is 4 values one was stuck in place would not move had to drive out to unfreeze and polish it. Had to polish spool also, it lifts blade now. Thanks for helping, Harold.
Harold Hudson
Member
When working the clutch assist will not engage no matter how hard you pull. You have to idle down rpms then it will engage. Next it may work couple times, then it will get hard and not engage. Sometimes it not so hard but will pull in, but hard. This of course is the manual transmission. Clutch is not slipping, will spin tracks. Harold
John C.
Senior Member
The clutch in a direct drive machine has oil and a boost pump in the compartment along with a dipstick. The older direct drives that I worked on had a dipstick under a removable piece of deck plate over by the right side brake pedal as I recall. Most of the direct drive machines leaked oil around the case but you couldn't see it because of the dirt packed in the belly pan underneath.
Harold Hudson
Member
I checked oil already thinking it was low, it wasn't. What don't understand is it works one or two shifts then doesn't. I have to idle down then it will pull in. Sometimes it little hard but pulls in, other times you can't get in. Any ideas?
John C.
Senior Member
All the the dozer clutches I worked on had a cover you could remove on top that would allow you to look at the internal linkages. You can open that up and look at the movements inside with the engine shut down maybe to see if there are problems.
OzDozer
Senior Member
This is a new one on me - but as it is an erratic problem, I'd suggest a fastener of some type has come loose in the linkage, allowing enough movement of what it is supposed to be clamping to create interference with other components. The erratic style indicates something is moving out of whack on an irregular basis.
It could also be a failing bearing, with the shaft support provided by the bearing altering as it collapses.
It could also be a failing bearing, with the shaft support provided by the bearing altering as it collapses.